INSTAAR Noon Seminar-Abstracts

20 Apr. Christophe Randin, INSTAAR and Swiss National Scientific Foundation Postdoctoral Fellow.
"Modeling past and future changes in vegetation distribution in mountain regions."

Mountain ecosystems are likely sensitive to global warming, owing to the reduction of area with increasing elevation Moreover, mountain systems may experience unprecedented rates of warming during the next century, two or three times higher than that records of the 20th century. In this context, species distribution models (SDM) have become important tools for rapid assessment of the impact of accelerated land use and climate change on the distribution plant species.

In the first part of this talk, I will present results from the Alps. Here I developed and tested new predictor variables for SDMs, specific to current and future geographic projections of plant species in a mountain system, using the Western Swiss Alps as model region. Since meso- and micro-topography are relevant to explain geographic patterns of plant species in mountain environments, I assessed the effect of scale on predictor variables and geographic projections of SDMs. I also developed a methodological framework of space-for-time evaluation and hindcasting to test the robustness of SDM when projected in a future changing climate.

Many SDM studies have investigated the potential impacts of climate change on the distribution of plant species, but few have attempted to constrain projections through plant dispersal limitations. Instead, most studies published so far have simplified dispersal as either unlimited or null. However, depending on the dispersal capacity of a species, landscape fragmentation, and the rate of climatic change, these assumptions can lead to serious over- or under underestimation of the future distribution of plant species. To quantify the discrepancies between simulations accounting for dispersal or not, I carried out projections of future distribution over the 21st century for 287 mountain plant species in the Western Swiss Alps with a cellular automaton. Results of future projections for the 21st century will be discussed in perspective of vegetation changes monitored during the 20th century.

Nevertheless improvements are still required to provide robust projections of SDMs in complex landscapes such as mountain systems. These empirical models have reached their limits at fine scale and high resolution and thus, they should be combined with mechanistic models and calibrated with process-based predictors. Present models give static, empirical results: they reveal where suitable habitats may be located in a climatically altered future, but they do not formally consider processes leading to these changes. Therefore, in the second part of this talk, I will present a new framework to test new process-based predictors in SDMs that are adapted to fine scale, high resolution and complex environments using climate and vegetation data from an alpine core research site on the Niwot Ridge saddle (3500 m elevation), located in the Colorado Front Range of the Rocky Mountains.

13 Apr. Waleed Abdalati, CIRES Earth Science and Observation Center.
"Recent changes in the Greenland Ice Sheet: Are we waking a sleeping giant?."

Satellite and airborne remote sensing techniques are revolutionizing our understanding of the Greenland and Antarctic ice sheets, revealing changes that are in some cases much more dramatic than were ever expected. From collapsing ice shelves to accelerating outlet glaciers, to increasingly negative ice sheet mass balance, remote sensing capabilities are providing important insights into ice sheet behavior. When coupled with in situ observations and robust process models, these large-scale four-dimensional observational capabilities are helping us understand the nature of the changing ice cover, the processes that govern it, and what the implications for the future may be. In particular, there are several capabilities that have enabled estimates of ice sheet contributions to sea level rise within the last decade. These include: airborne laser altimetry from the Airborne Topographic Mapper (ATM), satellite laser altimetry from the Ice Cloud and Land Elevation Satellite (ICESat), gravity change measurements made by the Gravity Recovery and Climate Experiment (GRACE), and discharge flux assessments derived from inteferometric synthetic aperture radar observations. I will review recent results produced by these different approaches, examine their strengths and limitations, and discuss new insights that satellites and aircraft are providing. In addition, I will discuss future satellite missions that are planned in order to help us understand the mechanisms and implications of changes in these great ice sheets.

06 Apr. John Hoffecker, INSTAAR.
"Starting over: Neanderthals and modern humans in Eastern Europe."

New perspectives—engendered by recent research both within and outside Eastern Europe—are emerging on the human settlement of this part of the world during the Pleistocene. Due presumably to low winter temperatures and/or reduced biological productivity, the immense East European Plain was the last major area of mid-latitude Europe occupied by humans. It was colonized by Neanderthals during the late Middle Pleistocene (their earlier sites dated primarily by soil-stratigraphic correlation). Both anatomical adaptations to cold climate and a diet rich in protein and fat derived from large mammals probably were critical to their success, and there is new evidence that the Neanderthals occupied an ecological niche with a special focus on super-herbivores—mammoth and woolly rhinoceros. Modern humans invaded the central plain of Eastern Europe prior to Heinrich Event 4. Extensive excavations at Kostenki on the Don River reveal a unique “human landscape” across which people moved and camped, providing a more complete picture of society and economy than the rockshelters of Western Europe. Modern humans created a new ecological niche for themselves, exploiting a variety of small vertebrates with innovative technologies for harvesting animal prey that apparently were inaccessible to the Neanderthals. The pattern of artifact variability at Kostenki provides a basis for reinterpreting the early-modern human record of Eastern Europe as a whole. During the early phases of the Last Glacial Maximum, modern human settlements on the central plain expanded to unprecedented size and complexity with a host of technological innovations.

30 Mar. John Andrews, INSTAAR.
"Variations in ice rafting in the northern North Atlantic over the last 12,000 cal yrs (Iceland, East Greenland, and Baffin Bay/Labrador Sea)."

ariations in the extent and severity of drift ice (that is sea ice and icebergs) is an important element in the Holocene climate of the North Atlantic region. Two large streams of drift ice impact the area. The first is largely sourced from the Arctic Ocean and is transported southward in the TransPolar Drift and the East Greenland Current. This source is of the order of 5000 km3 of sea ice and 50 km3 of icebergs. The second major source consists of a limited contribution from the Arctic Ocean via the Canadian High Arctic channels, plus sea ice formed in Baffin Bay, Hudson Bay, and along the Labrador margin and a much larger contribution from icebergs from SE-NW Greenland and the Canadian Arctic islands (ca 200 km3). One proxy for drift ice is the non-clay and clay mineral composition of marine sediments, obtained from quantitative X-ray diffraction analysis of the < 2 mm sediment fraction. This is most easily argued for the Iceland shelf where drift ice reaches the island via the East Greenland Current and its offshoot, the East Iceland Current and where quartz is virtually absent in the native volcanic sequences. However, in the marine sediments of N Iceland quartz weight% is shown to have a coherent signal. On the East Greenland margin the problem is more complex because of the varied geology along the coast and in some of the potential sediment source areas on the shallow shelves of the Arctic Ocean. In order to understand the sources and sinks along this margin I have run XRD analyses on suites of samples from the floor of the Laptev Sea, and slope to fjord transects at 73° and 70° (Scorsby Sund) in order to compare with data from cores between 68°-69° N. The final area is that of Baffin Bay and the Labrador Sea, areas that were affected by deglaciation of the Laurentide and Innuttian ice sheets between 12,000 and ~7,000 cal yr BP. Even today it is estimated that some 40,000 icebergs/yr are generated along the W/NW margin of the Greenland Ice Sheet. There are few sources of sea ice sediment in Baffin Bay but sea ice in Hudson Bay probably does contain a significant (but unmeasured) sediment load. A major mineral tracer is dolomite, which outcrops at the northern end of Baffin Bay. The dolomite:calcite ratio in Baffin Bay is ca 10:1 whereas sediments derived from Hudson Strait and Hudson Bay are dominated by calcite. This has the potential to allow us to distinguish between these two source areas at sites along the Labrador margin.

16 Mar. Tania Schoennagel, Dept of Geography.
"Causes and consequences of fire and insect outbreaks in Rocky Mountain Forests: implications for management and climate change."

Forest disturbances such as wildfire and mountain pine beetle (MPB) outbreaks are tightly linked to climate variability at local to hemispheric scales, and exert significant influences on landscape pattern and process. Some scientists argue that the magnitude, impact and sensitivity of such disturbances to climate change, may overshadow direct effects of temperature and precipitation on forest mortality. In this talk, I will present an overview of some of my research activities that address: 1) the influence of Pacific and Atlantic sea surface temperatures (represented by the El Nino Southern Oscillation and Pacific Decadal Oscillation; and the Atlantic Multidecadal Oscillation; respectively) and their temporal interactions on large subalpine forest fires across the Rockies, and 2) the effects of recent drought and climate warming on the development of the current MPB outbreak in western Colorado, which has affected 1.5 million acres of lodgepole pine since 1996. In addition to investigation of climatic influences on forest disturbances, I will also discuss ecological responses to wildfires drawing on empirical studies from the Colorado Front Range, with implications for management approaches to forest restoration and fire mitigation and in the wildland-urban interface.

09 Mar. Ben Cook, NOAA Global Change Postdoctoral Fellow and ATOC/ INSTAAR Candidate.
"Amplification of the North American ‘Dust Bowl’ drought through human induced land degradation."

The ‘Dust Bowl’ drought of the 1930s was highly unusual for North America, deviating from the typical pattern forced by ‘La Nina’ with the maximum drying in the central and northern Plains, warm temperature anomalies across almost the entire continent, and widespread dust storms. General circulation models (GCMs), forced by sea surface temperatures (SSTs) from the 1930s, produce a serious drought, but one that is centered in southwestern North America and without the warming centered in the middle of the continent. In a series of GCM experiments, we show that the inclusion of forcing from human land degradation during the period, in addition to the anomalous SSTs, is necessary to reproduce the anomalous features of the Dust Bowl drought. The degradation over the Great Plains is represented in the GCM as a reduction in vegetation cover and the addition of a soil dust aerosol source, both a consequence of crop failure. As a result of land surface feedbacks, the simulation of the drought is much improved when the new dust aerosol and vegetation boundary conditions are included. Vegetation reductions explain the high temperature anomaly over the northern U.S. (via a reduction in evapotranspiration and a shift from latent to sensible heating). The dust aerosols reduce net radiation at the surface and the top of the atmosphere, inducing upper level convergence and low level divergence. Anomalous subsidence develops, inhibiting convection and cloud development, intensifying the drought and moving it northward of the purely ocean-forced drought pattern. When both factors are included in the model simulations, the precipitation and temperature anomalies are of similar magnitude and in a similar location compared to the observations. Human-induced land degradation is likely to have not only contributed to the dust storms of the 1930s, but also amplified the drought and these together turned a modest SST-forced drought into one of the worst environmental disasters the U.S. has experienced.

02 Mar. Nicole Lovenduski, NOAA Global Change Postdoctoral Fellow and ATOC/ INSTAAR Candidate.
"The future of the Southern Ocean carbon dioxide sink."

The Southern Ocean currently serves as a sink for atmospheric carbon dioxide (CO2), but the strength of this sink has weakened over the past few decades. It has been suggested that the primary cause of the sink reduction is a trend in the position and intensity of the Southern Hemisphere westerlies and the subsequent increase in the upwelling of carbon-rich waters from below. The wind stress trend is likely to continue in the coming century, further weakening the Southern Ocean CO2 sink. However, the coming century may also be characterized by enhanced precipitation over the polar oceans, warmer surface temperatures, and enhanced melting of sea ice, leading to increased stratification and suppressed upwelling of carbon-rich waters in the Southern Ocean. The trends in stratification and wind stress will have competing influences on the future CO2 sink strength, and yet the net effect of these two processes is unknown. Here, I test the sensitivity of the Southern Ocean carbon sink to changes induced by wind stress and stratification using an idealized ocean general circulation and biogeochemical model.

27 Feb. Allegra LeGrande, ATOC/ INSTAAR Candidate.
"New insights into atmospheric hydrology from water isotope observations
(past and present) and modeling ."
Note Special Day, Time, Location, and Event: Friday 4:00 pm, Duane Physics 11th floor

The ratios of the distinct water isotopes (H216O='normal water', HDO, and H218O) in water reservoirs are excellent tracers of the hydrologic cycle. Heavy isotopes are discriminated against during evaporation, and concentrated in condensation, which results in very robust patterns global patterns of isotopic composition related to climate. Water isotope tracers are forward modeled in the fully coupled atmosphere-ocean general circulation model at GISS, ModelE-R.

Water isotope records collectively provide some of the most extensive proxy evidence for past climate from time scales ranging from annual to millions of years. The availability of the water isotopes in ModelE-R presents an excellent opportunity to constrain the model performance under a broad variety of climates. If comparisons to modern and proxy climate data are good, the model provides a means to acquire a better understanding of mechanisms of climate change.

Numerous ModelE-R simulations over the last 20,000 years are performed and evaluated using paleoclimate and modern data. These simulations reveal the primary mechanisms controlling both water isotopes and climate variability on various time scales. The suite of model tracers allows further evaluation of the relationship between climate and water isotopes, and is used to infer the relationship of water isotopes and climate over time.

The relationships between water isotopes and climate (i.e., surface air temperature, salinity, precipitation, etc.) are different at decadal timescales than at orbital (millennial) timescales and that this relationship also changes during abrupt climate change events. In particular, the modulation of the amount of water exported from the tropics, exchanged between ocean basins, and drawn onto land has profound impacts water isotopes distribution and their relationship climate. We find that the relationship between water isotopes and climate is likely not constant through time, possibly altering the interpretation of past climate based on water isotope reconstructions. For instance, tropical variability in oxygen isotopes over China do not co-vary with precipitation, and temperature variability at Summit can be masked by the lack of oxygen isotope variability there, though the model simulation of water isotope distribution at both places compares favorably with data. Despite these complications, robust patterns of change in water isotopes do exist, and indicate distinctive, inter-related patterns of climate change.

From 9,000 years ago until 6,500 years ago sea level changed from 40 meters below present to the modern level. Over this interval, the enormous ice sheet covering North America (called the Laurentide), started at ~twice the size of modern Greenland then completely disappeared. This time period presents an opportunity to examine the mechanisms quick ice sheet demise.

This period is simulated in ModelE-R and results are constrained against multiple water-isotope paleoclimate archives, yielding a range of uncertainty in the simulated climate. The coupled model is then used to drive an off-line Energy-Moisture Balance Model, with this range of uncertainty being better explored. The retreat rate (for ice model validation) in this case is known from geologic evidence taken from the margins, allowing the EMBM parameterizations to be improved. This technique lends itself to training ice sheet models to adequately simulate the demise of ice sheets of the past in the hopes that the future fate of the Greenland ice sheet can be better constrained.

Water isotope study is thus an important tool for providing insight into the hydrologic cycle of the past, present, and future.

23 Feb. John Behrendt, INSTAAR.
"From IGY to IPY: Volcanism associated with the West Antarctic Rift System interpreted from geophysical observations, and possible effects on the stability of the West Antarctic Ice Sheet (WAIS) ."

Observations from a few oversnow and airborne magnetic profiles acquired over the West Antarctic Ice Sheet (WAIS) during the International Geophysical Year (1957-58) indicated numerous high amplitude, shallow source, magnetic anomalies over a very extensive area of the presently known West Antarctic rift system. Aeromagnetic surveys over the WAIS in the early 1960s and later combined with radar ice sounding in 1978-79 defined this area as >500,000 km2; these anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick moving ice. Behrendt et al, (1962, 1964, 1994, and 2005) and Jankowski et al. (1983) interpreted these anomalies as indicating "volcanic centers."

Detailed aeromagnetic and radar ice sounding surveys since 1993 have shown that >80% of these anomaly sources at the bed of the WAIS have been modified by the moving ice into which they were injected requiring a younger age than the WAIS ( about 25 Ma). Behrendt et al., (1994; 2007) conservatively estimated >1 x 106 km3 volume of volcanic sources to account for the area of the "volcanic center" anomalies and suggested the presence of a large igneous province (LIP) if this volume was intruded within a time interval of 1-10 Ma.

Active volcanism at a few widely spaced exposures of alkaline volcanic rocks associated with the West Antarctic rift volcanic exposures, which extend in age to ~34 Ma in the WAIS area, and interpreted active subglacial volcanism revealed by aerogeophysical data (Blankenship et al., 1993; and Corr and Vaughan, 2008) have raised the question of possible volcanic effects on the regime of the WAIS. Vogel and Tulaczyk (2006) argued that subglacial volcanism may play a "crucial roll" in WAIS stability, but LeMasurier (2008) has discounted this as unlikely.

In my presentation I will review the geophysical evidence acquired from the IGY to the IPY, and conclude that whether unlikely or not, future effects on the stability of the WAIS should not be ignored.

16 Feb. James Syvitski, INSTAAR.
“The Community Surface Dynamics Modeling System (CSDMS) and what it means to INSTAAR."

The Community Surface Dynamics Modeling System (CSDMS) deals with the Earth's surface - the ever-changing, dynamic interface between lithosphere, hydrosphere, cryosphere, and atmosphere. We are a diverse community of experts promoting the modeling of earth surface processes by developing, supporting, and disseminating integrated software modules that predict the movement of fluids, and the flux (production, erosion, transport, and deposition) of sediment and solutes in landscapes and their sedimentary basins.

The project is now almost completing its second year, the framework is established, the models are coming in and new integrative research projects have started. CSDMS recently aqcuired a new supercmputing system, and more and more members have joined over these two years, among them a number of fellow INSTAARs.

Please join us for a talk to explore what CSDMS is all about and how you can get involved with the initiative.

09 Feb. Simon Mudd, INSTAAR/Geography Hydrology Candidate.
"The coupled geochemical and geomorphic evolution of soil mantled landscapes."

In many eroding landscapes, the most intense geomorphic and geochemical activity occurs within soils. Physical and geochemical processes determine the supply and export of mobile sediment, the form of the landscape, and the export and cycling of solutes and nutrients. It is not surprising that soils have been the focus of both geomorphic and geochemical research for decades, even centuries. Geomorphic studies have largely ignored geochemical processes, however, and similarly most geochemical studies of soils have neglected lateral sediment fluxes. Here the strong coupling between geomorphic and geochemical processes in eroding hillslope soils is explored. Hillslope soils are derived both locally, from underlying parent material, but also from sediment that has been transported from upslope. It will be shown that quantification of long term weathering rates in hillslope soils requires methods that account for this transport, and also how changes in geomorphic processes may lead to changes in geochemical processes. Geomorphic processes control the supply of fresh minerals to the soil, which can affect weathering rates. Because individual minerals can reside in the soil for many thousands of years, it is necessary to account for the history of geomorphic processes to understand mineral supply rates over the timescale of soil formation. Understanding the geomorphic history of a landscape is crucial for interpreting geochemical evidence of soil evolution; the evolution of soils in response to transient forcings due to tectonic and climatic change will be discussed. Finally, it will be demonstrated that hillslopes have three important timescales that determine how long evidence of past erosion rates may be stored on the hillslope. The implication of these timescales, ranging from thousands to millions of years, is that soils can potentially be used as recording devices to reconstruct both geomorphic and geochemical histories of eroding landscapes.

02 Feb. Stanley Deetz, Director, Peace and Conflict Studies, Department of Communication.
"Communication design for collaborative interaction with diverse publics."

Our contemporary context is characterized by a rapid increase in pluralism and interdependence and a shift in the sites where critical public decisions are made. To make mutually economically, ecologically and socially sustainable decisions requires new models of democratic decision making. INSTAAR and similar groups are at the front edge of community decision making and new cooperative forms of governance. Stakeholder governance models offer conceptions of how diverse value and interest inclusion in decisions might be rethought in light of these shifts. Communication has often been thought of in terms of informing, information distribution and education programs. These are valuable but often limited in long term effects.

Two problems stand out. Messages compete with long-term, commonsensical, and socially supported “native theories” of climate and ecological systems. And “native theories” of communication, democracy and governance produce rarely produce interactions that challenge these native theories and do not produce understandings or decisions sufficient for our shared situation.

The combination of needs for economic, social and ecological sustainability requires high degrees of creativity, multiple party commitment, unforced compliance and local need customization. We know of no way to get these without high participation and collaboration but all forms of participation, collaboration and communication or not alike. The discussion will focus on communication designs for the best forms of participation and collaboration.

26 Jan. Noah Molotch, INSTAAR/Geography Hydrology Candidate.
"Climate change at the edge of the cryosphere: integrating observations and models to understand the mountain water cycle."

Positioned at the edge of the cryosphere, the hydrology of mid-latitude mountainous regions is extremely sensitive to climate variability. As a top-down driver for this sensitivity, the mountain snowpack is the main source of water within these systems, with downstream hydrologic processes and interactions with ecosystems controlled by processes at higher elevations. Recent changes in climate and rapid population growth drive the need for new understanding of the processes that control snow accumulation and melt. Over rugged terrain, snow distribution is highly variable in time and space, motivating studies that merge models with observations acquired at multiple scales (e.g. using intensive field observations and remote sensing). Example applications will be presented in which hyper-spectral and multi-spectral remotely sensed data are used to reconstruct the distribution of snow water equivalent in watersheds of the Sierra Nevada and Rocky Mountains. Validated through comprehensive field campaigns, these high-resolution (i.e. ~ 100 m) snow estimates have improved our understanding of the processes that control snow distribution, providing estimates of snow water volume at unprecedented accuracy. This has transformed our ability to evaluate inter-annual trends in snow information, enabling the spatially explicit assessments needed to understand impacts to basin-scale hydrology and ecosystem response. In this regard, a variety of interdisciplinary research initiatives will be discussed in the context of understanding water and energy fluxes across Earth's cryosphere with an emphasis on linkages with glaciology, ecology, biogeochemistry, and landscape evolution.

06 Dec. Alan Townsend, INSTAAR.
"Catch 22: Global Nutrient Cycles and Human Welfare."

Humans have substantially altered the global cycles of nitrogen (N) and phosphorus (P), and continue to do so at accelerating rates. Even at a global scale, we have at least doubled inputs of biologically available N, and tripled those for P. The environmental consequences of such changes are diverse and growing, and include contributions to climate change, species loss, air pollution, fisheries decline, aquatic eutrophication and soil acidification. Of late, we’re also beginning to recognize that excess N and P in the environment can threaten human health, for reasons ranging from air and drinking water pollution, to shifts in the dynamics of infectious diseases.

Most of the changes to global N and P cycles are due to modern food production, which is a tale of two worlds. The wealthy one has blazed a path to an agricultural system that is typically nutrient-intensive and inefficient in the use of these key resources. The other world is one of a billion or more people trapped in cycles of malnutrition and poverty. Perhaps best exemplified by sub-Saharan Africa, these are regions where agricultural production is often insufficient to meet even basic caloric needs, let alone to provide a source of income. Here, severely eroded, poor-fertility soils are common, and an infusion of more fertilizers would clearly help.

The contrast of these two scenarios highlights the fundamental challenge of altered nutrient cycles: we need human-created N and P to feed the world, but we must also learn how to achieve that goal with greater efficiency and global equity, and lowered environmental impact. This talk will i) give a brief overview of how the global N and P cycles are changing; ii) discuss some of the consequences, with an emphasis on human health and welfare; and iii) finish with a few hopeful examples of how we might chart a more sustainable path. While the scale and pace of current changes to global nutrient cycles are unquestionably worrisome, it is also clear that we can retain many of the essential benefits of anthropogenic N and P while greatly reducing their risk.

01 Dec. Tom Stohlgren, US Geological Survey and Natural Resource Ecology Lab.
"Invasion ecology and NEON: Theory and scale."

Theories about plant invasions have been dominated by observations on islands and experiments in small (1-m2) vegetation plots. The resulting paradigm suggested that areas high in native species richness were less prone to invasion by non-native species. My colleagues and I sought to better understand the effects of spatial scale on patterns of invasion at local, regional, and national scales in the United States. Our results were surprising. Across a wide range of spatial scales, “the rich got richer” – areas of high native species richness were more heavily invaded than species-poor areas. But scale matters! Invasion patterns are inconclusive at small scales. However, at modest spatial scales (>100 m2), there was little sign of saturation (i.e., invasion by non-native species was likely to occur despite apparent competition from native species). In addition, there is little sign of saturation for state, regional or national floras in the USA where colonization (i.e. invasion by non-native species) exceeds extirpation by roughly a 24 to 1 margin. We also report an alarming spatial and temporal trend in “the human invader” in the conterminous United States from 1992 to 2001, including the rapid urbanization of forest and agricultural lands following predictable responses to climate and topography. There are many challenges related to invasion ecology, theory, and management: (1) harmful non-native plants, animals, and pathogens continue to spread globally; (2) hot spots of native diversity are often hot spots of invasion; (3) there is little sign of species saturation at regional scales; and (4) it is increasingly important to prevent, document, map, and predict harmful invading species to preserve native species and plant assemblages. The new National Ecological Observatory Network (NEON) may provide the ideal infrastructure to measure and monitor land cover change and invasive species under changing climates.

17 Nov. Alisa Mast, US Geological Survey.
"Mercury in the Front Range: from deposition in Loch Vale to fish in Horsetooth Reservoir."

The growing number of fish consumption advisories for Colorado reservoirs has increased concern about mercury contamination of aquatic ecosystems. Although atmospheric deposition is the likely source of mercury, watershed processes generally play a much greater role in the degree to which mercury accumulates in fish. Insights on mercury cycling learned using the small watershed approach at the Loch Vale Watershed in Rocky Mountain National park will be presented. Mercury in fish tissue collected in water bodies throughout Colorado also will be presented.

10 Nov. Mark Serreze, National Snow and Ice Data Center.
"The emergence of arctic amplification."

The concept of Arctic amplification is that rises in surface air temperature in response to increasing atmospheric greenhouse gas concentrations will be larger in the Arctic compared to the Northern Hemisphere as a whole. Model-projected Arctic amplification is focused over the Arctic Ocean. As the climate warms, the summer melt season lengthens and intensifies, leading to less sea ice at summer's end. Summertime absorption of solar energy in expanding open water areas increases the sensible heat content of the ocean. Ice formation in autumn and winter, important for insulating the warm ocean from the cooling atmosphere is delayed. This promotes enhanced upward heat fluxes, seen as strong warming at the surface and in the lower troposphere. Based on evidence from the NCEP and JRA-25 atmospheric reanalyses, the satellite-derived sea ice record and other data sources, Arctic amplification associated with declining ice extent has emerged in the past decade and is growing in strength. The extreme Arctic warmth of autumn 2007 and 2008 serves as an exclamation point on this trend. Anticipated impacts of continued Arctic amplification include alterations in patterns of atmospheric circulation and precipitation both within and beyond the Arctic, and enhanced warming of Arctic and subarctic land areas that may hasten carbon cycle feedbacks associated with thawing permafrost.

03 Nov. Doug Robertson, Dept of Geology and CIRES.
"Bernard Riemann and the most important unsolved problem in mathematics."

Bernard Riemann died on July 20, 1866, a few weeks short of his 40th birthday, and published only nine papers in his brief lifetime. It is difficult to overstate the importance of these nine papers. Gauss himself called Riemann's work "Beyond my expectations," and "Breathtakingly original," and Gauss did not live to see Riemann's most important work. This talk will give a brief survey of Riemann's work and will then focus on the Rieman Hypothesis. It will describe the Hypothesis itself and explain why it's proof is considered the most important unsolved problem in mathematics.

27 Oct. Astrid Lyså, Geological Survey of Norway, Visiting INSTAAR Researcher.
"The Weichselian glacial history of NW Russia: a complex interaction of different ice sheets and ice-dammed lakes."

The Arkhangelsk area west of the Timan ridge, northwest Russia, holds a geographical key position for studying glacier and lake history. During the Weichselian period, ice sheets from three different centers advanced into the area; the Scandinavian, the Barents Sea and the Kara Sea ice sheets. Sedimentological records demonstrate that these glaciers were not in phase and a rather complicated dynamic glacier system existed. The landscape in the area has a generally smooth topography. It is dominated by wide, gently northward dipping river valleys, except the areas nearby the ice-marginal zone where glacial landforms dominate. The major part of the Quaternary deposits is found in the deep paleo-valleys in which host stacked sediments of different origins, reflecting deposition during fluctuating climate, sea levels changes and lake-basin formation. The present rivers that drain northwards into the White Sea or Barents Sea have made up to 30-35 m incisions into the valley-fill and such river sections, in addition to coastal sections, have been investigated. As the glaciers grew and decayed several times during the Weichselian, formations of huge ice-dammed lakes took place. These lakes have likely been of the largest ice-dammed lakes ever known in the world. Until now, reconstructions of these lakes have mainly been based on ice-sheet configurations, timing and anticipated lake drainage routes. During the last couple of years, some lake sediments and morphological signatures of these former lakes have been found, although the distributions and pass-points still are under debate. New data from fieldwork in 2007 and 2008 will be presented in this talk.

20 Oct. Colleen Flanagan, National Park Service, Air Resources Division.
"Airborne contaminants found in National Park ecosystems: Findings and implications from the Western Airborne Contaminants Assessment Project (WACAP)."

According to the six-year, multi-agency Western Airborne Contaminants
Assessment Project (WACAP), numerous airborne contaminants, including
mercury and pesticides, were detected in twenty western US and Alaskan
national park ecosystems from the Arctic to the Mexican border. WACAP linked
atmospheric deposition with ecosystem effects, evaluating the risk to food webs
and probable sources of such contaminants through sampling of air, snow,
water, lake sediment, lichen, conifer needles, and fish in eight core parks,
including Denali and Rocky Mountain NPs. More limited assessment focusing on
vegetation was conducted in twelve secondary parks, including Great Sand
Dunes and North Cascades NPs.

Key findings from the core parks indicate that: (1) measureable amounts of
contaminants were found in every park sampled; (2) contaminants are carried in
air masses from sources as far away as Europe and Asia, and as close as the
local county; (3) parks nearest agricultural areas contained higher levels of
pesticides; (4) contaminants generally increased with elevation; (5) contaminant
concentrations of mercury, DDT, or chlordanes in fish exceeded risk thresholds
for health impacts to fish-eating birds and/or mammals; (6) concentrations of
mercury, dieldrin, and/or DDT found in fish exceeded EPA human health
thresholds; and (7) some "intersex" fish (male and female reproductive
structures in the same fish) were found; and (8) some emerging contaminants,
such as PBDEs, show increases in deposition.

Conducted from 2002 to 2007, WACAP results add considerably to the state of
the science concerning contaminant transport and subsequent biological and
ecological effects in remote western US and Alaskan ecosystems. Study findings
have been widely shared with federal and local agencies, as well as stakeholders,
resulting in follow-up initiatives to apply data and communicate WACAP results
for policy and research applications. The WACAP report, fact sheet, publications
and more can be accessed at
http://www.nature.nps.gov/air/Studies/air_toxics/wacap.cfm.

13 Oct. Randolph “Stick” Ware, Radiometrics Corporation Chief Scientist and NCAR Visiting Scientist.
"Arctic temperature, humidity and liquid profiling."

WeatherCam -- a hyperspectral microwave and infrared sensor -- monitors air temperature, humidity and liquid structures that define local weather. This passive microwave radiometer technology is proven during more than a decade of continuous operations at Barrow (Alaska, USA), Ny Alesund (Norway) and Eureka (Nunavut, Canada). Radiometer temperature and humidity profiles have comparable or better accuracy than co-temporal radiosonde data when used for numerical weather modeling, and up to ten times better accuracy than radiosondes with 12 hour latency. Dynamic exchange among water vapor, liquid and solid determines the evolution of atmospheric cloud and precipitation particles. Microwave radiometer profile measurements during snowstorms in the North American Central High Plains and Canadian Great Lakes regions were consistent with the Wegener-Bergeron-Findeisen process. Magnitude rankings of vapor pressures in-cloud, and equilibrium vapor pressures over liquid water and ice, identified simultaneous liquid droplet and ice particle growth or depletion, and droplet evaporation and ice particle growth by vapor diffusion. Case studies of winter snowstorms and severe convection, and live displays from international radiometer networks will be presented. WeatherCam observations of powder snow genesis at Boulder during the 14 Feb 2008 upslope snowstorm are presented.

06 Oct. Gaetano Di Achille, Laboratory for Atmospheric and Space Physics (LASP, CU-Boulder).
“Geology of Martian sedimentary deposits and paleolakes: a tool to study the history of water on the Red Planet."

Martian climatic history could have been more complex, locally variable and episodic than expected. Simplistic extrapolations from climatic models and scattered mineralogical observations are likely not adequate to reconstruct the overall hydrological evolution of Mars. Therefore, only detailed geological works and correlations across diverse areas can help to constrain the relationships between the coupled climatic and morphological evolutions of the planet. For instance, delta-like deposits, wave-cut terraces, and shorelines are fundamental features to support the hypothesis of standing and long-lived water bodies on Mars. Lakes, due to their relatively limited size and strong climatic coupling, might allow reconstruction of local hydrological cycles and help to better understand the Martian climatic evolution. Our recent works show that current data availability enable detailed analysis of complex lacustrine systems. I will present examples of such investigations and discuss their paleohydrological implications.

29 Sep. Suzanne Anderson, INSTAAR.
"Boulder Creek Critical Zone Observatory: A new approach to understanding the Earth's surface."

We live at the dynamic interface between the solid Earth and its outer fluid envelopes. This interface, extending from the outer vegetation canopy to the base of active groundwater, was recently named the Critical Zone because it supports life and is increasingly impacted by human actions. Understanding the complex interactions between processes that operate in and shape the Critical Zone requires interdisciplinary approaches that span wide spatial and temporal scales. Tectonic processes, weathering, fluid transport, and biological processes control the function and structure of the Critical Zone. Boulder Creek Critical Zone Observatory (CZO), one of three established by the National Science Foundation in 2007, is designed to explore the role of erosional history in the form and function of the Critical Zone. The headwaters of Boulder Creek can be divided into three distinct terrains: a glacially scoured landscape, a slowly eroding (possibly steady state) landscape, and a fluvially rejuvenated landscape. In these settings we plan to document differences in weathered profile development, model the geomorphic and weathering processes that have produced the landscapes, and monitor and model hydrologic, geochemical and ecological functioning. These cross-disciplinary studies are designed to integrate studies of process interactions up to the watershed scale. A further goal of the NSF CZO program, however, is to build the three independently conceived observatories into a network from which broader understanding - larger spatial scales but also deeper insight - can emerge.

22 Sep. Vasilii Petrenko, INSTAAR.
"Measurements of methane C-14 in Greenland ice: investigating methane sources during the last glacial termination."

We present the first measurements of 14C of methane (14CH4) in ancient glacial ice. 14CH4 should allow to unambiguously distinguish between wetland and fossil (clathrate or other geologic CH4) contributions to abrupt atmospheric CH4 increases observed at times of rapid warming in Greenland ice cores. 1000-kg-sized ice samples, dating to the Younger Dryas – Preboreal and Oldest Dryas – Bølling abrupt climatic transitions, were obtained from an ablation site in West Greenland. Measured 14CH4 values (28 – 35 pMC) were higher than predicted values under any scenario based on sample age. Sample 14CH4 appears to be elevated by in-situ CH4 production in the ice for some samples as well as by a second process that is likely direct cosmogenic production of 14CH4 molecules in the ice. 14C of CO and CO2 was measured to better understand these processes and corrections were applied to sample 14CH4. Although the corrected results have substantial uncertainties, they suggest that wetland sources were responsible for the majority of the Younger Dryas – Preboreal CH4 rise. The uncertainties in the corrected results for the OD-Bølling transition are too large to draw any conclusions about 14CH4 changes during that transition.

15 Sep. Jinho Ahn, Dept of Geosciences, Oregon State University.
"Atmospheric C02 and climate change on millennial to decadal time scales."

How atmospheric CO2 varies and is controlled on various time scales is an important question for understanding how the carbon cycle and climate change are linked. CO2 variations on glacial-interglacial cycles are relatively well studied, but variations on decadal to millennial scales are not. Here I show recent high-resolution ice core CO2 records that cover the last 90 ka. Phase relationships between CO2 and climates and several important mechanisms associated to the CO2 variations are discussed.

05 May Aslaug Geirsdottir, University of Iceland.
"A Holocene record of climate variation and soil erosion reconstructed from Haukadalsvatn, West Iceland."

Analysis of preserved physical and chemical proxies from lake Haukadalsvatn, West Iceland, provides compelling lines of evidence showing that severe soil erosion is a much older phenomenon in Iceland than from the Settlement as suggested by previous studies. In order to reconstruct the lake’s environmental evolution, two proxies, Biogenic silica (BSiO2) and Total Organic Carbon (TOC) have been analyzed. Both proxies should represent changes in primary productivity within the lake, however, TOC seems to provide two types of information: during stable times it is in harmony with the biogenic silica record and reflects bioactivity in the lake, but during unstable times it is in anti-phase with biogenic silica and records mostly aeolian input of old carbon into the lake driven by cold and windy climates.

28 Apr. Jason Janke, Department of Earth and Atmospheric Sciences, Metropolitan State College, Denver.
"Modeling permafrost distribution in the Front Range, Colorado."

Permafrost, or ground that remain below 0° C for two consecutive years, has been investigated using various field techniques, including excavations, Bottom Temperature of winter Snow (BTS), and geophysical methods. Such field methods are often expensive, time consuming, and are restricted in area. As a result, Geographic Information System (GIS) modeling techniques and Digital Elevational Model (DEM) variables related to permafrost occurrence (solar radiation, aspect, slope, and elevation) have been used to estimate permafrost distribution in the Alps. In the Front Range, field data are restricted in spatial extent, but rock glaciers are in abundance. Here, I present a probabilistic logistic regression model based on rock glacier topoclimatic information (elevation and aspect derived from USGS 10 m DEMs). The effectiveness of the model was evaluated by comparing mean probability scores with rock glacier activity, MAAT from climatic stations on Niwot Ridge, and BTS measurements. Permafrost scores greater than 50% covered about 12.0% (326.1 km²) of the study area (2,722 km²). Current modeled permafrost distribution showed a strong correlation with rock glacier activity classes, the – 1.0° C MAAT isotherm, and BTS measurements less than – 3.0° C, indicating that the model is adequately representing regional permafrost distribution. The model was also calibrated for cooler and warmer climates using a standard adiabatic rate for mountains (0.5° C per 100 m). In a 0.5° C cooler climate, permafrost could cover an additional 169.4 km², whereas in a 0.5° C warmer climate, 134.7 km² could be lost. These results may be extreme considering that permafrost will respond slowly to changes in climate.

21 Apr. Mark Williams, INSTAAR.
"Save our snow: Potential impacts of climate change on western U.S. ski areas for the years 2030, 2070 and 2100."

We evaluate how climate change resulting from increased greenhouse gas (GHG) emissions may affect snow coverage for two case studies: Aspen Mountain and Park City Mountain in the years 2030, 2070 and 2100. We evaluated climate changes using MAGICC/SCENGEN and the output from five General Circulation Models (GCMs) that best represent the western US. We bracketed potential climate changes by using the relatively low (B1), mid-range (A1B), and high (A1FI) GHG emissions scenarios projected by the IPCC. To obtain higher resolution climate change estimates, we spatially downscaled projections using a regional climate model (RCM, MM5), and a statistical downscaling model (SDSM).

The effects of climate change on snow coverage and depth were evaluated using the Snowmelt Runoff Model, a physically-based, temperature-index model. The model was calibrated using average snow conditions at both case studies, physical measurements of climate and snow properties by the respective ski patrols, and remote sensing images of snow covered area. After calibration, the snow model was run for 2030 and 2100 using output from the climate models.

By 2030, temperatures are estimated to increase 1.8 to 2.5 °C at Aspen Mountain and Park City Mountain, for all GCMs and emission scenarios. The length of the ski season is estimated to decrease by approximately 1 to 1.5 weeks at both ski areas, and the snowline is estimated at 2275 m. In 2100, temperatures are projected to increase 2.9 to 9.4 °C at Aspen Mountain and 4.2 to 8.9 °C at Park City Mountain. The snowline is estimated at 2800 to 2900 m at both ski areas for the A1B and B1 scenarios, and 3100 to 3200m for the A1FI scenario.

We also used a more comprehensive snow model to forecast changes in snow quality. The full energy-balance model SNTHERM was used to predict whether future snow quality will still be the high-quality champagne powder that we enjoy today or perhaps become Sierra cement. To run SNTHERM we needed daily predictions of important meteorological variables, such as net solar radiation, relative humidity, and wind speeds, that are not available from GCMs. A regional climate model was used for these projections; we'll discuss the pros and cons of using an RCM in this mode.

These same modeling scenarios can be used to inform future hydrologic conditions in snow-covered areas of the western US. For example, Brian and I used the modeling techniques above for Ken Strzepek's hydrologic modeling predictions of Boulder Creek that Ken presented last week.

CO-AUTHOR: Brian Lazar, Stratus Consulting Inc., Boulder, Colorado and American Institute of Avalanche Research and Education, Gunnison, Colorado.

KEYWORDS: climate change, snow, Aspen, Park City, ski areas, General Circulation Models, downscaling

14 Apr. Ken Strzepek, CEAE, CU-Boulder.
"Potential climate change impacts on Boulder Creek: Back to the future."

The talk will present results of a recent NOAA funded study of climate change impacts on Boulder's Water System. Stratus Consulting of Boulder lead the study with inputs from the City of Boulder, AMEC Consultants of Boulder and the University of Colorado.The talk will focus on how Boulder Creek responds to seasonal changes in precipitation and temperature using a hydrologic model developed for Boulder Creek. The model was then used to estimate the impacts of temperature and precipitation changes suggested by Global Climate Models for 2030 and 2070 using recent historical climate data. Finally using state of art research on paleo-hydrology (using tree-rings to reconstruct past streamflows and climates) we examine how Boulder Creek might have impacts over the past 400 years if the climate impacts of 2030 and 2070 had occurred is the past. From the looking in the past I will try to present some insights for the future.

31 Mar. Andrew Todd, Research Biologist, U.S. Geological Survey.
"Development of a zinc stable isotope technique to determine metal pathways and bioavailability to aquatic organisms."

Aquatic organisms are known to retain and accumulate dissolved heavy metals from their environment, with levels of uptake dependent on both exposure concentration and duration. In freshwater fish, the gill is widely considered to be the primary site of acute toxicity for many metals, and it has been proposed that accumulated metal can be used as an indicator of toxicity. The measurement of zinc accumulation on gill tissue is complicated by inherent difficulties in distinguishing between endogenous metals and metals accumulated during experimental exposures. The radioisotope 65Zn has been utilized in several studies as a tracer to quantify Zn kinetics at the gill; however, there are diverse factors limiting the widespread employment of this technique. This research utilizes commercially-available enriched stable isotopes of Zn as a promising alternative method for the quantitative evaluation of Zn uptake.

17 Mar. Malcolm Hughes, CIRES Visiting Fellow 2007-2008; Laboratory of Tree-Ring Research, University of Arizona,
"Confounded mystery in the mountains: the case of ancient pines."

Unusually wide tree-rings have been observed in recent decades in bristlecone pines from widespread locations at high elevations (3100 m.a.s.l. and above) near the upper forest border in the western USA. I present an enhanced and extended dataset from such environments. These wide rings are unique in the context of at least the last 3700 years. Sites at similar elevations, but further below the upper tree limit, do not show this increase. The implications of these observations for possible explanations of the growth increase will be discussed, in the context of environmental changes unique to recent times. These will include the possible effects of increasing atmospheric concentrations of carbon dioxide on the trees’ water use efficiency, enhanced nutrient availability related to pollution, shifts in seasonal climatic patterns, and mountain climate conditions unique to the 20th and 21st centuries. Particular attention will be given to this last explanation, and in particular to the possibility of uniquely “Anthropocene” patterns of vertical change and their consequences for tree growth.

The world's oceans, covering about 70% of the Earth's surface, play an important role in regulating the energy and gas exchange with the atmosphere. Large uncertainties exist in the description of the magnitude, and the oceanic and atmospheric controls of these processes. This deficiency is largely due to the difficulty in performing open ocean flux measurements. We have incorporated new advances in ship motion measurements and selective and fast response gas measurements and developed the first ship-borne ozone flux system. The principles and technical approaches for these flux measurements will be presented along with results from three recent research cruises. More information on this research is posted at
http://instaar.colorado.edu/outreach/ozone-oceans

25 Feb. Irina Overeem, INSTAAR & CSDMS, Community Surface Dynamics Modeling System
"Arctic Rivers; are they unique and are they changing?"

Arctic rivers are controlled by a number of processes that are specific to high-latitude and cold-climate regions. Important assumed river characteristics include 1) strong seasonality of river discharge due to a short melting season, 2) high sediment supply if basins are extensively glaciated, 3) lake outbursts and ice jams favoring extreme events and river flooding and 4) pulses of meltwater flooding the still frozen river mouth from a melting hinterland.

This talk discusses database analysis and modeling of basin characteristics, including topography, relief, basin wide temperature and precipitation, glacier extend and relative permafrost areas and presence and age of reservoirs and monthly discharge characteristics for 178 Arctic river basins. Model predictions of sediment discharge are validated against observed total loads for a subset of 38 rivers.

The Arctic basins indeed show strong seasonality; they on average drain 53% of their total water in just three months, as compared to 26% for all basins between 55 – 0°N. Seasonality strongly scales with both latitude and basin temperature. In contrast, monthly discharge variability has no significant trend with either latitude or basin temperature. Neither is there a significant relation between the ratio of glaciated area over total basin area of high latitude basins and their mean annual load. This is explained partly by the fact that the importance of glaciers, which theoretically would supply high sediment loads, scales with river drainage basin area. Relatively small basins have larger glaciated areas proportionally. These small basins are also most impacted by extreme discharge events, e.g. frequent lake outbursts due, whereas the effects of these local events are dampened in the largest Arctic basins. On the other hand, early melting in the hinterland and river discharge draining into a still frozen deltaic region is unique to the much larger basins that stretch into lower latitudes. This effect is evident in most of the 10 largest Arctic river basins.

Our data corroborates that climatic warming over the last century coincides with an Arctic-wide increase in total annual river discharge. Remarkably though, seasonality of the discharge and similarly of modeled sediment loads, generally decreased over the last decade, partly due to construction of dams, but likely due to changing seasonal precipitation. We aim to better understand the scaling relations to reliably assess seasonal circum-arctic river sediment loads to the coast.

19 Feb. Jim White, U. of Colorado at Boulder
"Past climate and modern greenhouse gases: research directions in INSTAAR's Stable Isotope Lab"
Note Special Location and Event: Candidate for new INSTAAR Director.
Tuesday 4:00 pm - 5:00 pm, Benson Earth Sciences room 380
30 minute reception before the talk

INSTAAR's Stable Isotope Lab is involved in two new deep ice cores as well as new research on the modern carbon cycle. This talk will describe the thesis research projects of four SIL graduate students. Samantha Stevenson from ATOC will focus on the signal of ENSO recorded in the new WAIS deep ice core in West Antarctica and how ENSO evolved over the past 20,000 years. Tyler Jones in ENVS will be studying the new NEEM ice core from Greenland, with a focus on the last interglacial period and how that period can inform us about our future climate. Caroline Alden in GEOL will be using carbon isotopes in atmospheric carbon dioxide to better understand how the ocean and terrestrial biosphere are changing their uptake of excess carbon dioxide from fossil fuel burning. And Candice Evans is assessing problems with the analyses of oxygen isotopes of carbon dioxide made on NOAA flasks, with the goal of better constraining variability in the global to regional scale balance of photosynthesis and respiration.

15 Feb. Jonathan Overpeck, U. of Arizona
"Climate change, sea level, and western drought: Dangerous anthropogenic interference?"
Note Special Location and Event: Candidate for new INSTAAR Director.
Friday Noon - 1:00 pm, Benson Earth Sciences room 380
Followed by lunch with geology faculty 1:00-2:00pm

The reality of global warming, reflected in a broad spectrum of climate system change, is now unequivocal. Moreover, human complicity in global warming has also been established beyond a reasonable doubt. With these and other advances embodied in the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4) has come a shift in scientific focus toward efforts designed to improve our understanding of what will happen in the future, and to what can be done to deal with the reality of global to regional climate change. Major efforts are now needed to develop strategies for adapting to climate change that is already in the pipeline, and also to identify climate changes that may be deemed unacceptable, and thus worthy drivers of mitigation strategies designed to reduce the rate of atmospheric greenhouse gas increases to “safe” levels.

There may be many aspects of future global climate change that will ultimately be deemed undesirable and worthy of mitigation efforts, but two major issues are already coming into focus. The first is global sea level rise coupled with increasing tropical storm intensities. There is no doubt that global sea level is rising, and little doubt that the rates of sea level rise are likely to increase. In contrast to what some biased media and individuals are saying, the IPCC AR4 did not lower estimates of future sea level rise. Indeed, the most recent estimates suggest that 1m or more of sea level rise could occur by 2100, as well as a commitment to a much larger sea level rise over subsequent centuries. The wildcard will be the future behavior of the large polar ice sheets, and there is growing evidence that the ice sheets are more vulnerable to global warming than widely thought.

Although coastal areas could thus be big losers in the face of continued climate change, recent climate change coupled with climate change projections indicate that the American West – including the alpine West - could be a more near-term casualty. Surface air temperatures are already rising faster than elsewhere in the coterminous United States, and will likely continue to rise steadily. These temperature increases are already causing snow to fall increasingly as rain, and also to melt earlier in the year. Thus, even in the absence of a precipitation decrease, there will be less snow-related run-off and related surface water flow. This trend is also being exacerbated in some parts of the West by human-caused increases in atmospheric dust loading. Unfortunately, nearly all state-of-the-art climate models being forced with increasing greenhouse gases (and other human-caused pollution) are also simulating a steady decline in average wintertime precipitation in the Southwest. More troubling is the fact that these simulated changes are also in accord with what has been happening in the real world – there is a growing scientific consensus that winters will become much hotter and significantly drier due to the greenhouse-gas climate forcing. On top of these trends in average condition is the likelihood that multi-year, even multi-decade, drought will also become more common. Thus, the recent western drought – already the worst of the instrumental era – could be a harbinger of greater aridity to come, and also a significant threat to the West as we know it. Fortunately, there are solutions if we choose to act aggressively.

06 Feb. Bill Curry, Woods Hole Oceanographic Institution
"The Atlantic Ocean deep circulation 21,000 years ago"
Note Special Location and Event: Candidate for new INSTAAR Director.
Wednesday 4:00 pm - 5:00 pm, Benson Earth Sciences room 380
30 minute reception before the talk

Our understanding of past changes in ocean circulation comes from tracer chemistry in fossil benthic foraminifera, which provide the means to reconstruct past deep water mass circulation patterns. The most complete synthesis of past circulation is for the last glacial maximum (LGM 21,000 years ago). The chemical gradients recorded in LGM foraminifera document a shoaling of North Atlantic Deep Water (NADW, the principal northern-source water mass) compared to today. NADW was replaced with a much larger volume of Antarctic Bottom Water, which can be traced as far north as 60 N. These water masses experienced large changes in salinity, an indication that the changes in ocean circulation were linked to large scale changes in the hydrological cycle during the glacial period. Although the rate of deep water production in the North Atlantic may have been reduced, large bathymetric gradients in ocean chemistry require that advection remained strong enough to overcome strong vertical mixing in the deep Atlantic.

28 Jan. Larry Benson, USGS.
"The rise and fall of the midwestern Cahokians and the southwestern Anasazi."

Both the Missippian Cahokians and the Anasazi though physically separated by 1500 km experienced nearly simultaneous changes in population density. Between about AD 1025 and 1130 populations surged in both regions only to be followed by rapid declines. In the Southwest, most of the Anasazi great houses in the San Juan Basin were abandoned by AD 1150 as was the large Richland farming complex in the Illinois uplands adjacent to Cahokia. New tree-reconstructions of the Palmer Drought Severity Index by Ed Cook and others provide the substance for a hypothesis that explains the near-simulataneous rise and fall of these distant cultures. In particular, the megadrought of the mid-12th century appears to have stressed the principal food supply (maize) of both cultures with the late 13th-century drought providing the final blow.

25 Jan. Matt Sturm, USA-CRREL-Alaska
"White on green: Snow, shrubs, and the changing climate of the Arctic"
Note Special Location and Event: Candidate for new INSTAAR Director.
Friday 12:45 pm - 1:45 pm, Benson Earth Sciences room 380
30 minute reception before the talk

At least 9 million km2 of the terrestrial Arctic (excluding Greenland) are covered by tundra, of which a major component is shrubs. We know from plot, photographic, and remote sensing evidence that these shrubs are increasing in size and areal coverage, most likely due to a change in climate. A key part of the arctic climate system is the snow cover, which blankets the region for 8 to 10 months of the year. Snow is also an essential element of the tundra ecosystem, both acting upon, and being acted on, by the shrubs. But the snow cover, too, is changing, melting away in Spring on average 2 to 3 weeks earlier than 30 years ago. A number of recent studies suggest that snow-shrub interactions, or more broadly, snow-vegetation interactions, are helping to push the Arctic down a trajectory of change through a set of positive feedback mechanisms that could have global implications. These feedbacks range from alterations in the land surface albedo to changes in species composition and active layer depth. Small things like soil microbes, snow crystals, wind-blown snow and shrubs, may be leading actors in a climate change drama whose outcome is of concern to us all.

07 Apr. Jan Harff, Baltic Sea Research Institute, Warnemunde.
"Expedition to Western Greenland Shelf and Fjords, June-July, 2007, within the frame of the IPYs."

The objectives of the R/V “Maria S. Merian” expedition were the investigation of the interrelation between hydrosphere, geosphere, and climate in the western Greenland coastal waters and the impact to environmental change during the Late Quaternary. An international team of geologists, geophysicists, geodesists, and paleo- oceanographers contributed to three topics by interdisciplinary studies along of transects from the roots of three fjords to the shelf edge: (1.) Reconstruction of climate and ice dynamics in western Greenland during the late Pleistocene and Holocene. (2.) Influence of climate change and anthropogenic factors on biogeochemical cycles during the Holocene. (3.) Glacio-isostatic deformation of the earth crust and its influence on coastal processes.

The measuring program including hydrographic survey, geophysical profiling, sedimentological sampling and geodetical measurements focused on east-west profiles running from inner fjords to the shelf edge that will reflect the north-south gradient of the parameters to be measured between 64° and 72° N. The map shows the route of the expedition and the four areas: A: Nordre Strømfjord B: Disko Bay C: Vaigat and Uummannaq Fjord D: Nuuk Fjord

The following are some first results:

1. The geodetical network for measurements of glacio-isostatic adjustment in Western Greenland has been completed. It is possible now to measure vertical dislocations of the earth’s crust in Western Greenland for model parametrization and comparison with the Baltic coast.

2. Sediment cores have been sampled from the West Greenland shelf. Geochemical and sediment-physical parameters have been measured on board. These data form the first data records describing the history of Holocene climate and the Western Greenland current with high resolution.

3. The technical equipment of the “Maria S. Merian” did allow sampling of sediments within the ice-fjords. These cores describe the climatically controlled ice-dynamics of the feeding glaciers.

4. The sea floor close to the mouth of the ice-fjords and along the iceberg drift tracks has been mapped using a multibeam echosounder. Ploughmarks show different drift directions of icebergs pointing at variations of transporting marine currents.

5. Traces of anthropogenic impact have been identified through geochemical proxies within sediments of the Qaumarujuk Fjord. Here, the lead/zink mining closed to Maarmorilik in the 1970s had lead to significant impact on the aquatic ecosystem.

In Uummannaq the participants of the expeditions met with local school teachers, students and citizens of the Uummannaq commune and discussed targets and outcomes of the expedition particularly with regard to climate change.

03 Dec. Tom Stoffel, National Renewable Energy Laboratory NREL.
"Solar radiation measurements & modeling for renewable energy and climate change research"

Understanding the interactions of solar energy with the earth-atmosphere-ocean system requires accurate measurements of solar irradiance. Following an overview of the types and functions of various broadband radiometers, I will describe a satellite-remote sensing approach to producing hourly solar resource data. Next, I will summarize the recently released National Solar Radiation Database and present a few Geographic Information System (GIS) analyses based on the new resource data. Other renewable energy related topics will include spectral irradiance measurements and modeling with applications to photovoltaic and concentrating solar power technologies, and current research in surface solar irradiance forecasting to meet the anticipated needs of the electric utilities. A brief description of the instrumentation used to meet the goals of the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Program will conclude my presentation.

26 Nov. Patrick Bourgeron, INSTAAR.
"Interactions between landscapes and humans in the Colorado Front Range since the 19th Century: Resilience and regime shifts in coupled natural and human systems"

Interactions between environmental and socio-economic dynamics in the Colorado Front Range have generated current landscape mosaics. Here, we examine the effects of these interactions on patterns of changes and ecological resilience across the urban-wildland/rural interface and address four general questions: (1) What are the mechanisms by which environmental and socio-economic dynamics interact to affect changes in the urban-wildland/rural interface? (2) What are the mechanisms by which environmental and socio-economic attributes contribute to the resilience of the coupled natural and human systems? (3) What conditions contribute to the loss of resilience in the study area? (4) What are the consequences of such loss of resilience for these areas? Results to date indicate that since 1860 there have been three major shifts in the structure and function of regional ecosystems in response to changes in climate variability, population increase, changing land use, and fire suppression. Extreme droughts have combined with fuel loading increase (due to fire suppression) and land cover change (a function of land use change, such as exurban development) to alter landscape patterns and stand structure. Changes in landscape patterns and stand structure in turn create a positive feedback to fuel loading accumulation and therefore likely influence the threshold behavior of fire intensity and size. Changes in disturbance regimes alter the dynamic linkages between ecosystem structure and function, resulting in progressive changes in the Colorado Front Range stability landscape as well as a steady erosion of ecological resilience, defined as the ability of landscape configuration to contain fire spread.

12 Nov. Natalie Mladenov, INSTAAR.
"Controls on dissolved organic matter in high elevation lakes of the Sierra
Nevada Mountains, Spain"

Through the EcoSensor network (www.ecosensor.og), high elevation and remote lakes have been selected to evaluate the biogeochemical and microbiological impacts of global change, specifically the effects of increasing atmospheric aerosols derived from arid soils. This presentation will provide an overview to ongoing EcoSensor research with specific focus on dissolved organic matter dynamics in high elevation lakes of the Sierra Nevada Mountains, Spain. Alpine lakes of the Sierra Nevada are above treeline, low in dissolved organic carbon (DOC), and subject to high incident UV radiation. Due to their high elevation (around 3000 masl) and proximity to the Sahara Desert, Sierra Nevada lakes also represent ideal sites for detecting the biogeochemical impacts of dust deposition.

A 3 year study was performed to evaluate the controls on DOC concentrations and DOM optical properties in two contrasting Sierra Nevada lakes, located approximately 3 km apart. In the deeper, unvegetated, precipitation-fed lake, DOC concentrations and UV-vis absorbance were strongly influenced by dust deposition events originating in the Sahara and Sahel regions of Africa. DOC concentrations and DOM optical properties in the shallower lake surrounded by meadows showed a weaker signal from dust deposition and were influenced to a greater degree by evaporation.

The organic fraction of atmospheric aerosols is only beginning to be characterized and better understood. These results highlight the important role of dust deposition as a DOM source. A further finding of inconsistent or absent relationships between UV-vis absorbance and DOC concentrations in these lakes suggests that established patterns between absorbance and DOC concentrations do not hold in these low DOC, high alpine aquatic ecosystems.

05 Nov. Bob Stallard, INSTAAR.
"The Agua Salud Project - Water, carbon, and ecosystem services"

The Agua Salud Project utilizes the Panama Canals central role in world commerce to focus global attention on the ecosystem services provided by tropical forests. It will be the largest field experiment of its kind in the tropics aimed at quantifying the environmental services (water, carbon, and biodiversity) provided by tropical forests. The Agua Salud [healthy water] Basin is our principal field site. This watershed and the headwaters of several adjacent rivers include both protected mature forests and a wide variety of land uses that are typical of rural Panama. Experiments at the scale of entire catchments will permit complete water and carbon inventories and exchanges for different landscape uses. To this end, we have now purchased 500 ha of degraded land next to the Soberania National Park, which is intact forest. In adjacent lands that we have not purchased, landowners will be funded to maintain land uses and provide security. The following questions will be addressed: (1) How do landscape treatments and management approaches affect ecosystem services such as carbon storage, water quality and quantity, dry-season water supply, and biodiversity? (2) Can management techniques be designed to optimize forest production along with ecosystem services during reforestation? (3) Do different tree planting treatments and landscape management approaches influence groundwater storage, which is thought to be critical to maintaining dry-season flow, thus insuring the full operation of the Canal during periods of reduced rainfall and severe climatic events such El Niqo. In addition we anticipate expanding this project to address biodiversity, social, and economic values of these forests.

22 Oct. Caspar Ammann, NCAR.
"Understanding natural climate variability: The key to climate change."

By mid-September 2007 sea-ice coverage of the Arctic Ocean reached the smallest extent since record keeping. This message was just the latest in an ever-increasing number of signals that the climate is changing and that the globe is warming up. But how can we be so sure that this recent trend is man-made and not just an artifact from a too short instrumental record and that other factors, such as internal variability or changes in solar activity, might be responsible for what is happening right now? Just how do these and possible future anthropogenic signals actually measure up against the range of natural variations? Clean separation of anthropogenic from natural climate change is not always easy. Process studies as well as the time-perspective gained from past climates allow for a better understanding of the ongoing change, and the respective roles of natural and human contributions can be assessed.

This presentation will focus on the available data that strongly supports the notion of human induced climate change and where climate science is currently heading to improve projections of relevant issues. Results of high-resolution climate reconstructions as well as state-of-the-art climate models indicate that natural forcing factors have dominated climate before the 20th century. Increased emissions of greenhouse gases are, however, responsible for the current rapid warming. If emissions are not reduced in the near future, then the Earth's climate system will undoubtedly experience drastic changes that far exceed the range of what civilizations have experienced. But simulations also show that strong reductions of emissions can keep climate changes in check.

15 Oct. Miriam Duhnforth, INSTAAR.
"Constraints on the timing, pattern, and mechanisms of sediment export from catchments in the eastern Sierra Nevada, CA"

Sediment fans record the history of sediment evacuation from their adjacent catchments. A close linkage between both catchment and fan allows the reconstruction of the integrated effect of sediment production, storage, and sediment transfer to the fan in space and time. These processes are mainly controlled by external boundary conditions such as climate or tectonics, but the lack of absolute age control on sediment deposition, unconstrained tectonic boundary conditions, and poor understanding of catchment dynamics often limit our ability to decipher their relative importance. This study demonstrates how the internal morphology of two catchments in the eastern Sierra Nevada, CA, one glacially modified and the other without glacial modification, controls the fan surface morphology and the pattern of the debris-flow chronology.
Based on cosmogenic 10Be dating of debris-flow boulders and topographic analysis of the fan surface and catchment geomorphology, the results suggest that (a) although debris-flow deposition occurs throughout glacial-interglacial periods, deposition seems to be enhanced during glacial periods, (b) observed variations in the depth of fan-head incision lead to differences in the length of the preserved depositional record, and (c) variations in the incision depth are promoted by the potential for sediment trapping in the catchments through glacial modification of the valley floor. From these findings we infer that local variations in climate, as seen by differences in the degree of glaciation in alpine catchments, can significantly modify the pattern of sediment export to a fan and the resulting fan surface morphology and chronology.

08 Oct. Rob Fatland, VEXCEL.
"Results from SEAMONSTER, a smart sensor web in Southeast Alaska."

The University of Alaska Southeast and Vexcel-Microsoft have partnered under NASA sponsorship to develop a smart sensor web in Southeast Alaska with multiple purposes: Acquire hydrological, glaciological, and other environmental data, support other researcher projects by means of a wireless infrastructure, enable educational learning, advance environmental real-time monitoring and data publication by such means as OGC-compliant web services and virtual globes (Virtual Earth, Google Earth), create online documentation of the project and address important questions about the biogeochemistry of semi-glaciated watersheds. The "year one" progress and results will be described across these objectives with further remarks on future direction, including a planned implementation local to Boulder and potential use of this work in earth science education.

01 Oct. Wes LeMasurier, INSTAAR.
"Neogene tectonic events in the Marie Byrd Land Sector of the West Antarctic Rift System: Their potential impact on ice sheet evolution and stability."

The West Antarctic rift system is buried beneath 1-4 km of ice over much of its extent, obscuring vast areas that could provide clues about the potential for active volcanism beneath the ice sheet, and whether significant tectonic movement has taken place in Cenozoic time. This study explores the consequences of viewing the ice as basin fill, and of approximating the mass equivalent of ice as unconsolidated sediment. It then compares the results with active rift systems elsewhere in the world. The results suggest (1) that the interior rift trough is relatively cool, and the potential there for destabilizing subglacial eruptions is low, (2) that extension and over-deepening of interior basins, like the Bentley Subglacial Trench, have taken place beneath the ice sheet in Neogene time, and (3) that dome uplift and the growth of large volcanoes along the Marie Byrd Land coast, together with the subsidence of interior basins, have greatly increased the topographic relief of the rift system in Neogene time. Recent studies suggest that West Antarctic glaciation first appeared during the Oligocene. The implication of this study is that the Oligocene ice sheet originated on a low relief landscape near sea level, adjacent to a much shallower inland sea, and has since evolved in an environment of progressive basin deepening, dome uplift, and volcanism, unlike that of any other ice sheet in the recent past.

24 Sep. John Milliman, Virginia Institute of Marine Science, William & Mary.
"Climatic and anthropogenic roles in changing river discharge to the global ocean."

During the last half of the 20th century, global precipitation and cumulative water discharge from 135 representative rivers (watershed areas ranging from 0.3 to 6300 x 103 km^2) to the global ocean remained constant, although discharge from ~40% of these rivers changed by 30%. Runoff trends in many rivers reflected primarily changes in precipitation, few experiencing significant changes in either parameter. Collective runoff from many mid-latitude rivers, in contrast, decreased by ~60%, in large part due to damming and irrigation. A number of high-latitude and high-altitude rivers experienced increased runoff despite generally declining precipitation. Poorly constrained precipitation data do not seem to explain fully these "excess" rivers; changed seasonality in runoff, decreased storage and/or decreased evapotranspiration may also play important roles.

This talk is based on a paper that will be submitted to Geophysical Research Letters shortly. The authors are John D. Milliman, K. L. Farnsworth, L. C. Smith, P. D. Jones and K. H. Xu

17 Sep. Tad Pfeffer, INSTAAR.
"Glaciers dominate eustatic sea-level rise in the 21st Century."

Ice loss to the sea currently accounts for virtually all of sea-level rise not attributable to ocean warming; about 60% of the ice loss is from glaciers and ice caps rather than from the two ice sheets. The contribution of these smaller glaciers has accelerated over the last decade, in part due to dramatic thinning and retreat of marine-terminating glaciers associated with a dynamic instability generally not considered in mass balance/climate modeling. This acceleration of glacier melt may cause 0.1-0.25 m of additional sea-level rise by 2100.

This talk is based on a paper that appeared in both the online and print editions of Science magazine (July 19th and August 24th, 2007, respectively). Authors were Mark F. Meier, Mark B. Dyurgerov, Ursula K. Rick, Shad O'Neel, W. Tad Pfeffer, Robert S. Anderson, Suzanne P. Anderson, and Andre F. Glazovsky.

10 Sep. Leanne Lestak, INSTAAR.
"GIS-based measurement of coastal change in the southeast Chukchi Sea, Alaska."

Coastal environments at high latitudes are experiencing rapid change. Coastal erosion threatens a variety of nearshore marine, terrestrial, and freshwater habitats, and may be accelerating with Arctic warming. To better understand impacts for national parks in northwestern Alaska, a collaborative study has begun to document coastal change in the southeast Chukchi Sea. The comprehensive geospatial study includes: creation of a high-resolution (0.6 m) orthophoto mosaic for 2003; rectification of historic aerial photography from ca. 1950 and ca. 1980; and quantitative analysis of coastline and bluff erosion. For Bering Land Bridge NP and Cape Krusenstern NM, the GIS analyses quantify complex spatial and temporal variability tied to environmental forcing, as well as a dynamic range of coastal morphologies and processes. The geospatial analysis documents that most of the ca. 400-km-long coast from Wales to Kivalina has experienced erosion in the past five decades, with long-term average rates of 0-3 m/yr. Direct impacts include beach and bluff retreat, overwash deposition, migration or closure of inlets and lagoons, capture of thaw-lake basins, and release of sediment and organic carbon to nearshore waters (see Figs. 1-3). Observations of shrub expansion and thermokarst degradation are also consistent with rapid change. Coastal ecosystems in the region appear to be sensitive to the frequency and intensity of storm events, increasing temperatures, permafrost melting, sea-level rise, and increasing length of the summer ice-free season.

This talk is based on an in press paper by Manley, William F., Lestak, Leanne R., Sanzone, Diane M., Jordan, James W., Mason, Owen K., and Parrish, Eric G.

Special Seminar
18 Jun. Jinho Ahn, Department of Geoscience, Orgegon State University.
"Atmospheric CO2 and climate change on millennial time scale during the last glacial period."

How atmospheric CO2 varied during Dansgaard-Oeschger (D-O) and Heinrich (H) events is an important question for understanding how the carbon cycle and climate change are linked. In order to answer to this question, we need common time scales for climate proxies and atmospheric CO2 [Stauffer et al., 1998]. Previous studies of the 17-47 ka section of the Antarctic Bryd ice core showed that atmospheric CO2 appeared to rise at about the same time as Heinrich events H4-H5 [Stauffer et al.,1998] although the precision of these previous CO2 data was not sufficient for precise comparison with Greenland ice core records. High-quality CO2 records from the Taylor Dome ice core show atmospheric CO2 variation of ~ 20 ppm during the period from ~ 60 to 20 ka. However, the relative timing of the CO2 variations from Taylor Dome and Greenland temperature is not well constrained [Indermühle et al., 2000].

Here we provide atmospheric CO2 records from ~90 to 30 ka BP (thousand years before 1950) on a chronology synchronized with Greenland ice core records, allowing direct comparison of CO2 with Greenlandic [Grootes et al., 1993] and Antarctic [Johnsen et al., 1972] temperature proxies, Heinrich events [Rashid et al., 2003; Sarnthein et al., 2001] and atmospheric CH4 [Blunier and Brook, 2001].

Atmospheric CO2 rose several thousand years before abrupt warming in Greenland associated with Dansgaard-Oeschger events, 8, 12, 14, 17, 19, 20, 21, large warm events. The CO2 rise terminated at the onset of Greenland warming for each of these events, implying a global mechanism that can simultaneously affect atmospheric CO2 and temperature in both hemispheres. Also, the start of CO2 increases predates massive ice discharge events (H events 4, 5, 5a, 6) by 0 ~ 3 ka. Atmospheric CO2 is strongly correlated with the Antarctic isotopic temperature proxy with an average time lag of 720 ± 370 yr (mean ± 1ˆ) during 65 ~ 30 ka. Several important mechanisms associated to the CO2 variations are discussed. The new data and chronology should provide a better target for models attempting to explain CO2 variability and abrupt climate change.

30 Apr. L.W. Morland, School of Mathematics, University of East Anglia.
"Steady radial ice sheet flow with fabric evolution."

A fabric evolution model is described, based on crystal rotation and consequent induced anisotropy as main glide planes are no longer randomly distributed. The conventional reduced model for ice sheet flow, exploiting the very small aspect ratio, or equivalently a scaled dimensionless viscosity, is extended to incorporate the fabric evolution, for which the evolving deformation of each ice element must be determined during its flow through the sheet. Steady radial flow with a prescribed temperature field is adopted to illustrate the effects of the fabric compared to the conventional isotropic viscous fluid model. These are significant.

Contemporary dust emission within North America is volumetrically minor on a global scale, but it is, nevertheless, important for many reasons: ecosystem health (loss of soil nutrients via wind erosion with gains elsewhere); visibility reduction (bearing on protected air quality and transportation hazards); and human health.

Our investigations to elucidate the conditions that promote or suppress dust emission in American drylands focus on interactions among geologic processes, climate, vegetation dynamics, hydrology, and human activities.

Current studies of global dust center on its climatic effects. Future work will be increasingly driven by concerns about the connections among desertification, dust, human health, and poverty. North American dust sources provide nearby test sites for developing new methods to understand and monitor dust emission as well as to assess associated health risks.

16 Apr. Michael Gooseff , Colorado School of Mines.
"Increased hillslope thermokarst activity in the Brooks Range of Alaska, - implications for aquatic ecosystems."

Permafrost thaw dynamics have generally been well characterized near thaw lakes or lake margins (particularly thermokarst lakes). In the past 4 years, we have been documenting permafrost thaw that is resulting in landslide-type failure features across the Brooks Range and the Northern Foothills. These failures produce increased amounts of sediment and enhanced nutrient fluxes to receiving waters. Our current analysis suggests that the frequency and distribution of hillslope thermokarsts is on the rise, likely as a response to a warming climate in the Arctic. Thus we are exploring how to 1) characterize and predict the current and future distributions of these features, and 2) determine the potential impacts of increased sediments and nutrients to Arctic stream networks.

09 Apr. R. Steven Nerem, NCAR.
"Satellite measurements of sea level change."

Over the last few decades, satellite geodetic measurements together with in situ measurements, have revolutionized our understanding of present-day sea level change. With measurements from satellite altimeter missions and satellite gravity missions, we are now able to start answering some important questions with regards to global sea level change and its regional variations. What have we learned from these measurements? Would we change any of the decisions we made in the past? What are the remaining questions to be answered? What suite of measurements are needed to answer these questions? The record of sea level change from satellite altimetry will be reviewed, its error sources and limitations discussed, and the results placed in context with other estimates of sea level change from tide gauges, in situ measurements, and global climate models. The much shorter, but just as important, record of ocean mass variations from satellite gravity measurements will be similarly reviewed. Finally, the need for continuing the satellite measurements of sea level change, and possibly developing new measurements, will be discussed in the context of future missions and the scientific gain that would result.

02 Apr. Douglas S. Robertson, CU-Boulder Dept of Geological Sciences and CIRES.
"Survival in the first hours of the Cenozoic."

The extinction of dinosaurs is one of the major puzzles in paleontology. Recent modeling provides convincing evidence that all the latest dinosaurs were killed off within a few hours of the Chicxulub impact. For several hours following the impact the entire Earth was bathed with intense infrared radiation from ballistically reentering ejecta. The global heat pulse would have killed unsheltered organisms directly and ignited fires at places where adequate fuel was available. Sheltering underground, within natural cavities, or in water would have been a necessary but not always sufficient condition for survival. Survival through sheltering from an initial thermal pulse is not adequately considered in literature about Cretaceous- Tertiary nonmarine extinctions. This talk will compare predicted intense, short-term, thermal effects with what is known about the fossil record of nonmarine vertebrates and suggest that paleontological evidence of survival is compatible with theoretical results from bolide physics.

19 Mar. Robert S. Anderson, INSTAAR.
"Glaciers and their impact on landscapes: from the highest peaks to the deepest fjords."

I will summarize our recent work on glacial landscapes, and advertise where we view the frontier to be in this field. I first synthesize our work on Alaskan glaciers, where we attempt to extract a better understanding of glacial sliding. I then discuss how we model glaciers in 1D and 2D, and glacial valley evolution on long time scales. I end by turning to the future, and lay out the problems of modeling the evolution of very high mountains, and the insertion of fjords into continental edges.

Understanding the evolution of glacial landscapes requires a knowledge of how temperate glaciers work. This has taken us to two Alaskan glaciers. In particular we must understand glacial sliding, as it is sliding that erodes a glacial bed. In our work on the small 7x1 km Bench Glacier in Alaska we used a series of GPS monuments and simultaneous documentation of the water balance on the glacier to document a sliding history that is intimately tied to an evolving hydrologic system within the glacier. On the Kennicott Glacier, near McCarthy Alaska, this last summer’s research revealed the sliding history on this much larger glacier. We targeted the glacial sliding response to the annual outburst flood from Hidden Creek Lake as a natural experiment. The response was indeed a strong one, as the glacier sped up by at least 6-fold during the passage of the floodwave. In all of these field cases, sliding occurs as a response to inputs of water that exceed the capacity of the glacial plumbing system.

Glacial models require both meteorological inputs and glacial dynamics. The LGM glaciers of the Kings canyon and Yosemite areas of the Sierras serve as tests of meteorological models, as the glaciers lived on both the windward and lee of this strong orographic barrier. Our most recent 2D simulations can match simultaneously the terminal moraines of many glaciers draining major ice caps along the Sierran crest. Models of glacial erosion of valleys produce flattening of valley floors, steepening of headwalls, steps in trunk valleys and hanging of tributary valleys.

We have embarked on two new projects. In the first, we explore the roles of lithology in glacial landscapes, and target the highest topography in North America. Mt. Denali rises several thousand meters above the surrounding terrain, in part because it is caught up in a bend in the Denali right lateral fault, but importantly because it is also composed of a granitic pluton that is very difficult to erode. I will briefly outline the lines of evidence we will attempt to collect to explore this issue. In the second project, we are addressing the insertion of fjords into the continental margins. Fjords serve as tap points into large ice sheets; the outlet glaciers that drain through them deliver many 10s of percent of the ice to the ocean. They did not exist at the beginning of the Plio-Pleistocene glacial cycle in the northern hemisphere. I will present our models of fjord insertion, and introduce how we will attempt to document the timing of the fjord insertion using the major fjords of eastern Baffin Island as our field site.

12 Mar. Barry Smith, British Geological Survey.
"Integrating soils and geology – The Sustainable Soils Programme of the British Geological Survey."

Soils and their interface with superficial geological materials form a boundary layer between the atmosphere and geosphere that constitutes a unique, finite (on human timescales) veneer that supports a significant proportion of life on earth. However, despite their importance little attention has been given to the protection of soils and their long-term development and function. This coupled with direct and indirect threats to soil systems from climate change and continued degradation resulting from mans activities, has resulted in the development of legislation which highlights, not only the importance of soil but also a need to better understand the sustainability of processes coupling the whole near surface environment to the atmosphere, hydrosphere and geosphere.

In April of 2005 the BGS embarked on a five year programme of activities aimed at providing better geological information and support to environmental scientists wishing to understand the Earths near surface environment in a more integrated manner. This presentation describes the main activities of the programme to data covering the mapping and classification of soil parent materials, spatial modelling and geophysical characterisation of the soil-geology continuum and the study of geology-soil interfaces and how properties change across them.

The fragmentary and disarticulated remains of an adult male who died in his early 20’s have been excavated from On Your Knees Cave, an archeological and paleontological site on Prince of Wales Island, Southeast, Alaska. The human bone has been 14C dated to circa 9,800 BP. They are oldest dated human remains known from Alaska and Canada. δ13C and δ15N values demonstrate the individual’s diet was based primarily on marine foods and the 14C age should be adjusted to c 9,200 based on the regional marine carbon reservoir extrapolated from the near-by Queen Charlotte Islands. Stone tools from the site include microblades, bifaces, flake cores, and other tools. Trace element analysis documents a least two sources for the obsidian from which some of the tools were made, Mount Edziza on the British Columbia mainland and Suemez Island in Southeast Alaska. These data suggest that by c 9,200 14C BP (10,300 CYA) humans along the Northwest Coast of North America were coastal navigators with an economy based on maritime subsistence and established trade networks, or travel routes, between islands and the mainland for obsidian. DNA analysis identify this individual as belong to haplogroup Q-M3, a subgroup of haplogroup D, which may suggest this individual is the descendant of a very early population that may have colonized the west coast of the Americas during the late Pleistocene. This research program has also been a model of cooperation between Native people, federal resource managers, and research scientists during a time when the excavation of ancient human remains has often be contentious and adversarial.

26 Feb. Alex Blum , USGS.
"Weathering of glacial moraines in the French Alps."

Samples of recent glacial sediments and 9 soil profiles ranging in age from 360 years to ~300Ky were collected from near Chamonix toward Lyon. The mineralogy of the <2 mm size fraction of each soil as a function of depth was analyzed by quantitative XRD. Soil profiles 17 Kyr and younger were derived almost exclusively from crystalline rocks. Older moraines also contained significant limestone and dolomite.
The 360 yr moraine has a well developed organic horizon, suggesting the high availability of nutrients in the till, but no clear indication of silicate weathering. Within the ~10 Ky till, chlorite (formed by retrograde alteration of biotite) was weathered to smectite in the upper ~20 cm, but there is no major change in plagioclase or other primary silicate concentrations or kaolinite formation. The ~17 Ky till showed plagioclase weathered in the top 15 cm, and an incipient A horizon. The older tills (>100 Ky, and closer to Lyon) all have well developed A and B horizons, with the B horizon depth increasing with the till age from ~65 to ~150 cm. Weathering of plagioclase and K-feldspar in the soil horizons increases with age, as does the development of an argillic kaolinite horizon. Carbonates in the A and B horizons are severely depleted, but abruptly reach concentrations near that of the unaltered till at the base of the B horizon, the same depth at which silicate weathering appears to cease.
The mineralogy of some <2 μm fractions were also analyzed. Suspended stream sediment and till from modern glaciers has mineral compositions of the <2 μm fraction that are nearly identical to the bulk tills and bedrock. Alteration of the <2 μm fraction of older tills is similar to the <2 mm fraction, with feldspar weathering above the base of the B horizon, but little alteration below. This suggests that the high surface area of the primary silicates in the clay-size fraction of till played a subordinate role in controlling the rate of chemical weathering, and weathering models with a large dependence on mineral surface area may not describe the weathering behavior of this chronosequence. Rather, other factors such as the evolution of solution chemistry may have a major control on weathering rates.

19 Feb. Peter Barrett, Antarctic Research Centre, Victoria University of Wellington.
"Antarctic climate history - deep past and near future."

Antarctica has occupied its present polar position for over 100 million years and for most of that time it was well vegetated with a temperate climate in a greenhouse world with 2 to 6 times pre-industrial CO2 levels. The sedimentary record from the Antarctic margin and the deep-sea isotopic record show the first ice sheets to have formed around 34 million years ago, as CO2 levels dropped, and for the next 20 million years the ice sheets responded to orbital forcing with ice volume increases representing 30-60 m of sea level fall. Around 14 million years ago Antarctic climate cooled and the ice sheet became less dynamic. However, both Antarctic margin and deep-sea records show orbitally forced fluctuations continued, as well as a warmer Pliocene period around 3 million years ago.

The current average projection for global temperature rise by 2100 is around 3C above 1990 levels. This approaches the average global temperature prior to the first ice sheet 34 million years ago and implies that unless global CO2 emissions are dramatically reduced in the very near future we will have secured the return of the Antarctic (and the Earth) to its greenhouse state indefinitely. Reports over the last year indicate the Antarctic Ice Sheet has begun to respond earlier than expected to regional warming, and is also showing more sensitivity. Monitoring the real time changes in ice flow and mass balance, and recent new knowledge of ice sheet behaviour, will hopefully spur political action to address a problem that many thought could be left for future generations.

12 Feb. Jacqueline Flückiger , INSTAAR.
"Modeled seasonality and timing of abrupt climate events during the last glacial epoch."

The last glacial period was punctuated by 25 warm phases in the northern hemisphere, so called Dansgaard-Oeschger (D-O) events. I use the 3D coupled global ocean-atmosphere-sea ice model ECBILT-CLIO, forced with freshwater anomalies in the North Atlantic to simulate abrupt glacial climate events, which are used as analogues for D-O events. The two focuses of this talk are the seasonal character and the timing of the simulated events in different regions of the northern hemisphere.

Most parameters of the Earth system are strongly influenced by seasonality. Additionally many paleo-proxies record seasonal rather than annual mean climate conditions. It is, therefore, crucial to understand shifts in the seasonal cycle associated with climate events such as D-O events. The model results confirm that D-O events are dominated by winter temperature changes in the North Atlantic region and the high northern latitudes and show that they can be up to an order of magnitude higher than summer changes. Changes in oceanic heat transport and its seasonality as well as changes in the sea ice extent are mainly responsible for the observed patterns. However, the monthly distribution of the temperature rise is substantially different in other regions. For example, in Eurasia the largest temperature increase takes place in spring. Large regional differences are also found in the seasonality of the precipitation change.

Oceanic and atmospheric processes are involved in transmitting the signal of abrupt climate events to regions beyond the North Atlantic. Of great interest is the timing and the duration of the warming at the onset of D-O events in different parts of the northern hemisphere. I will show paleo-data from ice cores and model results indicating that some regions in the northern hemisphere undergo changes before they can be seen in the North Atlantic region. In contrast, the end of the modeled warming is much more homogenous throughout the northern hemisphere.

05 Feb. Diana Nemergut, INSTAAR.
"Microbial Diversity: What drives it and why should you care?"

We live in a microbial world; microorganisms directly influence plant, animal and human health, control major global biogeochemical cycles, and are useful for an array of biotechnologies. Much of the genetic and biochemical diversity of all of life is found within microbes, allowing these organisms to catalyze a variety of reactions central to all major nutrient cycles. The processes that generate this diversity in microorganisms are markedly different from those at work in larger organisms, and direct genetic exchange (i.e., horizontal gene transfer) is important. I will give an overview of microbial diversity; patterns of diversity in microorganisms are different from larger organisms, and recent research suggests that arctic and alpine regions may be microbial biodiversity hot-spots. I will also talk about one key mechanism that generates microbial diversity, integrons. My work suggests that integrons, which are important for generating microbial diversity on short time scales (i.e., decades), may also be important in shaping microbial diversity over billions of years.

29 Jan. Herman Sievering, Environ. Sci. & Geog., UCDHSC & INSTAAR, CU-Boulder.
"Aerosol influences on Earth’s energy balance & IPCC’s 4th Assess. Report: Planktonic S flux, seasalt chemistry and anthropogenic radiative forcing."

The Intergovernmental Panel on Climate Change (IPCC)’s 4th Assessment Report will soon be released. Global climate models (GCMs) are used extensively in IPCC assessments of anthropogenic impacts on Earth’s energy balance; i.e., anthropogenic radiative forcing (RF) in watts energy per ground area, W m-2. These GCM models have provided RF estimates with fairly well characterized uncertainty estimates as well. For example, the 2005 CO2 anthropogenic +RF is 1.63 ± 0.13 W m-2.

The negative (cooling) RF influence of anthropogenic aerosols has been invoked, successfully, to explain the relatively slow rate of global mean surface temperature increase following World War II as the world’s industries began emitting aerosols into Earth’s atmosphere with abandon (Andreae, Science 315, 50-51, 2007). The IPCC, in its 3rd Assessment Report (2000), found that both the aerosol direct effect and the cloud-enhancing, aerosol indirect effect (AIE) may contribute a –RF that substantially counters the +RF influence of greenhouse gases.

IPCC’s aerosol –RF magnitudes, including their uncertainties, will be reviewed. An atmospheric-science-community respected BGC sulfur cycle will be described that considers warming ocean surface waters followed by enhanced planktonic S emissions to the atmosphere which, thereby, increases cloud condensation nuclei concentrations and the AIE over the global oceans. The shunting of this planktonic S flux back to the surface waters by heterogeneous S conversion in seasalt aerosols, the subject of our research, will be briefly presented. Finally, the estimated –RF by aerosols and their uncertainties, once including over-ocean seasalt aerosol chemistry, will be discussed in the context of the IPCC’s upcoming 4th Assessment Report.

27 Nov. Steave Leavitt, University of Arizona.
"CO2 and tree rings: Influence on water-use efficiency and tree growth."

Theoretical and experimental evidence has suggested woody (C3) plants will experience improved water-use efficiency with increasing atmospheric CO2 concentrations. A compilation of tree-ring stable-carbon isotope chronologies reveals that instrinsic water-use efficiency (rates of assimilation to stomatal conductance) has indeed been increasing world wide over the past century or more. If real, this may have consequences to the carbon cycle, the water cycle and to tree-ring precipitation reconstructions, the latter of which is discussed.

13 Nov. Mark Hernandez, Environmental Engineering, CU-Boulder.
"Source tracking of airborne microorganisms."

While the pollution of our atmosphere continues to receive increased attention, the microbiology of air (generically termed “bioaerosol”) has largely been ignored by the engineering and science community. In the context of exposure assessment, this presentation will introduce the technical considerations for bioaerosol sampling, with the adaptation of microscopy and molecular methods to determine the identity, distribution and abundance of airborne microbes. This presentation will include a synopsis of recent research where molecular probes were leveraged for forensic source tracking. This overview will include case studies of bioaerosols partitioning from water sources from two very different environments: an indoor hospital therapy pool and the quarantined New Orleans flood zone in the weeks between hurricanes Katrina and Rita.

06 Nov. Thomas Ager, USGS.
"Ecosystem history of southeastern and south-central Alaska."

Quaternary research in coastal south-central (SC) and southeast (SE) Alaska has been relatively neglected compared with many other areas of Alaska and western Canada. Dense forest cover and logistical challenges have contributed to this, but such difficulties are not insurmountable. In recent years, important new discoveries in southeast Alaska and the Queen Charlotte Islands of British Columbia are significantly changing our understanding of late Pleistocene and Holocene changes in climate, ecosystems, and human history of the NE Pacific coast. Studies of fossil vertebrate faunas preserved in caves by Tim Heaton reveal a history of about 30 mammal species, 50 fish, and 30 bird species, some of which date back to beyond the limits of radiocarbon dating. Recent archeological discoveries by Jim Dixon indicate that human colonization began in SE Alaska at least 10,400 radiocarbon years ago. The studies summarized here provide another key piece of the puzzle needed to reconstruct the late Quaternary record of Pacific coastal Alaska: vegetation history during and after deglaciation. Peat cores and lake sediment cores have been collected by the USGS for pollen analysis from 23 sites in SE Alaska and 22 sites in SC Alaska since 1998. Some of these sites are still under study but most have been analyzed and radiocarbon dated. The earliest records from onshore sites are from SW Alexander Archipelago of SE Alaska. Pollen of herbs and shrub pollen (willows, heaths), with some pine pollen suggests that lowland tundra with scattered pines (Pinus contorta) colonized the outer coast by ca. 13,800-12,400 yr BP, probably from nearby refugia on the continental shelf. Open forests of pines, with alders and ferns then quickly spread across SE Alaska and persisted until about 10,400 yr BP, when pine populations declined rapidly and Sitka spruce forests developed in lowlands. Mountain hemlock began to colonize mountain slopes at about that time. By 9000 yr BP, western hemlock began to colonize southern SE Alaska from the south, and reached northern SE Alaska by 7000 yr BP. Cooler, wetter climates began about 7000 yr BP as suggested by the spread of coastal forests into uplands of SE Alaska. During the late Holocene, increasingly cooler, wetter climates are indicated by several neoglacial ice advances, development of more complex rainforest, and the expansion of muskeg vegetation. In SC Alaska, vegetation history following glacial retreat was somewhat different than in SE Alaska. Tundra vegetation was present at low elevations by 10,800 yr BP. Alder thickets covered much of the treeless landscape after 9500 yr BP, and persisted for thousands of years. Some coastal tree species migrating N and W from SE Alaska reached Yakutat Bay by about 7500 yr BP, but narrow coastal lowlands and major piedmont glaciers to the west created a bottleneck slowing further westward spread of trees. Sitka spruce and mountain hemlock finally reached Prince William Sound by about 3200 yr BP, followed later by western hemlock and yellow cedar in some areas. Coastal forest reaches its western limits in Cook Inlet today, where it mingles in some areas with boreal forest species from interior Alaska.

30 Oct. Patric DeDecker, Department of Earth and Marine Sciences, The Australian National University.
"Preliminary findings on the geochemical and microbiological fingerprinting of Australian aeolian dust: Implications for (past) climates, the environment, health and the oceans."

Understanding the origin and composition of Australian dust has implications on the environment, ocean and human health. However, there is scant published information on the chemical and biological composition of airborne dust from the Australian continent. For example, an isotopic comparison of aeolian material from the southern continents with dust recovered in Antarctic ice cores listed only 5 samples for the entire Australian continent, and consequently argued for a Patagonian source during glacial periods for dust recovered at Vostok.

This presentation will concentrate on an intensive, multidisciplinary and collaborative analysis of dust from the October 22, 2002 “Canberra dust storm” event. Interestingly, DNA from 75 different microbial species was extracted from the dust, and a great variety of organic compounds, including DDT, were also found. Using a variety of geochemical and palynological ‘fingerprinting’ analyses, including investigations of Nd and Sr, isotopes linked the dust that rained down in Canberra to the Bourke area of western New South Wales. Investigation of the meteorological events at this time corroborated with these results.

Further investigation of different isotopes of Nd, Pb and Sr, demonstrates that Australian dust has clearly been linked, for particular episodes of the Late Quaternary, to Antarctic ice cores. The Australian origin of the dust will be discussed.

Finally, preliminary investigations by Dr G. Allison and Mr D. Stephenson of the microbiological communities isolated from aerosols pumped at sea offshore Australia will be presented.

Discussion will lead to the potential effects of airborne dust on coral and human health, soil fertility and past and future climates.

This presentation on phenomena related to the Australian arid and semi-arid environments has direct implications for North America and the audience will be asked to comment on this aspect.

23 Oct. Hans-Peter Marshall, INSTAAR.
"Spatial variability of the snowpack: experiences with measurements at a wide range of length scales with several different high precision instruments."

Snow exhibits an extremely wide range of material properties over both short spatial as well as temporal scales compared with most other materials. Recent increases in resolution, precision, and speed of quantitative, state-of-the-art snow science instruments have made detailed measurements covering a wide range of length scales possible in a reasonable length of time. New automated unbiased measurements allow direct quantitative comparisons between measurements made by different observers, and allow 10-1000 times more data points to be collected when compared with manual measurements. This increase in data is necessary for applying geostatistical techniques to improve our understanding of spatial variability at a wide range of length scales, due to the highly variable nature of snow. Quantifying spatial variability of snowpack properties is important for calibration/validation of remote sensing measurements, snow hydrology, and avalanche forecasting. Data from three hi-tech snow science instruments (radar, penetrometer, and an automatic depth probe) collected in alpine, polar, and sea-ice snowpacks indicate that the degree of spatial variability varies widely depending on both environmental conditions and the resolution and support of the instrument used.

16 Oct. Andrew Todd, Trout Unlimited.
"Effects of acid rock drainage on stocked rainbow trout (Oncorhynchus mykiss): an in-situ, caged fish experiment."

In-situ caged rainbow trout (Oncorhynchus mykiss) studies reveal significant fish toxicity and fish stress in a river impacted by headwater acid rock drainage (ARD). Stocked trout survival and aqueous water chemistry were monitored for 10 days at 3 study sites in the Snake River watershed, Colorado, U.S.A. Trout mortality was positively correlated with concentrations of metals calculated to be approaching or exceeding conservative toxicity thresholds (Zn, Mn, Cu, Cd). Significant metal accumulation on the gills of fish stocked at ARD impacted study sites support an association between elevated metals and fish mortality. Observations of feeding behavior and significant differences in fish relative weights between study site and feeding treatment indicate feeding and metals-related fish stress. Together, these results demonstrate the utility of in-situ exposure studies for stream stakeholders in quantifying the relative role of aqueous contaminant exposures in limiting stocked fish survival.

09 Oct. Diane McKnight , INSTAAR.
"Glacial meltwater streams in the McMurdo Dry Valleys, Antarctica: ecosystems waiting for water."

Glacial meltwater streams in the McMurdo Dry Valleys, Antarctica flow for 6-12 weeks per year into the ice-covered closed basin lakes in the valley floors. These lakes have experienced a general rise in lake level since their discovery by Scott in 1903, although recently there has been a cooling trend. As part of the McMurdo Dry Valleys LTER project, we monitor stream flow in 17 streams in Taylor and Wright Valleys and study hydrologic and biogeochemical processes, such as evaporation, nutrient uptake and weathering reactions, which strongly influence the flux of water, solutes, and sediment to the lakes. Many of these streams contain abundant microbial mats composed of cyanobacteria and diatoms. Uptake of nutrients by these mats limit the nutrient fluxes into the lakes, such that streams which cannot support algal mats are the main nutrient sources to the lakes. We currently are focusing on biogeochemical and biodiversity connections in the dry valleys. For example, we have found that there are over 40 taxa of diatoms, half of which are endemic to the region. The endemic species increase in relative abundance with decreasing streamflow in cooler summers, suggesting that highly adapted organisms sustain the stream ecosystems under harsh conditions. To quantify the dominant processes acting in the streams, we employ stream-scale perturbation experiments. In one experiment we diverted water into an abandoned channel and documented the rapid growth of microbial mats. In another study, we conducted two dual-injection conservative tracer experiments at mid-day in a 143-m stream reach instrumented with temperature and specific conductance probes to understand the processes controlling the maximum daily stream temperatures, which range from 8 to 15 °C, In one experiment, the upstream temperature was lowered by continuously adding snow. Temperatures in the hyporheic zone were always cooler than temperatures in the stream. Reach and cross-sectional heat budgets showed that net radiation accounted for 99% of the warming. Cross-sectional heat budgets also indicated that evaporation, convection, conduction, and hyporheic exchange contributed to 30%, 25–31%, 19–37%, and 6–21%, respectively, of the non-radiative heat losses. Our results showed that these processes all worked in conjunction to limit stream temperatures. Further, because cooling contributions of evaporation and convection increase with stream temperature, these processes may constrain stream temperature maxima.

02 Oct. Dennis D. Eberl, USGS.
"Tales of quantitative mineral analysis: application to geological problems."

Recent advances in quantitative mineral analysis by X-ray diffraction have led to interesting and important geological applications. The technique itself will be described briefly, and then applied to geological situations, including the movement of sea ice, the provenance of river sediments, the weathering of glacial moraines, the mineralogy of A-horizon soils across the United States and Canada, and the hydrothermal alteration of crystalline rocks in ore deposits.

Dennis Eberl got his BA in geology at Dartmouth College and Ph.D. in Geochemistry at Case Western Reserve University. He taught for one year at Northern Illinois University and for six years in the Geology Dept. at the University of Illinois at Champaign Urbana. He joined the USGS in 1981 as a project chief, and has been working since then on scientific problems dealing with clay mineralogy, crystal growth, X-ray diffraction analysis, slow release fertilizer, and healing clay.

25 Sep. Andrew G. Fountain, Departments of Geology and Geography, Portland State University.
"Historic glacier changes in the American West."

Our GIS analysis of topographic maps indicate that more than 8400 alpine glaciers and permanent snow fields, cover an area greater than 650 km2 in seven western states of the American West, exclusive of Alaska. Evaluation of glacier change in several regions, based on historic maps and photos, indicate steady retreat after an enhanced retreat during the early 1900s. In some regions, the glaciers have not significantly changed due to local topographic settings that enhance snow accumulation through avalanching and wind redistribution. The dominant topographic control on glacier shrinkage is size. Smaller glaciers exhibit greater fractional area loss than larger glaciers. In addition to these "clean" glaciers, extensive areas are populated with debris-covered glaciers are important to alpine hydrology. Our preliminary estimates indicate that the area of debris-covered glaciers exceed "clean" ice areas by perhaps 3:1.

18 Sep. David Lawrence, National Center for Atmospheric Research-NCAR.
"A projection of severe near-surface permafrost degradation in a global climate model: Implications for global climate change feedbacks."

In recent decades, the Arctic has witnessed significant environmental change that include decreases in sea ice extent, increases in shrub cover, and melting glaciers. Temperatures over Arctic land are rising at roughly twice the rate of the rest of the world. Permafrost, which is defined as soil or rock that remains below 0 degrees C for two or more years, is an archetypal component of the Arctic climate system. In harmony with other aspects of change, permafrost temperatures are rising and there have been reports of significant permafrost degradation in some locations.

Results from the NCAR Community Climate System Model (CCSM3) indicate that degradation of permafrost will continue and may accelerate during the 21st century. The CCSM3 is a mathematical model of the global climate system that includes components representing the atmosphere, ocean, land, and sea-ice. The land model component is limited to simulating the top 3.5m of the ground, though this is the ecologically and hydrologically important portion; deeper permafrost is not as vulnerable at the century timescale. The present-day global distribution of near-surface permafrost in the CCSM3 compares well with observed estimates of permafrost distribution in terms of geographical extent. Projections of the fate of near-surface permafrost are assessed through simulations of the 21st century climate under various greenhouse gas emission scenarios. Under the “business as usual” emission scenario (A1B), the area containing permafrost in the near-surface layer declines by roughly 80% by 2100. Under a lower emission scenario (B1), the degradation of permafrost is less severe (~60%) but still substantial.

There are considerable uncertainties in both the magnitude and the timing of the projected near-surface permafrost degradation due to deficiencies in the model that include biases in the simulated climate, an imperfect land model, and feedbacks that are not fully-represented in the model. Nonetheless, this result in conjunction with the observed permafrost warming across the Arctic suggests that large-scale changes in permafrost are likely. The potential climate feedbacks associated with a degradation of near-surface permafrost are diverse. Changes to Arctic vegetation, hydrology, and the carbon cycle are expected in the form of expanding shrub cover and northward forest migration, enhanced runoff to the Arctic Ocean as well as expanding and retreating lakes and wetlands, and the release of large quantities of soil carbon, currently frozen in permafrost soil, into the atmosphere. These feedbacks could contribute to an acceleration of global climate change.

05 May. Ingrid Hendy, University of Michigan.
"Catastrophic collapse of the Cordilleran ice sheet during the last glacial."

Glacial-marine sediments collected from the slope of Vancouver Island document catastrophic collapse of the Cordilleran Ice Sheet several times during the Last Glacial Cycle demonstrating the vulnerability of the ice sheet to changes in global climate. Collapse indicated by the presence of IRD, begins slowly, increasing in magnitude and abruptly terminating within 500 years. These IRD events coincide with H5, H1 and H0, linked through radiocarbon age plateaus presently believed to result from shutdown of North Atlantic Deep Water formation. If the Cordilleran Ice Sheet was destabilized by sea level rise associated with North Atlantic iceberg armadas, the warm based ice sheet provides an analogy for the response of coastal regions of the Greenland and Antarctic Ice Sheets to global warming and sea level rise.

24 Apr. Carrie Morrill, NOAA/CIRES.
"Testing the North Atlantic freshwater forcing hypothesis of abrupt climate change."

The freshwater forcing hypothesis is a leading explanation for many abrupt climate changes of the last glacial and early Holocene. According to this hypothesis, the addition of freshwater to the North Atlantic from surrounding ice sheets increased the buoyancy of surface waters, slowed the Atlantic meridional overturning circulation (MOC), and altered global heat transport and climate far afield. Determining whether this is a viable cause of widespread climate change is crucial for predicting the impact of future melting of ice in Greenland and the Arctic. One major criticism leveled at this hypothesis is that climate model simulations with prescribed freshwater forcing do not show abrupt recovery of the MOC and of climate variables (e.g., temperature, precipitation) following the end of the forcing, as is observed in the paleoclimate record. I will present results from a simulation with the NCAR CCSM3 in which an abrupt recovery occurs, discuss the reasons for the rapid recovery and identify discrepancies that still exist with the paleoclimate data.

Special Tuesday Noon Talk, RL-1, Room 269
18 Apr. Dennis Darby, Old Dominion University.
"Healy-Oden Trans-Arctic Expedition (HOTRAX) and preliminary results."

Of the 700-800 cores from the central Arctic Ocean, more than 500 are 3cm diameter piston cores taken from Ice Island T-3 in the 60’s and 70’s. None of the cores are more than 8 meters and most are less than 3 meters in length. Thus the need for new core material prior to HOTRAX was critical. This coring expedition was planned to revisit some of the original T-3 core sites used to construct the Arctic stratigraphy that found average sedimentation rates were a few mm/kyr or less (Clark et al., 1980) in order to obtain better core material to reanalyze the age of this sediment using modern techniques. More recent findings from the Eurasian half of the Arctic (Jakobsson, 2000) suggest cm/kyr or higher rates. This dichotomy needs to be resolved and multiple age studies on new core material are underway.
     No paleoclimate record exists for the central Arctic that is more detailed than glacial/interglacial because of the current stratigraphy of mm/kyr. We plan to change this if the Eurasian stratigraphic age model of cm+ / kyr holds for the entire central Arctic.
      The recent swath bathymetry from the Chukchi Borderland indicates a large ice mass grounded there (Polyak et al., 2000). HOTRAX mapped this area and took cores from critical locations to determine the age of past groundings.
     Finally, dirty sea ice can help us understand this important sediment transport process in the Arctic and the circulation patterns that move this ice. Thus samples of dirty ice were obtained wherever possible.

17 Apr. Connie Woodhouse, NOAA, INSTAAR.
"Dendrohydrology: research to applications."

Tree-ring based reconstructions of past hydrologic conditions have important implications for water resource management in the Colorado River basin. However, until recently, this information has not been considered to be useful to or usable in management. This talk will discuss some new streamflow reconstructions for this region, as well as the challenges to both paleoscientists and water management personnel in applying these data to water resource planning and decision-making.

10 Apr. Cynthia Nevison, NCAR, INSTAAR Affiliate.
"Oceanic fluxes and their influence on seasonal and interannual variability in atmospheric CO2, O2/N2 and N2O."

Seasonal and interannual variability in physical ocean processes drives changes in ocean biogeochemistry and air-sea CO2, oxygen and N2O fluxes. Most seasonal and interannual variability observed in atmospheric CO2 data has been attributed to land-based processes, although the variability due to oceanic fluxes is not yet resolved. Still less is known about interannual variability in air-sea oxygen fluxes, but small variability is a key assumption that has been made in the use of O2/N2 data to partition between land and ocean carbon sinks. In this seminar, the oceanic contribution to observed seasonal and interannual variability in atmospheric CO2 and O2/N2 will be estimated based on forward runs of the MATCH atmospheric transport model using air-sea fluxes from 2 ocean biogeochemistry models and a CO2 ocean flux climatology. The use of atmospheric N2O data to interpret oceanic oxygen fluxes will also be discussed.

03 Apr. Alexander Kirdyanov, V.N. Sukachev Institute of Forest, Siberian Branch of Russian Academy of Sciences.
"Tree-ring related studies in Siberia (Russia): State of the art and prospects."

Systematic dendrochronological studies in Siberia were initiated in 1980s by the present Director of the Institute of Forest, SB RAS (Krasnoyarsk, Russia), Professor E.A.Vaganov. Since that time, our dendrochronology group has evolved into one of the leading centers in Russia for tree-ring science. At present, tree-ring width, density and tree-ring cell structure chronologies for more than 270 sites in Russia (primary in Siberia) have been collected and processed by our group. Several super-long chronologies (more than 1000 years) present excellent possibilities for dendroclimatic reconstructions.
    In this talk I will introduce our dendrochronology group in Krasnoyarsk, give an overview of the potential for dendrochronology in Siberia, and present some of the most recent studies from different sub-fields (dendroclimatology, dendroecology, dendrohistory, etc.) accomplished in our department and in collaboration with scientists from Europe and the USA. Several research project I am involved in will be also presented:
  - Upper tree-line study in Putorana (the far north of Middle Siberia);
  - Tree-ring studies in Khangai mountains (Mongolia);
  - Tree-rings and biomass in northern ecosystems (case studies from Middle Siberia).

20 Mar. John Behrendt , INSTAAR.
"Subglacial volcanism revealed by aerogeophysical surveys over the West Antarctic Ice Sheet (WAIS) - Comparisons with Iceland."

Analysis of coincident aeromagnetic and radar ice-sounding data (from the Central West Antarctica [CWA] aerogeophysical survey) over the WAIS reveals ~1000 50->1000-nT, shallow-source, "volcanic" magnetic anomalies, interpreted as caused by late Cenozoic alkaline magmatism associated with the West Antarctic rift system (WR). About 400 of these anomalies have topographic expression at the bed of the WAIS); >80% of these topographic features have <200 m bed relief. Despite the great disparities in ice volumes and volcanic activity between Iceland and the WR-WAIS area, there are similarities, (e.g. a few tuyas beneath the WAIS).
   The sources of ~18 of the anomalies, half concentrated in the area of the WAIS divide, have high bed-elevation (above sea level after ice removal and glacial rebound), very magnetic topography of high bed relief, up to 2 km. Because of their form similar to exposed volcanoes in the WAIS area with edifices primarily comprising subaerially-erupted, very magnetic volcanic flows, which have resisted glacial erosion, Behrendt et al. (2004) interpreted that these 18 high-topography, high-relief sources are subglacial volcanoes erupted subaerially during a period when the WAIS was absent.
   There are ~100 short-wavelength, steep-gradient, negative magnetic anomalies observed in the CWA survey, (~10% of the ~1000 "volcanic" anomalies), which indicate volcanic activity during a time of magnetic field reversal from normal to reversed polarity at least as old as 780 Ka (the Brunes-Matuyama reversal). One of the high topographic features, Mt. Resnik, marked by a complex negative anomaly, is a conical peak 300 m below the surface of the WAIS, and has ~2 km topographic relief. We interpret magnetic models fit to this anomaly as comprising both reversely and normally magnetized volcanic flows at the summit, erupted subaerially during a period of magnetic reversal. Published models (1996) for the Hut Point anomaly, at Ross Island, Antarctica, also required both normal and reversed magnetizations correlated with drill holes into dated volcanic flows (also part of the late Cenozoic WR) crossing the Brunhes- Matuyama boundary (780 Ka).
    While the age of the known volcanism in the WAIS area of the WR extends from the present to ~30 Ma and the WAIS has been active since >10 Ma, the age of the ice in the WAIS is 100-200 Ka at most.

13 Mar. Pieter Tans, NOAA.
"Can we still avoid major climate change caused by humans?"

The climate forcing by CO2 is approximately driven by the sum of historical emissions, not by the rate of emissions. As we continue to emit CO2, its forcing will gradually overwhelm all of the other anthropogenic climate forcing agents. Net emissions of CO2 have to be brought down to zero. The climate change problem is therefore primarily caused by our energy supply technologies and practices. Fundamental changes in energy supply and consumption will be necessary.

06 Mar. Walter Dean, USGS Denver, INSTAAR Affiliate
"Sediment geochemical records of productivity and oxygen depletion along the margin of western North America during the past 20,000 years: Teleconnections with the Atlantic and Caribbean."

Several published records from the margins of the Californias (Alta and Baja) have correlated anoxic intervals (laminated sediments) and warm sea-surface temperatures with stadial intervals as defined by the oxygen-isotope composition of Greenland ice (Dansgaard-Oeschger, D-O, cycles). These intervals include all or parts of oxygen isotope stage 3 (OIS3; 60-24 cal ka), the Bölling/Alleröd warm interval (B/A; 15-13 cal ka), and the Holocene. Organic carbon (Corg) and trace-element proxies for anoxia and productivity, namely elevated concentrations and accumulation rates of molybdenum and cadmium, in these laminated sediments suggest that productivity may be more important than ventilation in producing changes in BWO conditions on open, highly productive continental margins. The main conclusion from these proxies is that during the last glacial interval (LGI; 24-15 cal ka) productivity was lower and bottom-water oxygen levels were higher than during OIS3 and the Holocene on all margins of the Californias. The OC and trace-element profiles in the LGI-B/A-Holocene transition in the Cariaco Basin on the margin of northern Venezuela are remarkably similar to those in the transition on the northern Alta California margin. Correlation between D-O cycles in Greenland ice with gray-scale measurements in varved sediments in the Cariaco Basin also is well established. Synchronous climate-driven changes as recorded in the sediments on the margins of the Californias and from the Cariaco Basin with those recorded in Greenland ice support the hypothesis that changes in atmospheric dynamics played a major role in abrupt climate change during the last 60 ky

27 Feb. Detlev Helmig , INSTAAR.
"Where does all the dirty air go? Insights from INSTAAR's research at the PICO-NARE (Azores/Portugal) observatory."

Emissions and transport of air pollution from continents bordering the North Atlantic have been researched on top of Pico Mountain in the Azores, Portugal by INSTAAR’s Atmospheric Research Lab since summer 2004. The value of this free troposphere research site has been increasingly recognized and motivated new initiatives for incorporating this station in the Global Atmospheric Watch (GAW) network. A remotely controlled analytical system for the continuous, unattended monitoring of non-methane hydrocarbons was developed and has been operated at this site for more than a year. Data from these measurements are used to research source regions and photochemical processing of air reaching the station. A particular interest is the investigation of boreal biomass burning events, as forest fires have been shown and are predicted to further increase due to the warming and summertime drying of high northern latitude ecosystems. Air transported from biomass burning events is frequently observed at Pico during the summer. Ozone production in boreal biomass burning plumes has been found to be higher than current model predictions, which is of high interest and concern, as an increase in tropospheric ozone constitutes an important climate feedback.

20 Feb. Eugene Kelly, Colorado State University.
"The Biogeochemistry of Silica in Grassland Ecosystems of North America"

The biogeochemical behavior of silica is closely linked to that of other important elements, particularly carbon and the carbon cycle. Marine diatoms are a major control on the distribution of silica in the oceans, and also play a major role in controlling atmospheric pCO2 via the oceanic “biological pump”. A primary source of marine silica is terrestrial, yet the controls on silica cycling in the terrestrial environment are poorly understood (Kelly et al, 1998). Recent estimates suggest that the global uptake of biogenic silica by terrestrial biomass ranges from 60 to 200 Tmol yr-1 (Conely, 2002) and rivals quantities stored in the biologically active portions of the ocean systems. Importantly, the largest reservoir of biogenic silica (BSi) in terrestrial systems resides not in living biomass but in soils (Kelly et al, 2002), as BSi accumulates from inputs via the decomposition of the plant materials.
Since grasslands cover about 40% of terrestrial Earth their importance in the global Si cycle may be substantial. We conducted research to further our understanding of the primary controls on the biogeochemical behavior of silica in grassland ecosystems. Across a bioclimatic sequence (Jenny, 1941;1980) spanning major grassland ecosystems in the Great Plains, soil BSi depth distributions were found to be similar to that of soil organic carbon; however, unlike soil organic carbon, quantities of soil BSi decrease with increasing precipitation, despite an increase in annual biogenic inputs through litterfall across the same gradient. Although comprising only 1-3% of the total Si pool, faster turnover of BSi and annual cycling by grasses positively impacted mineral dissolution (Blecker, 2005). In addition, Blecker et al (in review) provided the first systematic assessment of BSi in grasslands and pointed to these ecosystems as potentially important reservoirs of BSi. Estimates for BSi in aboveground biomass in North American grasslands was determined by scaling up from long term ANPP and plant BSi data and found to be approximately 0.3 Tmol Si. Of greater interest however is the estimate of the storage of BSi in grassland soils, which was roughly 130 Tmol of Si. Thus the BSi stored in the soils of temperate grassland ecosystems alone rivals the estimated global storage in biomass. In addition, this work suggested that geochemical behavior as well as the variability of BSi within grassland ecosystems was linked closely to climate and ANPP.
Our ongoing research is designed to collect the necessary data to better understand the primary controls of soil BSi pools so that we can extrapolate beyond this single geographic region. These data will allow us to refine our understanding of grass dominated ecosystems in the global biogeochemical Si cycle and assess the global impact and concomitant rise of grasslands and diatomaceous marine deposits associated with the late Miocene (Kidder and Gierlowski-Kordesch, 2005).

13 Feb. Erin Pettit, University of Washington
"A year in the life of a polar glacier."

Polar glaciers (those in which the ice temperature is well below freezing throughout the glacier) that terminate on land have a distinctive terminus morphology: they terminate in dramatic ice cliffs, typically 30 meters high. These ice cliffs are a unique manifestation of the balance among the glacial processes of deformation, ablation, and calving. The University of Washington and Portland State University are currently collaborating on a comprehensive study of the terminus dynamics of Taylor Glacier, Antarctica, with an emphasis on the calving mechanisms, the evolution of these ice cliffs, and the role calving plays in advance and retreat of polar glaciers.
Using measurements and modeling of ice deformation near the cliff face, field observations of crevasse patterns and calving, and seismic measurements of glacier activity, I will show in this presentation the effects of the seasonal climate cycle on terminus dynamics. We find that the cold air temperatures in winter penetrate approximately 10 meters into the ice. Because the viscosity of ice is extremely sensitive to temperature, the cold winter temperatures create a stiff “shell” of ice, 5 to 10 meters thick, on the surface of the glacier, including the face of the cliff. Near the cliff, this cold shell inhibits ice flow perpendicular to the cliff face, creates winter shear zone near the cliff edge, and causes an increase in seismic activity (“Ice Tremor”). Alternatively, the warm summer temperatures soften the ice near the surface and on the face of the cliff. This softening enhances ice flow perpendicular to the cliff face and reduces seismicity. Because calving events are the result of significant ice fracturing and cold ice is more stiff and brittle than warm ice, the calving process and cliff dynamics vary significantly through the seasonal cycle. Our results suggest that this seasonal variation is important for the existence of the ice cliffs, and, therefore, for the overall dynamics of polar glacier termini.

06 Feb. Lesleigh Anderson, USGS Denver, INSTAAR Affiliate.
"North Pacific atmospheric circulation change and effective moisture variability in the Yukon Territory, Canada."

Airmasses influencing the climate of the southern coast of Alaska and the southwest Yukon originate from the Bering Sea, the Gulf of Alaska and the Arctic. Their trajectories are largely controlled by variations in the intensity and position of the semi-permanent Aleutian Low (AL) located over the Gulf of Alaska. Decadal scale variability of the AL has been recognized from analyses of instrumental data and is described by climate indices such as the North Pacific Index (NPI) and the Pacific Decadal Oscillation (PDO). Previous paleoclimatic studies suggest that variations in AL intensity and/or position were an important control of Alaska and Yukon Holocene climate. However, the combined effects of changes in circulation superimposed on regional topography produce notably different climates on the coast and the interior. We analyzed oxygen isotopes in sediment cores from two lakes with contrasting hydrological settings to improve the detail and resolution of the regional climatic history and investigate forcing mechanisms for Holocene climate change. Jellybean Lake is a small, hydrologically open lake and Marcella Lake is a similarly sized hydrologically closed lake. Both are located in the rain shadow of the St. Elias Mountains. Isotope hydrology data from the southern Yukon indicate that the oxygen isotope composition of water in Jellybean Lake reflects the composition of mean-annual precipitation. Recent changes in the d18O of Jellybean sedimentary calcite correspond to changes in the North Pacific Index (NPI) suggesting that down-core d18O variability is related to the degree of fractionation during moisture transport controlled by the intensity and position of the AL. In contrast, Marcella Lake is currently 18O-enriched by summer evaporation and past Marcella lake water values document changes in effective moisture. Results to date connect prominent atmospheric circulation variations over the Gulf of Alaska to effective moisture variability in low elevation interior regions and highlight the spatially heterogeneous response to climate change in the region.

30 Jan. Jeff Connor, National Park Service, INSTAAR Affiliate.
"The political realities of integrating research results into land management decisions: Suggestions on how to effectively present your results in a meaningful way to land managers."

Knowing the condition of natural and cultural resources in the National Parks is critical to conserving the parks unimpaired for the enjoyment of this and future generations. The National Park Service relies on scientists to provide a strong scientific basis for manage-ment actions. It is vitally important that scientists carefully consider how research results can be presented that most effectively support natural or cultural resource management. How your research will gain a better understanding in land management decisions need to be considered. Research provides ecological thresholds for parameters and trends and scientists often provide recommendations for reversing a negative trend. However, re-search funded by land managers is often only for a few years, and such funding is coun-tered by the need for a monitoring program to be structured around initial research and spatially broad factors, playing out over lengthy periods of time. Although the method-ologies employed in research is designed to be scientifically sound, choices about what and how to do the research is influenced by management information needs and cost. It is important that scientists can adaptively alter their program, but still meet rigorous scien-tific protocols if adequate funding is not available.
    There are differences on how research results should be presented to a peer audience or a broad audience that may include politicians. The first audience involves science writing, the second science communication. Scientists have to be good communicators. It is im-portant to consider who is the end users of the information and who maybe involved in a management decision. Scientists when doing research for land managers often provide a report that has an executive summary or abstract and conclusion that can include recom-mendations for management actions. Decision makers often don't have the time to read the entire report and rely solely on the executive summary or abstract and conclusion. Scientists often follow up the report with a published paper. What often fails to occur is to provide the land manager a suggested press release, sound bite or submit an article in a science document managed by the land manager. For the National Park Service, scientists are encouraged to publish their results in Park Science or the George Wright Forum jour-nals, and NPS Year in Review Highlights that are published and made available to a wide audience. Non published reports and published papers should also be submitted into the NPS Natural Resources Report Series and be listed in the NPS NatureBib program. These last two are usually done by park employees and researchers should be willing to share their data.
   Obstacles or barriers to integrating research into resource management actions can include:
* Lack of resources (people, funding, etc.) for implementing research recommendations
* Changes in priorities
* Political arena
* Multiple Audiences
* Management inertia
* Contradicting management goals within a park, or visitor enjoyment taking precedence over preservation and protection
* Research can be a slow process and take many years while decisions sometimes have to be made in days
* How to keep research on the front burner, in competition with other issues particularly for funding
* Maintaining relevance of research or resource management issues over time, staff turnover and changing priorities
* Lack of clear roles for who makes management recommendations
* NPS or Government cultural
* Public perception
* Strained relations between scientists, land managers and the public
* Decision makers are forced to make decisions without adequate information
*Communication between scientists and land managers are inadequate
   Scientists need to understand that land managers appreciate the recommendations from research, but sometimes decisions are politically made or other factors are worked into the decision. If you find that a management action is not working, it is good to say so in a diplomatic way. Offer suggestions on how to correct the action. Land managers using scientifically sound research in making a decision have stuck their necks out and some have lost their jobs or been run out of town or the state on a rail due to the outcry from special interest groups, politicians or politically appointed people. It is important to un-derstand that federal or state land management employees do not work in a democracy. The majority does not rule, but these employees are often dedicated and maintain their integrity even when their jobs are threatened. Decisions are sometimes made in their ca-reers when it is best to draw a line in the sand and when it is best to retreat to fight an-other battle another day.
    I will present strategies for breaking down obstacles and barriers listed above. I will also present some examples of well carried out research that was implemented into Manage-ment Plans, but the alternative selected in the Environmental Impact Statement ignored the research and the long-term consequences of the action had serious ramifications to the natural environment and human health and safety. Examples will also include dedicated career employees forced into a directed reassignment into a dead end job, or one they did not want, when they drew a line in the sand based on good research.

28 Nov. Hans-Peter Marshall, INSTAAR.
"Snowpack spatial variability: towards understanding its effect on remote sensing measurements and snow slope stability."

The distribution of water in the snow-covered areas of the world is an extremely important climate change indicator, and it is a vital component of the water cycle. At local and regional scales, the snow water equivalent (SWE), the amount of liquid water a given area of the snowpack represents, is very important for water resource management, flood forecasting, and prediction of available hydropower energy. Measurements from only a few automatic weather stations, such as the SNOTEL network, or sparse manual snowpack measurements are typically extrapolated for estimating SWE over an entire basin. Widespread spatial variability in the distribution of SWE and snowpack stratigraphy at local scales causes large errors in these basin estimates. Remote sensing measurements offer a promising alternative, due to their large spatial coverage and high temporal resolution. Although snow cover extent can currently be estimated from remote sensing data, accurately quantifying SWE from remote sensing measurements has remained difficult, due to a high sensitivity to variations in grain size and stratigraphy. In alpine snowpacks, the large degree of spatial variability of snowpack properties and geometry, caused by topographic, vegetative, and microclimatic effects, makes prediction of snow avalanches very difficult.
Ground-based radar and penetrometer measurements can provide a means for quickly and accurately characterizing snowpack properties and SWE in the field. The development of a portable lightweight FMCW radar combined with new data acquisition and processing software, allows a real-time estimate of SWE to within 10\%, as well as measurements of depths of all major density transitions within the snowpack. A physics-based theory of snow penetration has been developed, allowing accurate estimates of mechanical properties as well as an index of grain size to be retrieved from the SnowMicroPenetrometer. These two tools together allow rapid characterization of the snowpack's geometry, mechanical properties, and SWE. New analysis techniques are applied to data collected from the last two winters in Colorado, Alaska, Switzerland, and the Canadian Arctic. The ability to accurately characterize snowpack properties at much higher resolutions and spatial extent than previously possible will hopefully help lead to a more complete understanding of spatial variability, its effect on remote sensing measurements and snow slope stability, and possibly result in improvements in avalanche prediction and accuracy of SWE estimates from space.

21 Nov. Sarah Spaulding, USGS Denver, INSTAAR Affiliate.
"Report on algae in streams in North America: diatoms are behaving badly."

In this presentation, I will examine the regional distribution and spread of a diatom species in North American streams. Algae are found in nearly all freshwater, from the least impacted lakes and streams to the most polluted. The species composition and abundance of algae, including the group of algae called diatoms, are reflective of the environmental quality of freshwater habitats. Historically, Didymosphenia geminata was a native to northern latitude and high elevation lakes and streams. The species was considered to be restricted to low nutrient, low temperature habitats with little anthropogenic impact, and was an indicator of pristine condition.
     In recent years, the distribution of D. geminata has changed. This species is unusual, because it is a native species that adopted the characteristics of an invasive species. Didymosphenia geminata is forming massive growths both within and outside its native range. Not only is this diatom expanding its extent to lower latitudes and elevations, it increasingly forms extensive masses covering streambeds. Didymosphenia often covers stream surfaces, forming dense mucilaginous mats up to several centimeters in length. The organism also has a dramatic spatial extent, illustrated by its dominating the periphyton community for over 80 km of the Kootenai River in Montana.
      The trophic level impacts of this diatom are not yet documented. It is clear that other algal species are excluded from stream habitats, because the dense mats prevent the growth of other algal species. Large growths of D. geminate are correlated with a decrease in abundance of some aquatic invertebrate species and an increase in chironomid larvae. Didymosphenia masses are associated with a decrease in fisheries in some parts of the country, most likely due to the loss of invertebrate prey species.
      The proliferation of D. geminata is the result of a complex process, and is thought to be mediated by 1) low caused by drought, 2) stable flow in regulated rivers, 3) increased dispersal aided by human activities, and 4) increased flux of UV-B, which differentially impacts aquatic organisms.

14 Nov. Reto Knutti, National Center for Atmospheric Research (NCAR).
"Uncertainty in projections of future climate."

Estimates of impacts as well as adaptation and mitigation strategies related to anthropogenic climate change require a precise understanding of the anticipated changes as well as the uncertainties associated with it. Those ranges of uncertainties were based on expert opinion only for many years, and only recently a few new methods were suggested to objectively quantify uncertainties. Using large ensembles with a coupled model of intermediate complexity, probabilistic projections are presented for a series of SRES scenarios as well as for long-term stabilization scenarios which will be part of the forthcoming IPCC Fourth Assessment Report. Furthermore, a method is proposed to use the observed amplitude of the seasonal cycle to constrain climate sensitivity and thus narrow uncertainties in future projections.

31 Oct. Fortunat Joos, Climate and Environmental Physics, University of Bern. NCAR visiting scientist.
"Climate-carbon cycle interactions"

The man-made increase in atmospheric CO2 and the resulting perturbation in climate pose serious risks for the human society. While it is becoming clear that anthropogenic greenhouse gas emissions have a long-term impact on climate, we are still at the beginning of a quantitative and detailed understanding of the interactions among the physical climate system and the biogeochemical cycles. Palaeo-data provide the opportunity to evaluate Earth System models under different climate forcing conditions and on time scales that are longer than those of the available instrumental records.
The presentation will provide a brief overview on the coupled carbon-cycle climate system. A few illustrative examples of past and future changes in the Earth system will be discussed. Large scale processes and climate-carbon cycle interactions are quantified with the help of numerical models, modern observations, and palaeodata.

17 Oct. Cory Cleveland, INSTAAR.
"Nutrient controls over C cycling in tropical rain forests."

Biosphere-atmosphere carbon dioxide (CO2) exchanges are dominated by tropical forests, where even small changes in carbon (C) fluxes could profoundly alter global climate and atmospheric composition. In spite of the overwhelming importance of tropical forests in the global terrestrial C balance, the factors that influence C storage and losses in these ecosystems are still poorly understood. However, while direct evidence is rare, low soil nutrient availability is often cited as the most important regulator of tropical biogeochemical cycles. Thus, we are testing the widely accepted (but rarely tested) idea that low soil nutrient availability limits C cycling in these globally significant ecosystems. Several years of data now show that nutrient availability strongly regulates rates of organic matter decomposition, with evidence that increased atmospheric nutrient deposition in tropical latitudes may accelerate soil C losses. Nutrient fertilization doubled soil respiration during the rainy season, effectively increasing the proportion of C that is rapidly lost as CO2, and decreasing the chances of long-term C stabilization in soil. These data suggest that potential future increases in tropical net primary production (NPP) could be outpaced by nutrient stimulated soil C losses. Finally, our recent data reveal intriguing connections between rainfall, nutrient availability and C balance, and provide the basis for current research investigating how climate variability affects C cycling in a tropical rain forest in Costa Rica.

10 Oct. Irina Overeem, INSTAAR.
"Numerical modeling of the impact of an enhanced monsoon on the Ganges-Brahmaputra river system."

Reconstructions of the Ganges-Brahmaputra fluvio-deltaic system based on a stratigraphic and geochronologic database including more than 50 boreholes and 71 radiocarbon dates, showed pronounced differences in sedimentation rate over time. The Ganges-Brahmaputra River delivered ~ 2.5 times its present load to the Bengal basin between 11-7 kyrs BP. High sedimentation rates coincided with an enhanced monsoonal regime at Early Holocene times. Global sea-level rise was 20-30 m over this period. It is inferred from the sedimentological data that the two opposing forces balanced, i.e. rising sea-level versus increased river flooding and sediment flux, and a stable coastline was maintained under 20-30 m sea-level rise.
     We linked two numerical simulation models, HydroTrend and SedFlux-3D, to get more insight in the specific processes controlling the strongly increased sediment flux as well as the effect of an enhanced monsoon on a large-scale fluvio-deltaic system.
     HydroTrend numerically models the hydrological balance in a river basin and predicts discharge and sediment load time-series based on drainage basin properties (drainage basin area, hypsometry, relief) and climate (a.o. precipitation, temperature, glacier dynamics). SedFlux-3D, a stratigraphic numerical model, subsequently ingests HydroTrend sediment flux predictions. Other important boundary conditions are initial geometry of floodplain and shelf, and a time-continuous sea-level curve. A suite of process modules, e.g. stochastical channel switching, hypopycnal plume sedimentation, and subsidence and compaction, interact to predict the distribution of sediments over a basin.
     We ran HydroTrend experiments under present-day climate conditions for three main subbasins: the Ganges, the Tsangpo and Lower Brahmaputra Rivers. There is a good match between the predicted mean annual discharge and observed data for both the Ganges River (12 % deviation) and the combined Brahmaputra River (less than 6% deviation). The annual peak months are captured within 5%. These comparisons make us confident that HydroTrend mimics the present-day hydrological processes and their monthly dynamics well. The simulated sediment rating curves showed that to increase the mean sediment load with a factor 2.5, as inferred from the field data for the Early Holocene, discharges need to go up approximately a factor 1.5-1.6. This increased discharge estimate is notably higher than precipitation increases tentatively estimated based on independent paleo-monsoon proxies. We postulate that apart from an increase in precipitation, thresholds in the sediment production mechanisms were overcome during the period of enhanced monsoon.
     Generic SedFlux-3D simulations of the Ganges and Brahmaputra Rivers show initially two distinct depocenters and slow progradation into the paleo-Bengal basin at Early Holocene and more rapid progradation in the Late Holocene. However, there is a significant uncertainty in paleo-bathymetry and channel switching rates of either the Brahmaputra and Ganges Rivers, resulting in markedly different stratigraphic realizations. The numerical modeling of the linked hydrological and sediment transport processes allows unraveling of the dominance of different processes and helps to put focused field studies into larger perspective.

03 Oct. Jean-Pierre Gattuso, Laboratoire d'Océanographie de Villefranche sur mer, France. National Center for Atmospheric Research (NCAR) visiting scientist.
"Response of marine ecosystems to elevated carbon dioxide and biogeochemical consequences."

The atmospheric partial pressure of CO2 (pCO2) has increased by more than 30% during the past 120 years and is poised to increase even more in the near future. This change, due to anthropogenic activities, drives a significant increase of pCO2 and dissolved inorganic carbon in the surface ocean but also results in a decrease of the carbonate ion concentration and of the saturation state of calcium carbonate (CaCO3). Recent papers demonstrate that the saturation state of aragonite and calcite is one of the factors controlling calcification, both in temperate and tropical benthic organisms (corals and calcareous algae) and in planktonic organisms with large geographical distribution (coccolithophorids and foraminifers). In this seminar, I will review the ecophysiological, ecological and biogeochemical aspects of this major environmental change.

26 Sep. Robbie Toggweiler, GFDL/NOAA, Princeton.
"Origin of the 100,000-Yr Cycle in Atmospheric CO2."

Atmospheric CO2 has varied over the last half million years with a sawtooth- shaped cycle with a period of roughly 100,000 years. It is widely believed that this cycle is linked to 100,000-yr variations in the eccentricity of the Earth's orbit and that CO2 is acting in some way to amplify the eccentricity forcing. In this talk I will develop an alternative in which the 100,000-yr cycle is internal to the Earth's CO2/climate system. The shape and period of the 100,000-yr cycle emerge from well known geochemical processes. The main feature of the proposed mechanism is a climate threshold that, when crossed, drives the pCO2 away from its long-term mean. An interaction between the slow weathering of silicate rocks on land and the burial of CaCO3 in the deep ocean then holds the pCO2 away from its long-term mean for about 50,000 years before the threshold can be crossed again. Two such encounters with the threshold make up the 100,000-yr cycle. Quasi-random climate perturbations like Heinrich Events play a major role in this idea: the big 100,000-yr cycle bubbles up from noise-like variations like Heinrich Events with very short time scales.

12 Sep. Scott Peckham, INSTAAR.
"Hydrologic modeling and terrain: Advances in computational and visualization methods."

Modern spatial hydrologic modeling relies on digital elevation models (DEMs) for everything from computing slopes and contributing areas to computing clear-sky radiation and modeling elevation-dependent rainfall and snowfall. However, limited vertical and horizontal resolution in even the best DEMs leads to challenging computational problems that must be solved before accurate modeling is possible. Two of the key problems are (1) how to compute accurate estimates of channel slope and aspect when vertical resolution is limited and (2) how to compute accurate estimates of contributing areas and flow paths over complex terrain and divergent hill slopes. The author has developed new grid-based methods for solving these two problems that will be shown to yield dramatic improvements over existing methods. The solution to the first problem shows that it is sometimes possible to do what would at first seem to be impossible, namely to accurately reconstruct or recover much of the fine-scale topographic detail that was lost in the process of DEM creation. The solution to the second problem will be illustrated with visually provocative "flow path" images generated for the complex topography near Mount Sopris, Colorado. These methods go beyond simply providing more accurate modeling results; they also suggest new ways to tackle a number of difficult scientific questions through modeling. The author will also highlight some other new tools that he has developed in support of the TopoFlow hydrologic model. One of these tools computes clear-sky radiation over time as a spatial grid sequence or animation with subhourly timesteps. This tool uses DEM-derived slope and aspect grids, as well as celestial mechanics and climate variables such as temperature and humidity. New tools for interacting with spatial grid sequences will also be demonstrated, such as an animated profile tool that makes it easy to visualize storm-induced flood waves as they move downstream.

31 Jan. William Bowman, INSTAAR.
"Are we there yet? Critical N loads for alpine vegetation and ecosystem response."

Atmospheric nitrogen deposition has been linked to several environmental problems, including changes in ecosystem structure and function and plant susceptibility to abiotic and biotic stress. The susceptibility of communities to anthropogenic alterations in diversity associated with changes in the N status of soils is related to the background soil fertility through its influence on plant species traits, as well the proportional change in N pools associated with N deposition. Where rates of nutrient cycling are low due to physical environmental constraints, plant characters favoring slow growth and low tissue turnover are favored. Under these conditions the capacity of the dominant species to respond to increased N availability is thus limited, and changes in diversity are more probable. N critical loads and N saturation of ecosystems is generally is usually assessed by measuring leaching of inorganic N and changes in soil N cycling rates. However the "critical load" assessment in class 1 areas (National Parks and wilderness areas) is associated with changes in the most sensitive components of the ecosystem. It is not generally known whether changes in terrestrial diversity precede changes in ecosystem functional components. Fertilization experiments have indicate relatively low thresholds of N input elicit community changes in nutrient poor communities. In alpine dry meadows diversity responses occur at 4-10 kg N ha-1 yr-1, while changes in soil inorganic N pools and nitrification occur at inputs between 10-20 kg N ha-1 yr-1. Thus the change in plant diversity is a more sensitive indicator of anthropogenic N inputs in the alpine, and may make a better basis for N critical loads. Several indicators suggest changes in the diversity of alpine vegetation associated with N deposition is ongoing in the Front Range of the southern Rocky Mountains. Increases in the abundance of species with faster growth rates and higher tissue turnover rates may increase community-level uptake rates of soil inorganic N, but may also enhance rates of soil N cycling. Conceptual models based on field experiments and observations indicate that latter effect (stimulation of N cycling) is greater than the former (greater plant uptake of N) in the alpine, potentially leading to an acceleration of inorganic N fluxes between terrestrial and aquatic ecosystems.

24 Jan. Detlev Helmig, INSTAAR.
"Ozone smog at South Pole? New data from a tethered balloon experiment reveal unexpected atmospheric chemistry in the Antarctic troposphere."

The distribution of ozone in the surface and planetary boundary layer was studied during the 2003/2004 Antarctic Tropospheric Chemistry Investigation (ANTCI) at South Pole, Antarctica from Dec. 13-30, 2003. A tethered balloon sampling platform was utilized for high spatial and temporal resolution measurements of ozone, temperature, wind speed, wind direction and water vapor between the surface and 500 m above ground. During several occasions ozone production of up to ~ 20 ppb was observed in the surface layer. These periods lasted several days and coincided with conditions of suppressed vertical mixing. The data further emphasize that ozone is produced in the Antarctic planetary boundary layer during the austral summer by photochemical reactions and due to the presence of large amounts of NO emitted from the snow. This process is amplified during the Antarctic ozone hole period from increased levels of UV radiation reaching the surface. The tethered balloon data allow an in-depth analysis of the meteorological and chemical conditions that determine ozone production and transport at South Pole. This presentation will include a video presentation of the South Pole experiment.

29 Nov. John Behrendt, INSTAAR.
"Shallow-source magnetic anomalies observed over the West Antarctic Ice Sheet (WAIS) require extremely high magnetization in the present field direction. "

Study of a block of coincident aeromagnetic and radar ice-sounding data
acquired in the 1990s over the central area of the WAIS reveals about 1000 50-
>1000-nT magnetic anomalies, whose steep gradients indicate have their sources
essentially at the glacier bed. The anomalies are caused by subvolcanic
intrusions of interpreted late Cenozoic age. About 400 of these anomalies
(conservatively selected) have topographic expression as revealed by the bed
elevation map. More than 80% of these topographic features have <200 m relief.
I interpret this result as an indication of removal of volcanic edifices
comprising hyaloclastite adn other volcanic debris injected into the moving ice
during eruption as discussed in several recent papers. However, the
significance of the high magnetizations and >2-km thickness of the subvolcanic
intrusions beneath the relatively low amplitude bed topography required to
produce the observed anomalies as been insufficiently emphasized. About 18 of
the anomalies, half concentrated in the area of the WAIS divide, have high-
elevation-, very magnetic-topography of high bed relief, up to 1600 m. There
are no high bed-relief (>600 m) magnetic anomaly sources that do not have high-
elevation topography. ALL of these high-topography magnetic sources would be
above sea level after ice removal and glacial rebound. Because of their form
similar to exposed volcanoes in the WAIS area with edifices primarily
comprising subaerially- erupted, very magnetic volcanic flows, which have
resisted glacial erosion, we infer that these high topographic volcanic sources
are also subaerially erupted volcanoes.
One of the significant subglacial high-topographic features is Mt Resnik
(centered at 80°, 9' S, 116°, 20'W). Several models calculated to fit the
magnetic anomaly over Mt Resnik, indicate a reversely magnetized, 500-2500-m
thick cap of inferred volcanic flows overlying a 2-3-km thick, normally
magnetized section. Mt. Resnik is part of a 35-km by 50-km wide, <400-m high,
topographic structure, about 1 km beneath the ice surface, which we interpret
as contemporaneous in origin with the high peak of Mt. Resnik. The Mt Resnik
volcano was erupted subaerially, during a time that included a reversal of the
magnetic field from normal to reversed direction. The summit flows of Mt
Resnik, having reversed magnetization, must be older than 780 Ka. (Brunhes-
Matuyama magnetic reversal).

22 Nov. Richard Madole, USGS.
"Genesis of the Great Sand Dunes, South-Central Colorado."

Geomorphic and stratigraphic evidence obtained in recent field studies indicate that the sand in the Great Sand Dunes came primarily from a lacustrine source rather than from flood-plain deposits of the Rio Grande, as previously supposed. The source of the sand in the Great Sand Dunes has been pondered for more than a century, but since the 1960s, the idea that the flood plain of the Rio Grande was the source has been widely accepted. Closely linked to the issue of source are questions about when and under what conditions the sand was transported. Although most recent publications do not assign dates to the time of dune formation, a few infer that the process began about 12,000 years ago and link it to increased discharge and sedimentation during deglaciation of the San Juan Mountains.
The Great Sand Dunes are a small part (<10%) of an area of windblown sand that blankets the east side of the San Luis Valley for a distance of about 75 km. The distribution of this sand suggests a relationship with the closed basin part of the San Luis Valley, which is at the foot of the Sangre de Cristo Mountains north of the Rio Grande, rather than with the Rio Grande itself. This body of eolian sand is nearly coincident with the length of the closed basin, and the parabolic dunes north of the Great Sand Dunes indicate a sand source and transport direction unrelated to the Rio Grande. Also, leeside dune belts, which typically flank riverine sand sources, are conspicuously absent along the leeside of the Rio Grande.
Stratigraphic evidence and numerical ages indicate that eolian sand along the east side of the San Luis Valley is the product of multiple episodes of transport. The first major episode occurred in the middle Pleistocene after a channel that was eroded across the Taos Plateau connected the lower Rio Grande with the San Luis Valley and drained a lake that occupied a large part of the valley. Subsequently, during times of greater effective moisture and high water table, smaller lakes existed in the closed basin part of the valley that remained north of where the Rio Grande now crosses the San Luis Valley. During megadroughts, water table fell and exposed areas of sandy sediment on dry lakebeds to wind erosion. The dry lakebeds became primary sources of new generations of dune and sheet sand. At the same time, drought reduced vegetation on deposits of older eolian sand allowing wind to remobilize parts of them. During wetter times, the sand supply on the basin floor was replenished by inflow from streams that originated in the surrounding mountains. Today, most streams entering the closed basin from the mountains disappear within 1-3 km from the mountain front. They are lost primarily to infiltration into eolian sand and other basin-fill sediment.

*Special day and time, 4 pm
27 Oct. Laurens Ganzeveld , Atmospheric Chemistry Division, Max-Planck Institute for Chemistry.
"Global modelling of reactive trace gas exchanges: Uncertainties and challenges for non-vegetated and polar landscapes."

During the last decade, explicit representations of reactive trace gas surface exchanges have been introduced in global scale chemistry and transport models such as the chemistry-climate model ECHAM (European Center Hamburg Model). Those representations include prescribed anthropogenic emissions, dry deposition and biogenic emissions as a function of the micrometeorology, surface cover (including snow) and land use properties. Such an explicit representation of surface trace gas exchanges offers the opportunity to apply models like ECHAM for scenario analyses of the impact of land cover and land use changes on global atmospheric chemistry. However, there are still many uncertainties simulating reactive trace gas exchanges due to a limited amount of observations over snow, bare soil and oceans. I will address the most critical needs for experimental observations for improved model applications to quantify reactive trace gas exchanges. In addition, I will show an example of analysis of the impact of tropical deforestation on the hydrological cycle and atmospheric chemistry

25 Oct. Mike Ryan, USDA Forest Service, Rocky Mountain Research Station.
"Carbon allocation in forest ecosystems."

Carbon allocation helps control plant growth and ecosystem carbon storage by shifting photosynthesis between ephemeral and long-lived tissues and between respiration and biomass. Poor understanding of carbon allocation limits our ability to realistically model ecosystem metabolism and how carbon stored in ecosystems will change with changes in resources and environment. I review carbon allocation across broad gradients of forest productivity and for ecosystems where resources were modified in place. I determine the limits and controls of three components of allocation: biomass, the amount of material present; flux, the flow of carbon to a component per unit time; and partitioning, the fraction of gross primary productivity to a component per unit time.
In forests, patterns in biomass do not indicate current flux or partitioning. Above and belowground productivity (fluxes) were related across a broad gradient of forest productivity, with more productive sites partitioning less belowground. Within sites and species, increased resources (water and nutrients) reduced partitioning to belowground, and increased partitioning to wood, but did not change partitioning to respiration. Partitioning to below and aboveground production (but not respiration) changed with stand age, but changes differed among species. Competition did not change partitioning. Changes in partitioning within a site were much less than differences seen across sites.

11 Oct. John Andrews, INSTAAR.
"Holocene records of ice-rafted detritus (IRD): existing models and a new method."

Two great streams of ice drift southward along the margins of East Greenland and the Eastern Canadian Arctic. They consist of a mixture of sea ice and icebergs in quite different proportions between the two margins (differ by a factor of ~35). Variations in the extent of these have profound influences on both atmospheric and ocean circulation.
The present literature of IRD variations in the North Atlantic regions for the last 12,000 cal yrs is dominated by a model that shows a trend toward a decrease in IRD over the last 12,000 yrs with significant oscillations spaced about 1500 yrs apart. These data contrast with IRD measurements on the East Greenland shelf which show relatively little IRD during the Holocene "thermal maximum" and a substantial ramping up of IRD delivery over the last 6000 yrs (a period called the Neoglacial). These two contrasting scenarios need to be reconciled. To do this we employ a new quantitative XRD method for obtaining weight % data of mineral species that are exotic to various areas-such as dolomite for the Labrador shelf and quartz for the Iceland shelf. The veracity of this argument is examined by an analysis of surface sediments from around Iceland that show quartz follows the historical range of drift ice. Downcore measurements at 20-30 yr spacing on one well dated core (MD99-2269) reveal substantial low and high frequency variations in quartz and in the quartz/plagioclase ratio. As the driftwood from northern Iceland has been tracked dendrochronologically to Russia it is felt that the quartz most likely originates from the entrainment on and in the sea ice along the Eurasian margin, but some might also come from icebergs sourced in East Greenland.
(work made possible by the assistance of Dr Dennis Eberl, USGS, Boulder)

03 May Adina Payton, Department of Geological and Environmental Sciences, Stanford University.
"Phosphorus Cycling in the Ocean: New Approaches."

Phosphorus is an essential nutrient utilized by all living organisms. It has been recognized as a limiting nutrient in some oceanic systems and is possibly the ultimate limiting macronutrient for marine productivity over long time scales. Primary producers obtain most P as dissolved orthophosphoric acid, although P from dissolved organic compounds may also be used. The regeneration of dissolved inorganic P (DIP) and dissolved organic P (DOP) from particulate organic P (POP), and upwelling of these dissolved constituents to the euphotic zone, is the most important P source supporting biological productivity in the ocean. Thus, POP regeneration is a critical step in regulating P availability and biological productivity. The organic P compounds that escape regeneration at shallow depths and are exported to the deep ocean are similarly important, because these compounds are the P resource for the deep ocean benthic community. In addition, the sinking particulate P pool is the source of P to marine sediments. These sediments are a sink that at steady state is equated with input fluxes to the ocean, which in turn affects oceanic productivity and organic carbon burial. Relatively little is known about the concentrations, P bioavailability, P limitation, turnover rates, transport and fate of P in the ocean and practically nothing is known about the composition and changes in composition of this pool with age/depth and location in the ocean. The processes controlling the extensive biodegradation of sinking particulates remain unclear, partly because no information exists with regard to the composition and distribution of the residual organic matter at depth. New approaches are applied to shed light on these important oceanic processes.

19 Apr. Joe Yaritt, Natural Resources Department, Cornell University.
"Predictable (?) patterns of methanogenesis in wetlands of the discontinuous permafrost zone."

The discontinuous permafrost zone is truly a new frontier for soil microbiologists, and study is especially pertinent in light of rapid permafrost melting in recent years. Much of our knowledge about bacterial methanogenesis in soil comes from study of boreal and cool temperate peatlands, and I will apply knowledge about methanogenesis in better-studied soils to patterns of methanogenesis in permafrost soil. The study considers three habitats: a) continental bogs that show no evidence of permafrost, b) permafrost plateaus, and c) internal lawns that are melted permafrost. Specific studies include rates of bacterial methanogenesis; aspects of soil chemistry; and, clone libraries based on 16s rDNA gene sequences to characterize methanogens. Results suggest that methanogens in discontinuous wetlands are very similar, although simpler composition than methanogens in boreal and cool temperate counterparts.

12 Apr. Greg Tucker, CU Geological Sciences/CIRES.
"Climate change and the dynamics of drainage basin evolution."

It is well known that landform characteristics vary with climate, and that changes in climate can leave a lasting imprint on topography and the sedimentary record. Much less is known, however, about how and why these relationships exist. This talk explores the dynamics of landscape change in response to varying climate, using landscape evolution modeling as a theoretical device to formulate hypotheses and make testable predictions. Simulations are used to explore the origins of cycles of erosion and aggradation in valley systems. The dynamics emerging from the models are compared with case studies from North America and Australia. We will also explore how the natural stochastic variability of weather and climate can be incorporated into models of long-term river basin evolution. Overall, the results emphasize the importance of nonlinearity in geomorphic systems, and variability in the climate that drives those systems.

05 Apr. Nichole Barger, INSTAAR.
"Nitrogen dynamics of biological soil crusts on the Colorado Plateau."

Biological soil crusts are communities of fungi, lichens, cyanobacteria, and mosses that colonize soil surfaces in arid and semi-arid ecosystems. Associated soil cyanobacteria and bacteria species within biological soil crusts fix atmospheric N2 and are an important source of nitrogen in many aridland ecosystems. On the Colorado Plateau, estimates of N fixation by biological soil crusts range from 1.3-9 kg N/ha/yr depending on biological crust composition. However, low rates of N accretion in aridland systems are generally less than 1 kg N/ha/yr, leading to uncertainty regarding the fate of fixed N by biological soil crusts and the dominant N loss pathways in aridland ecosystems. In this talk I present data on N gas loss (N2O, N2, NH3) and dissolved N loss in water erosion from a series of rainfall simulation experiments.

Sorted circles, meter scale patterns consisting of circular soil domains surrounded by raised annular stone domains, are found in Arctic and high alpine environments in which the upper most layer of soil (the active layer) experiences cyclic freezing and thawing. In addition to the striking circular plan form, these patterns exhibit a convex upward soil domain surface on which motion is outward from the center, tilt in the subsurface consistent with circulation and a roughly 3-to-1 aspect ratio. Sorted circles are just one of the many incredible sorted patterns found in these environments, including: polygons, labyrinths, islands and stripes.
     A diverse range of formation mechanisms have been suggested. These span the gamut from convective instabilities to the toils of ancestors. Frost heave, soil expansion by water migration during freezing, is the prime mover in the active layer, but what organizes that motion? We propose that sorted circles arise from a robust positive feedback between the morphology of the stone-soil interface and frost heave at that interface, which pushes stones upward and transports soil toward regions with high concentrations of soil.
     This feedback has been incorporated into a three-dimensional numerical model in which stone and soil particles are transported between lattice cells by processes associated with freezing and thawing (frost heave, soil compaction, soil creep, illuviation, and soil swell by water absorption). In this model, sorted circles emerge from an initial configuration in which a uniform layer of stones overlies a layer of soil. Linear stability analysis of this positive feedback mechanism accurately predicts the initial wavelength of perturbations on the stone-soil interface; however, the size and spacing of sorted circles is not given by this initial instability. Finite amplitude effects and interactions between neighboring soil domains must be considered to understand the characteristics of modeled sorted circles observed at the ground surface.
     An abstraction of this soil accumulation feedback was incorporated into a two-dimensional (plan view) numerical model along with stone transport owing to deformation of stone domains by frost heave in soil domains. In this model, patterns develop through feedbacks between local stone domain shape and stone transport. Depending on the abundance of stones and the strength of these two transport mechanisms, circles, islands, mazes or polygonal net patterns can emerge from an initially random distribution of stones.

15 Mar. Alex Wolfe, University of Alberta.
"An archaeometallurgical history of the southern Bolivian Andes: the case for missing silver."

Pre-Columbian metallurgy in South America is poorly constrained because looting of metal artifacts has been pervasive. Lake sediments offer an attractive alternative medium for reconstructing early mining, because metals associated with smelting can provide faithful time-series of metallurgical activity at the regional scale. This approach has been used to infer a millennium of silver extraction from Cerro Rico de Potosí, the world's largest silver deposit in the central Bolivan tin belt. Marked enrichments of metals associated with the smelting of local argentiferous ores (Pb, Sb, Bi, Ag, Sn) reveal two phases of intense mining activity, first during the terminal stages of Tiwanaku culture (1000-1200 A.D.) and again during Inca through early Colonial times (1400-1650 A.D.). The earliest of these events suggests that Cerro Rico ores were actively smelted at a large scale in the Late Intermediate Period, providing compelling evidence for a major pre-Incan silver industry that is nowhere manifested by the record of sliver artifacts.

08 Mar. Greg Asner, Carnegie/Stanford.
"Grazing systems in the global environment."

Managed grazing covers more than 25% of the global land surface and has larger geographic extent than any other form of land use. Grazing systems persist under marginal bioclimatic and edaphic conditions of different biomes, and this has led to the emergence of three regional syndromes inherent to global grazing: desertification, woody encroachment, and deforestation. These syndromes have had widespread but differential effects on the structure, biogeochemistry, hydrology, and biosphere-atmosphere exchange of grazed ecosystems. In combination, these three syndromes represent a major component of global environmental change.

01 Mar. Jeff Lukas, INSTAAR.
"Reward of the rings: Ancient trees provide multi-century records of drought and streamflow in Colorado."

Sustainable water management in the West requires knowledge of the natural variability in climate over time, to plan for probable future conditions. We have developed a dense network across Colorado of 60 moisture-sensitive tree- ring chronologies, 300-800 years long, creating a unique resource for hydroclimatic reconstructions. This network is now the basis for collaborative work with major Colorado water providers to develop high-quality streamflow reconstructions for gages critical to water management in the Upper Colorado, Gunnison, and South Platte River basins. The reconstructions explain 63% to 76% of the variance in the gaged records, and replicate drought events particularly well. The reconstructions indicate that the variability seen in the gaged record is not representative of the prior two to five centuries, and that the extreme single-year (e.g. 2002) and multi-year (e.g. 1930s) drought events in the gaged record have been exceeded in severity in the past. Even so, the 2002 drought is remarkable for its combination of severity and spatial extent. Besides providing high-resolution paleoclimatic records, the sampled ancient pinyon pine, ponderosa pine, and Douglas-fir trees represent xeric old- growth ecosystems of great diversity and surprisingly widespread distribution. The history of their establishment--and their persistence on the landscape for up to 1000 years--could shed light on temporal and spatial patterns of disturbance, and possibly on centennial-scale climate variability as well.

23 Feb. Najat Bhiry, INSTAAR Visiting Scientist, Université Laval
" The temporal and spatial impacts of fluctuating climates on Nordic ecosystems development (e.g. evolution of peatland palsas of northern Canada)."

Plant macrofossil data allowed the reconstruction of the developmental history of two peatlands palsas located in subarctic Quebec, Canada. The establishment of peatlands started about 6000-5000 yr B.P.. The vegetation cover developed from rich fen communities, to poor fen, to bog and to frozen bog communities. The ombrotrophication was favored by late Holocene cooling and by the high peat accumulation. A comparison of the Late-Holocene development of studied peatlands located in the same region suggests that permafrost initiation was due to cool and dry climate rather than the existence of Sphagnum-peat cap. However, Sphagnum cover prevented the permafrost from melting. The collapse of palsas (permafrost degradation) is a consequence of increasing temperatures and precipitation since the end of the Little Ice Age. Macrofossil results of the filled thermokarst ponds show that the vegetational succession was driven by three bryophyte assemblages: Calliergon giganteum and Sphagnum riparium when the pond's depth was at a maximum, S. riparium and C. giganteum when the pond was partly filled in, and S. lindbergii and S. riparium since the pond was completely filled in.

09 Feb. Margaret Carreiro, Department of Biology, University of Louisville.
"A tale of two cities: soil carbon and nitrogen cycling in oak forests along urban-rural gradients in New York City and Louisville, Kentucky."

Both because of their typically smaller size and greater edge-to-interior ratios and because of a highly contrasting matrix type, urban and suburban forests, as opposed to rural forests, are likely to be disproportionately affected by their external surroundings. Compared with forests in rural areas, these urban forest remnants would likely be subjected to greater external inputs of thermal energy, greater atmospheric inputs of both injurious pollutants and fertilizing nutrients, increased colonization by exotic species, and increased human visitation. This talk will focus on the variation in decomposer communities and other factors affecting soil carbon and nitrogen cycling in oak forests along an urban-to-rural land use gradient in New York City (population 8 million). Recent establishment of another gradient of oak forest sites in and near Louisville, Kentucky (population 700,000) has allowed us to determine whether any patterns observed in New York City area forests also exist in forests within and near a smaller city. Such intercity comparisons can help us start to determine which natural population, community and ecosystem level responses in natural habitat remnants are shared across cities in different regions or biomes, what the thresholds for such responses are in relation to the magnitude of particular urban factors, which natural communities and ecosystem processes are more sensitive to urban impacts than others, and which responses or patterns may be idiosyncratic to specific cities.

12 Jan. Cindy Nevison, National Center for Atmospheric Research (NCAR). "Stratospheric influence on the tropospheric seasonal cycles of Nitrous Oxide and CFCs 11 and 12: Implications for N2O and O2 budget studies."

The stratospheric influence on the tropospheric seasonal cycles of N2O, CFC11, and CFC12 is investigated using observations from global trace gas monitoring networks and the NCAR Whole-Atmosphere Community Climate Model (WACCM). WACCM makes a number of theoretical predictions about the impact of the stratospheric meridional downwelling circulation on trace species like N2O and the CFCs, whose primary sinks are in the stratosphere. These predictions are generally consistent with observations, suggesting that the stratosphere does exert a coherent influence on tropospheric seasonal cycles. The stratospheric influence may potentially confound efforts to validate estimated source distributions of N2O, an important greenhouse gas, in atmospheric transport model (ATM) studies. A method is suggested for correcting observed N2O data for stratospheric influences using CFC12 observations and a model-derived N2O:CFC12 scaling factor. This method is applied in a study of N2O and O2 ventilation from the Southern Ocean using data from the Cape Grim, Tasmania monitoring station.

01 Dec. James McGoodwin, Anthropology Department, University of Colorado at Boulder (and INSTAAR affiliate).
" Climatic variability and Yup'ik Eskimo subsistence strategies."

Professor McGoodwin discusses research exploring how climatic variability influences the subsistence strategies of Yup'ik Eskimo in Southwest Alaska. While most ethnographies describe their subsistence economies as a virtually immutable round of certain activities during certain seasons, in fact climatic variability prompts considerable variability in their subsistence-activity strategizing from one season to the next. Complicating the research is the fact that climatic variation is not the only factor influencing Yup'ik subsistence strategies as other factors often also play an important role, for example: changing relationships among dissimilar Yup'ik communities; changing relationships with various governing bodies; wage-labor opportunities in the region and beyond; desires to develop "eco-tourism" that capitalizes on traditional subsistence activities; and local-level impacts of global cultural and economic phenomena. Overall, better understanding how the Yup'ik adapt their subsistence strategies to contemporary climatic variation may help with forecasting how they may (or may not) be able to adapt to longer-term and more extreme climatic and global changes in the future.

24 Nov. Bruce Hungate, Northern Arizona University.
"Element cycling in response to atmospheric change: ecosystem impacts, global feedbacks."

Global atmospheric change can alter ecosystem processes, and the changes in ecosystem processes themselves can feed back to the atmosphere, modulating the pace of continued atmospheric change. Rising atmospheric CO2 could alter water cycling, for example, by decreasing stomatal conductance. This response extrapolated globally in climate models could amplify global warming. Similarly, the effects of elevated CO2 on nitrogen cycling will likely influence the size and persistence of the terrestrial carbon sink, in turn affecting the trajectory of future atmospheric CO2 rise. In this seminar, I will discuss the effects of increasing atmospheric CO2 on the water, nitrogen, and carbon cycles in terrestrial ecosystems, and how these effects might feed back to atmospheric CO2. I will present empirical results from work conducted at the ecosystem scale, and explore their implications for global projections of future carbon storage by the terrestrial biosphere.

17 Nov. Jason Neff, Geological Sciences, University of Colorado at Boulder. "Blowing in the wind: The biogeochemical implications of dust deposition and wind erosion in southwestern US ecosystems."

Dust is a common feature of arid Western US landscapes and plays important roles in both nutrient inputs and loss from terrestrial ecosystems. Dust is comprised of small particles of minerals lofted into the atmosphere, and then carried for tens to thousands of kilometers. Typically dust contains silt and clay size particles that are relatively enriched in nutrients (particularly base cations and P). When this dust is deposited into ecosystems, it can contribute a significant amount of soil and rock-derived nutrients to soils. In the Canyonlands region of SE Utah, the magnetic properties (isothermal remnant magnetism and magnetic susceptibility) of far-traveled eolian dust can be used to track the accumulation of soil mass and nutrients in undisturbed ecosystems. In stable environments where there has been little surface disturbance, our results indicate that dust accumulation is more important than bedrock weathering for the delivery of base cations and P to soils. Livestock grazing, however, can reverse this process through rapid and widespread disturbance of soil surfaces. Following grazing, there are substantial losses of soil fine particles to wind and water erosion of soils, leading to large reductions in soil nutrient content. Surface recovery in these ecosystems is slow and our results suggest that impacts on nutrient loss can persist for multiple decades after grazing ends.

10 Nov. Steve Schmidt, Ecology & Evolutionary Biology, University of Colorado at Boulder.
" Thriving microbial life beneath winter snow packs and alpine glaciers: Novel organisms and biogeochemical implications".

Steve will review his lab's recent work exploring the under-snow world of alpine environments in Colorado and some high elevation (5000 m+) glaciers in the Peruvian Andes. Surprisingly, there are very active microbial communities functioning in both of these environments. Steve will discuss the weird and wonderful new organisms they have discovered and the implications of their activities for nitrogen, carbon and phosphorus cycling in cold ecosystems. This work was recently highlighted in the journal Science, and received nation-wide run in the press. Join us at the seminar to learn why!

20 Oct. John Miller, National Oceanic and Atmospheric Administration (NOAA).
"What a decade of global atmospheric 13-CO2 measurements tells us about the oceans and biosphere.

Since 1990, INSTAAR's Stable Isotope Lab has made close to 100,000 13CO2 measurements on air samples NOAA/CMDL's global sampling network. The signals in the data reflect the influence of both terrestrial and oceanic carbon fluxes, and our main objective in interpreting the data has been to derive these fluxes as a function of space and time. The dominant signal in the data is a persistent uptake of carbon in the temperate Northern Hemisphere. The other major signals are enhanced terrestrial uptake associated with the eruption of Mt. Pinatubo in 1991, and an enormous release of carbon from the tropical biosphere during 1998. Additionally, we observe large isotopic signals in both the tropics and temperate latitudes that have no obvious climatic drivers.
There are other ways besides 13CO2 measurements to estimate terrestrial and oceanic fluxes. We can use these independent flux estimates to solve for parameters in the atmospheric 13CO2 budget related to the residence time of carbon in the biosphere and oceans. We will look at the calculated values of these parameters to see what they say about both our original parameter estimates and the validity of the independent flux estimates.

13 Oct. Jill Baron, Natural Resource Ecology Laboratory (NREL), Colorado State University.
"Land use change and nitrogen emissions along the Colorado Front Range."

The Colorado Front Range, home to 68% of Colorado's residents, is a region that has experienced rapid population growth and land use change over the past several decades. Coincident land conversion from agricultural and non-federal forest lands has resulted in the growth of urban, suburban, and exurban land area. In addition to urban sprawl, there have been large changes in agricultural practices and land use in this region. Among the consequences of human population growth and agricultural intensification is an increase in reactive nitrogen (N). Food and energy production, and transportation byproducts produce reactive nitrogen species, NOx and NH3. Increased atmospheric deposition of NOy and NHx can lead to enrichment and acidification of terrestrial and aquatic communities, and adverse effects on human health. Atmospheric N deposition to high mountain ecosystems along the Colorado Front Range has affected both aquatic algal communities and increased soil N cycling. We trace here the history of land use in a rapidly changing region and describe how these alter NOx and NH3 emissions.

06 Oct. Gaute Mikalsen, Department of Geology, University of Tromsø, Norway.
"High resolution oxygen isotope records from North Norwegian fjords and shelf, reflecting past and recent oceanographic changes in the Norwegian Current."

The aim of this study is to: 1) Prolong the existing instrumental temperature records further back in time (Existing fjord records go back to c. AD 1933), with as high resolution as possible. 2) Evaluate how well we are able to reconstruct the past temperatures.
     Sediment cores from North Norwegian fjords and shelf have been investigated using stable oxygen isotopes on foraminifera. The cores were cut in to 3mm slices that gave resolution of c. 1 year per sample for the last 100 years and 2 to 5 years per sample before AD 1900. The calculated temperatures from the oxygen isotope record correlate well with 20 to 100 year instrumental temperatures records at the core locations and at nearby oceanic stations. There is a good correlation between the temperature records from the fjords and records temperature records from the Norwegian Current (NC). These correlations indicate that the changes seen in the oxygen isotope records from the fjords are a result of temperature changes in the NC. There is also a good correlation to coastal air temperatures indicating a regional climate signal. The oxygen isotope records prolong the existing instrumental temperature record further back in time, providing longer records to investigate the causes of temperature change in the NC, which is an important transporter of heat to high latitudes and the arctic. Forcing mechanisms such as NAO, solar irradiance and volcanism are investigated.
     The records show that the end of Little Ice Age was as late as in the beginning of the 20th century in the temperatures of the NC. There was a cooling from c. AD 1950 to 1980 that is also recorded in the instrumental temperature series and an increase in temperatures the last 20 years is also recorded. The temperature increase is c. 0.5ÁC the last 100 years.
     By investigating such high resolution records some questions regarding the methods that have only been of minor interest for records with lower resolution, has got high priority. These include:
1). What time of the year do foraminifera make there test?
a) Is this at the same time every year?
b) Do different foraminiferal species make there test at different time of the year?
2). How well are we able to date high resolution marine records that are not yearly laminated?
a) Are there methods that may improve the age control?

29 Sep. Mervi Hjelmroos-Koski, School of Public Health, University of California, Berkeley.
"Worldwide travelers without a passport."

Most pollen grains are deposited within few hundred meters of their source. Under certain meteorological conditions biological material is injected higher into the atmosphere where it can be transported across continents and seas at distances of thousands of kilometers. Downward air movements associated with condensation and precipitation will re-deposit the pollen grains with other transported material.
Pollen grains can be carried on larger particles, and the pollen grain itself acts as a transport surface for smaller particles and aerosols. Measured with a continuous volumetric air sampler, not only the concentration but also the time, within a 30-minute window, for the deposition can be calculated. By identifying areas of potential vegetation sources, transported biological material, weather conditions, and air mass pathways, the origin for long distance depositions is determined.

22 Sep. Tom Marchitto, INSTAAR.
"Atlantic-Pacific climate teleconnections at millennial time scales."

The climate of the Northern Hemisphere during the last glaciation was dominated by so-called Dansgaard/Oeschger cycles, which are rapid, large magnitude climate swings first identified in Greenland ice cores. These cycles have recently been found in a number of tropical and subtropical records, indicating the existence of long-range climate teleconnections that are poorly understood. Organic matter concentrations in a sediment core from the oxygen minimum zone (OMZ) off southern Baja California (705 m water depth) vary in concert with Dansgaard/Oeschger oscillations. A measure of sediment color (the third principal component of the diffuse spectral reflectance) displays a particularly striking similarity to Greenland ice core temperature records over the past 50 kyr. High organic matter concentrations during interstadials and during the Holocene may have been caused by increased productivity and/or increased preservation due to reduced OMZ ventilation. Changes in ventilation could have been caused by competition between warm, salty, low-oxygen (tropical) intermediate waters and cool, fresh, high-oxygen (North Pacific) intermediate waters. Temperatures derived from benthic foraminiferal Mg/Ca are inconsistent with this ventilation scenario, however. Rather, we believe that productivity has been the dominant control on organic matter accumulation and northeastern Pacific OMZ strength. Modern productivity in this region is controlled by ENSO dynamics, and we suggest that a North Atlantic-Asian monsoon-ENSO linkage might explain the observed hemispheric distribution of Dansgaard/Oeschger variability.

15 Sep. Carrie Morrill, Advanced Study Program & Climate and Global Dynamics Division, National Center for Atmospheric Research (NCAR).
" Holocene variations in Asian monsoon precipitation: Links to solar forcing and high latitudes."

The Asian summer monsoon is one of the most important phenomena in the Earth's climate system. Monsoon extremes cause flooding and droughts that impact more than a third of the world's population. In addition, the Asian monsoon may affect climate globally, through interactions with El Nino and mid-latitude circulation. Despite the importance of the monsoon, there are few records of past variations in its strength. I will present (1) a new record of monsoon precipitation variations inferred from the geochemistry of lake sediments in central Tibet and (2) a compilation of previously-published monsoon records that is designed to identify the timing and spatial extent of abrupt changes in precipitation. A combination of solar and internal climate system forcing appears to be responsible for the monsoon variations. Results suggest that strong connections between high and low latitudes, as documented for the last glacial period, also existed through the Holocene.

25 Aug. Jonathon A. Warrick, Coastal and Marine Geology, US Geological Survey, Menlo Park.
" Land sources and ocean dispersal of river sediment in southern California."

The active tectonics and semiarid climate of southern California has produced rivers that discharge sediment at very high yields, albeit only during large, winter events. During the past 60 years, many of the lowlands of the region have been urbanized to facilitate excessive rates of population increase, which has dramatically altered the region’s hydrology. Here I will show three examples of how the geology, climate and land use of southern California control river sediment production and dispersal into the ocean. First, the western, Transverse Ranges are understood to be the fastest eroding region of southern California (Inman and Jenkins, 1999). Using event based sampling and historic USGS data, I show that these high rates of denudation are largely a function of localized areas with exceptional erosion due to high rates of uplift, weak geology, and landsliding. Second, river sediment loads from the urbanized watersheds have been difficult to calculate due to high scatter in the sediment rating curves (e.g., Brownlie and Taylor, 1981). Here we show that scatter in the Santa Ana River rating curves can be explained by order of magnitude decreases in suspended sediment concentrations over a 35 year period. These decreases occur coincidentally to steady increases in stormwater runoff, which are associated with increases in urban impervious surfaces throughout the watershed. Total sediment flux is shown to be steady over this time with respect to other, non-urbanizing watersheds, which is counter to the classic understanding of decreasing rating curves. Finally, density relationships during large hydrologic events suggest that river dispersal to the ocean is hyperpycnal (negatively buoyant). We hypothesize that these hyperpycnal events transport littoral materials offshore of the region’s beaches, potentially impacting these littoral sediment budgets (Warrick and Milliman, in press).

12 May Snehalata Huzurbazar, Department of Statistics, University of Wyoming, "An Overview of statistical methods: what statistics can and cannot do."
Statistical methods are often misused, misunderstood and also underutilized. There are a variety of reasons for this. For instance, researchers are introduced to basic methods through one or two statistics courses, resulting in a fairly incomplete view of the possible applications of statistics. Also, communication between statisticians and other researchers can be difficult. I will be spending my sabbatical during 2003-4 at INSTAAR, and as a means of introducing my research, I will provide an informal overview of statistical methodology. My aim is to also provide some insight into how statisticians view data analysis, and to emphasize the possibilities and the limitations of the use of statistics, using examples from my research.

08 May     Wes LeMasurier, Department of Geology at CU Denver, "Cenozoic reactivation of the West Antarctic Rift System in Marie Byrd Land."
     The Marie Byrd Land (MBL) tectonomagmatic dome is a reactivated portion of the West Antarctic rift system that has undergone uplift and contemporaneous volcanism since early Oligocene time. It occupies an area of about 800x500 km on the MBL coast. Uplift and basalt magmatism began about 37-34 Ma in eastern MBL, but the center of uplift shifted ~470 km westward to the present crest of the dome (Mount Petras) around 29-25 Ma. Since then, there has been ~3 km of dome uplift accompanied by sometimes voluminous basalt volcanism and the development of horst and graben structure. Felsic volcanism began ~19 Ma with the growth of Mount Flint volcano, near the crest of the dome, and has accompanied basalt volcanism and dome uplift ever since. There are 17 other felsic volcanoes in the province, and they become systematically younger toward the distal flanks of the dome, where all the presently active volcanoes are found.
     The volume of volcanic products and magnitude of fault offset have been difficult to estimate. IGY-related oversnow traverses provided the first and only seismic data for this entire region. A seismic line across the east end of Toney Mountain shows a contact between Cenozoic basalt and basement rock at a depth of 3 km below sea level, or ~5 km below the exposed top of the basalt section. This single line provides the only data on the magnitude of fault offset in this region (~4 km), and the most direct evidence that the MBL province may be a large igneous province (LIP). Less direct evidence for the latter comes from attempts to model the amount of basalt required to produce the large volumes of felsic rock found in the 18 felsic volcanoes. However, no realistic estimate of the volume of volcanic products can be made without additional seismic data.
     Estimates of crustal thickness in coastal MBL have been based on models of gravity data and on surface wave dispersion studies, neither of which resolves questions about the origin of dome uplift. Mantle plume activity has been proposed to explain the coincidence of uplift and basalt volcanism, and this seems to be compatible with available gravity data. However, seismic determinations of crustal thickness and upper mantle velocity are needed to test this proposal, and to answer other petrologic and tectonic questions. Is, for example, the dome supported by thick crust or low-density mantle (Airy vs. Pratt compensation, or a combination of both)? If plume activity can be confirmed, and if plume activity has supplied the suspected large volume of new igneous material over the past 37-34 m.y., has the crust been correspondingly thickened, or has extension compensated for the addition of new material? Seismic imaging of the faults is also relevant to the question of extension, by determining if they flatten with depth or are high angle and planar.

28 Apr.     Larry Benson, U.S. Geological Survey, Denver Federal Center, "Cosmogenic dating of Pre-Pinedale, Pinedale, and Post-Pinedale moraines in North Central and Southwestern Colorado."
     Eight Pinedale boulders from north-central Colorado moraines and 14 Pinedale boulders from southwestern Colorado moraines have 36Cl ages ranging from 16.5 to 21.5 kyr. 10Be age determinations on four boulders from north-central Colorado are in close agreement with 36Cl determinations on the same boulders. The Colorado Pinedale boulder ages are consistent with 10Be ages obtained by John Gosse from Pinedale moraines in the Wind River Range of Wyoming. Corrections combining surface erosion rates and snow shielding suggest that Colorado Pinedale boulders are up to 3000 yr older than their apparent 36Cl ages, making difficult comparison of Pinedale advances and retreats with North Atlantic millennial-scale climate records.
     Most ages for pre-Pinedale (Bull Lake) boulders fall within marine-isotope stage (MIS) 5, a time when continental and Sierran ice accumulations were small or nonexistent. Under the assumption that the pre-Pinedale boulders were deposited during MIS 6 (at ~140 kyr B.P.), calculations indicate that rock-surface erosion rates would have had to range from 5.9 to 10.7 mm kyr-1 to produce the observed 36Cl values. These erosion rates are extremely rapid (10 to 20 times greater than post-Pinedale rates) and were probably not achieved. Snow shielding may account for 0 to 48% of the additional years needed to shift pre-Pinedale dates to MIS 6. This suggests that sediment shielding or 36Cl leaching has greatly decreased the apparent ages of some pre-Pinedale boulders. Boulders from loop moraines deposited in the Butler Gulch and Chicago Lakes areas of the Front Range indicate at least two different periods of post-Pinedale moraine formation. The older of these two advances, documented at Chicago Lakes, appears to be equivalent to the Wind River Titcomb Lakes (Younger Dryas) advance documented by John Gosse. The younger Butler Gulch advance has a relatively wide range of boulder ages, indicating that erosion during boulder transport did not fully erase cosmogenic inheritance. A method for inheritance correction of the subangular Butler Gulch boulders will be discussed.

21 Apr. Irina Overeem, INSTAAR, "Quantifying stratigraphic variability; a case-study of the New Jersey shelf over the last 21,000 years."
This talk presents a numerical modeling study using the New Jersey shelf development since the Last Glacial Maximum as an example. HydroTrend and SedFlux are run to mimick the rather complex history of the shelf, where rapid sea level rise, glacial melting and climate change interact. We set up a best-guess scenario and compared the simulated stratigraphy against available seismic data and found a reasonable match. Subsequently, the ranges in key climatological boundary conditions and their effect on the stratigraphy predictions have been evaluated. It was found that the dynamics of the Laurentide Ice Sheet control the drainage area of the rivers draining towards the NJ shelf and as such form an important control on discharge and sediment supply variability and consequently on the depositional geometry. Temperature and precipitation scenarios were based on CCM model output. Considerable variability especially as a result of changing precipitation conditions, is associated with these apparently sophisticated inputs. Even more uncertain is the effect of changing storm conditions, both due to limited data input as well as a more primitive process description. Uncertainty in long-term climatological boundary conditions certainly affects our ability to make quantitative stratigraphic predictions. But carefull mapping of the effects of the uncertainty provides an associated variability attribute that makes the model prediction more valuable.

07 Apr. Stephen J. Mojzsis, Department of Geological Sciences and NASA Center for Astrobiology, Univ. of Colorado at Boulder, "Investigating early terrestrial atmospheres and biospheres in the chemistry of sulfur isotopes."
I report sulfur isotope anomalies with D33S, the deviation from a mass-dependent fractionation line for the 3-isotope system (34S/32S vs. 33S/32S), ranging up to ± 2 per mil within individual Archean (pre-2.5 billion year old) sedimentary sulfides from a variety of localities. The measurements, which are made in situ using multicollector secondary ion mass spectrometry, unequivocally corroborate prior bulk measurements of mass-independent fractionations (MIF) in sulfur by Farquhar and coworkers (2000) and provide additional evidence for an anoxic atmosphere on the Earth before ~2 Ga. This technique also offers new opportunities for exploring ancient sulfur metabolisms preserved in the rock record. The presence of MIF sulfur in sulfides from a >3.8 Ga Fe-rich quartzite from Akilia (island), West Greenland is consistent with a marine sedimentary origin for this rock.

31 Mar. Eric Leonard, Colorado College, Geology Department, "Neogene tectonic uplift, erosion and isostasy on the Colorado Piedmont."
The Colorado piedmont region was tilted and broadly warped during the Late Cenozoic. This deformation involved a complex interplay of tectonic forcing, river erosion, and isostatic response to erosion. Modeled erosional isostasy closely replicates the observed pattern of deformation, but accounts for only about half its magnitude. The remainder reflects tectonic rock uplift that increases southward across the piedmont, likely reflecting proximity to the northward-propagating Rio Grande Rift. This differential uplift triggered differential erosion, concentrated on southern piedmont river systems, particularly the Arkansas River. Differential erosion led in turn to differential isostatic rock uplift focused on the Arkansas drainage. Covariation of tectonic uplift, erosion, and isostatic compensation across the piedmont reflects a strong positive feedback between uplift-induced erosion and erosion-induced isostasy, which has progressed to the point that isostatic uplift is approximately equal to the initial tectonic forcing.

03 Mar. Jerry Peterson, Assoc. Vice Chancellor for Research, Univ. of Colorado at Boulder, "'Cosmic rays and errors in computer memory chips."
Cosmic rays bombard us and our computer chips all the time. Computer memory chips can be sensitive to very small amounts of charge deposited by reactions from cosmic rays, and this charge can cause Soft Error Upsets, changing a bit but not otherwise damaging the machine. The wrong information caused by this SEU can crash your system. The talk will describe these processes, show how we measure the rates in the laboratory, and indicate the sensitivities of various memory chip styles. The particular example will be an unfortunate decision made by Sun Microsystems in their choice of DRAMs.

10 Feb.     Gene Wahl, Environmental and Societal Impacts Group, National Center for Atmospheric Research (NCAR), "Quantitative climate interpretation from pollen, and data-model comparisons."
     In the first part, Dr. Wahl will present methods he has developed for determining threshold values to use in the MAT, in terms of optimally distinguishing pollen samples from like and non-like vegetation and in terms of optimizing climate reconstructions. The methods used for distinguishing pollen from like and non-like vegetation are closely related to “Receiver Operating Characteristic” analysis, first developed in signal detection theory and later becoming heavily used in medical test analysis and weather prediction skill analysis.
      In the second part, Dr. Wahl will present methods and results from Monte Carlo analyses he has developed in collaboration with Dr. David Lytle (USFS). These tools have been used to examine how thresholds and reconstruction rules employed in the MAT interact with count sizes of pollen samples, in order to rigorously examine how to apportion counting effort (a significant efficiency issue in pollen-based paleoclimatology and paleoecology). The results contain significant surprises that contravene some of the conventional wisdom on the way counting and analytical effort should be apportioned. The techniques presented are generally applicable to the use of the MAT with other paleo-reconstruction indicators, e.g., sediment diatom archives employed for reconstructing paleolimnological chemistry and hydrology.

03 Feb. Detlev Helmig, INSTAAR and Program in Atmospheric and Oceanic Sciences (PAOS), "New insights into snow-photochemical processes and snow-atmosphere gas exchange (if you ever wonder what may happen in your freezer if the light stays on)."
Snowpack has been considered a rather inert substrate that undergoes little chemical interaction with the atmosphere. The conservation of gases in interstitial air and ice cores has been used to decipher records of past atmospheric composition and climate. Over the past decade an increasing number of previously unknown snow-photochemical reactions have been discovered. These processes have been shown to affect the surface-atmosphere exchange of many trace gases and may have implications on the interpretation of ice core records.

27 Jan. Russ Graham, Denver Museum of Nature and Science, “The Colorado Ice Bison and biogeography of late Quaternary Bison in North America."
The Ice Bison was discovered on Jones Pass at about 13,000 feet above msl by an amateur archaeologist in August 2001. While hiking the Continental Divide Trail, Ed Knapp observed the back part of a bison skull melting out of a snow and ice field along the trail. Ed had hiked this area for over 20 years and this is the most melting that he had ever noticed. Upon closer investigation, he noticed that other bones were also melting out of the snow. Because he was afraid that some one might collect the skull as a trophy and because Ed knew that Bison did not normally occur at that elevation, he collected the skull and brought it to the Denver Museum of Science & Nature. Dave Baysinger, DMNS photographer, Ed and I then visited the site in September of 2001. More ice had melted exposing other bones that we systematically collected. We returned in August, 2002, to collect more specimens after the ice had completely melted. A radiocarbon date of 340 +/- 40 years BP on the skull indicated that the Ice Bison had died during the Little Ice Age. Because the bones are not heavily weathered, it appears that this may be the most significant melting of this ice field in the last 400 years and that it is consistent with current trends in warming temperatures at high elevations and latitudes. Finally, in the context of late Quaternary Bison biogeography, this specimen and others from the mountains raise interesting questions about an alpine bison phenon.

11 Nov. Joe Stoner, INSTAAR, "Holocene paleomagnetism in the Arctic: New frontiers in geophysics and chronostratigraphy."
Quaternary paleomagnetism and geomagnetism is undergoing a renaissance. Our knowledge of the spatial and temporal variability of the geomagnetic field is improving at a rapid rate as data is finally beginning to out run speculation. Much of this growing new understanding is fueled by the availability of new instruments that allow rapid measurements of sediment sequences providing new observational constraints from previously untapped archives. Additionally, both numerical geodynamo and data based spherical harmonic models are making substantial progress. The new understanding of the geomagnetic field that is beginning to emerge provides a new set of tools by which paleomagnetic record can be used to study the Quaternary Earth. In this presentation I intend to outline the present state of Quaternary Paleomagnetism and take a look at what may be unique about the Arctic. I will present new Arctic paleomagnetic data from Ellesmere and Devon Island lakes and outline a new proposal intended to start to fill a significant data gap that presently exists in high latitude regions. The ultimate goals of this study are to provide a Holocene chronostratigraphic-dating tool for the Arctic and new fundamental observation on the nature of the geomagnetic field.

01 Nov. Steve Goodbred, State University of New York, Stony Brook, "The Ganges-Brahmaputra sediment dispersal system: Controls, responses, and stratigraphy during the Late Quaternary."
Rivers are the main source of terrigenous sediment delivered to continental margins and thus exert a major control on coastal evolution and sequence development. However, little is known about past changes in fluvial sediment loads despite the recognition of significant variation under changing climatic regimes. In this study we present the first quantified estimate of sediment discharge for a major river system under conditions of an intensified early Holocene monsoon. Development of the Ganges-Brahmaputra River delta began ca. 11 000 yr B.P., when rising sea level flooded the Bengal basin, thereby trapping most of the river’s discharge on the inner margin. Chronostratigraphic data from these deltaic deposits are used to calculate the rates of sediment storage on the margin, which provide a minimum estimate of the river’s past sediment load. Results reveal that ~5 × 1012m3 of sediment was stored in the Bengal basin from ca. 11 000 to 7000 yr B.P., which corresponds to a mean load of 2.3 × 109 t/yr. In comparison, modern sediment load of the Ganges-Brahmaputra is ~1 × 109 t/yr, ranking it first among the world’s rivers and underscoring the significance of a two-fold increase sustained over 4 k.y. Furthermore, the timing of immense discharge in the early Holocene strongly suggests its relation to a stronger than present southwest monsoon in South Asia. Similar patterns of high monsoon-related sediment discharge have been noted throughout the tropics and subtropics, suggesting a widespread fluviosedimentary response, the potential magnitude of which is showcased by the Ganges-Brahmaputra system.

23 Sep. Donna Francis, Harvard University, "Chironomids as indicators of past climate change in the Arctic."
Remains of chironomid larvae that accumulate in lake sediments over time represent an increasing valuable proxy in the study of past environments and climate. Inference models are being developed from modern training sets to quantify paleotemperatures based on changes in faunal assemblages over time. I will talk about our results from lakes on Baffin Island and southern Greenland. In addition to using change in species over time to infer past water temperatures, we are developing a new technique using oxygen isotopes in the chironomid head capsules as a temperature proxy. Our preliminary results from sediment cores and a transect of modern samples are extremely promising and show that d18O measured in chironomid head capsules is a reliable proxy for lakewater d18O and temperature.

Spring 2002

Apr. 22 John Hoffecker, INSTAAR, "The Last Glacial Maximum and the peopling of the New World."
The initial peopling of the New World was tied to the ability of modern humans to occupy environments above latitude 60d North (which coincides with the southern margin of Beringia). With isolated and problematic exceptions, this ability does not seem to have developed until after the peak of the Last Glacial Maximum (20,000-18,000 yrs BP). The critical factor may have been the morphology of the modern human population of northern Eurasia, which retained an extreme warm-climate appearance until that time (reflecting lower latitude origins). U.S. Army medical research indicates that modern people with similar morphology will experience high rates of cold injury in subarctic and arctic climates despite use of insulated clothing. After 18,000 yrs BP, modern humans in northern Eurasia exhibit morphological adaptations to cold (e.g., reduced limb dimensions) and begin to occupy higher latitudes, eventually including Beringia. Although other factors probably constrained the settlement of Beringia and the New World during 18,000-12,000 yrs BP (e.g., glaciers), modern human morphology may have been critical to the process and may account for the absence of people in the western hemisphere prior to the Last Glacial Maximum.

Apr. 15 Lothar Schrott, INSTAAR visiting scientist, Department of Geography, University of Bonn, "Sediment storage in alpine catchments: Quantification and variability."
Spatial patterns of sediment storage types and associated volumes using a novel approach for quantifying valley fill deposits are presented for alpine catchments in the Bavarian Alps/Germany and in the Dolomites/Italy. The different sediment storage types were analysed with respect to geomorphic coupling and sediment flux activity. Spatial information of storage types was based on geomorphological mapping, airphoto-interpretation and GIS-analysis. The most dominant landforms in the valley of the Bavarian Alps terms of surface area were found to be talus slopes (sheets and cones) followed by rockfall deposits and alluvial fans and plains. More than two thirds of the talus slopes are relict landforms, completely decoupled from the geomorphic system. Notable sediment transport is limited to avalanche tracks, debris flows and along floodplains. Temporal information was derived from concepts on paraglacial slope adjustments, surface activity and dating results obtained from two 12 and 5.5 m drilling cores. Sediment volumes were calculated by means of polynomial functions of cross-sections and GIS modelling. In addition, 66 seismic refraction profiles were carried out throughout the valley for a more precise determination of sediment thicknesses, and to check the bedrock data generated from geomorphometric analysis. The seismic refraction data showed that large floodplains and sedimentation areas, which have been developed through damming effects from large rockfalls, are in general characterised by shallow sediment thicknesses (< 20 m). By contrast, the thickness of several talus slopes is more than twice as much. For some locations (e.g. narrow sections of valley) the polynomial generated cross-sections resulted in overestimations of up to one order of magnitude, whereas in sections with a moderate valley shape the modelled cross-sections are in good accordance with the obtained seismic data. For the quantification of valley fill deposits a combined application of bedrock data derived from polynomials and geophysical prospecting is highly recommended.

Apr. 08   Ned Andrews,USGS, "Influence of ENSO on flood frequency along the California Coast."
     E.D. ANDREWS (1), RONALD C. ANTWEILER (1), PAUL J. NEIMAN (2), F. MARTIN RALPH (2) (1) U.S. Geological Survey/WRD, 3215 Marine St., Ste E127, Boulder, CO 80303 (2) NOAA/Environmental Technology Laboratory, Boulder, CO 80305
     The influence of the El Niño/Southern Oscillation (ENSO) phenomena on flooding in California coastal streams is investigated by analyzing the annual peak floods, Q(subscript: pk) , recorded at 38 gaging stations. The state of ENSO prior to and during flooding is characterized by the multivariate ENSO index (MEI) where MEI < - 0.5 is La Niña and MEI > 0.5 is El Niño. The flood magnitude, as represented by log Q(subscript: pk) in all 20 streams located south of 35° N has a significant positive correlation, (r = 0.3 ? 0.6) whereas in 3 of the 4 streams located north of 41° N flood magnitude has a significant, negative correlation with increasing MEI from ? 2.2 to increasing + 3.2. Correlations are uniformly weak and insignificant, however, when the floods are subdivided into El Niño, neutral and La Niña periods. South of 35° N, El Niño floods are significantly larger than non-El Niño floods. The mean log Q(subscript: pk) (El Niño) is 2-16 times the mean log Q(subscript: pk) (non-El Niño). During an El Niño, however, the relative strength of the El Niño has, at most, a weak influence on flood magnitude. Flood exceedance probabilities for the El Niño and non-El Niño period were calculated for all gaging stations using the log ? Pierson Type III distribution. For exceedance probabilities from pe = 0.50 ? 0.02, the ratio of the El Niño to non-El Niño floods varies from greater than 10 near 32° N to less than 0.7 near 42° N. Latitude explains 76 to 90 percent of the observed variation in the relative magnitude of El Niño versus non-El Niño floods over the range of exceedance probabilities.

Apr. 01 Chris Jenkins, INSTAAR, "A global GIS of seabed materials".
With a range of software tools like those of AI, miscellaneous datasets from decades of seabed sampling can be brought into conformance and can be mapped as one. This project, dbSEABED*, has over 600,000 sample sites contributing to maps, grids, etc. that map seabed roughness, river outfalls, chemical and biofacies, glacial deposits and many other attributes. Outputs of the project have many applications, and they are being supplied now to numerical modelers (eg. carbon sinks), decision makers (whale comms), engineers (pipelines) and researchers (ocean nutrients). Global and polar examples of the mappings will be shown. *dbSEABED is collaborative with NGDC and USGS.

Mar. 11 Michael Richter, Inst. of Geography Univ. Erlangen / Germany, "Hygro-climatic interpretation by phytoindication in high mountains."
     Although considered water towers for their forelands mountain ranges are missing appropriate climate data due to insufficient nets of weather stations. Vegetation, i.e. degree of coverage, growth forms, and associations can deliver detailed information for an estimation of the amount of humid months at any mountain site.
     The author developed various methods of hygro-climatic phytoindication adapted to high mountains (1) Examples from mountain chains surrounding the Central Asian Taklamakan (southern Tian Shan, eastern Pamir, western Kunlun) basing on floristic similarity analyses of south and north-exposed valley slopes give hints on regional circulation patterns. (2) In the perarid high Atacama of northern Chile checking plant coverage exhibits best results to show up the influence of mass elevation or of the „Merriam-Effect‰ on hygric regimes. (3) Within humid neotropical mountain regions leaf-size analyses of Melastomataceae are adequate for fine-tuned judgement of the number of humid months of smaller areas (i.e. valley transect with adjacent slopes = mesoclimate), exemplified by results from Zongo Valley (Bolivia) and the Sierra Madre de Chiapas (Mexico). (4) However, in the tropics similarity analyses by epiphytism on solitary trees are of best profit for the investigation of hygric conditions of a region with complex climatic structure (i.e. valleys, escarpments, and mountain ranges = macroclimate). The presentation points out results of similarity analyses based on 140 relevés in southern Ecuador (Nudo de Loja = hot spot of diversity) to complete a hygro-climatic map which for its part allows the completion of maps of natural vegetation and of regional circulation patterns.
     The methods, feasible also for non-botanists, are of practical use providing basic information for agricultural planning since risks and profits can be derived.

Feb. 25   Wes Lemasurier, Department of Geology, Univ. of Colorado at Denver, INSTAAR Affiliate," A 35 M.Y. history of uplift and erosion of the Marie Byrd Land Dome: Implications regarding glacial history and possible Mid-Cenozoic plate motion in West Antarctica"
     Throughout the past 25 m.y., alkaline volcanism along the Pacific coast of Marie Byrd Land has been accompanied by the uplift of a broad dome, which now stands nearly 3 km above sea level and is roughly 700 km across. The dome crest is the central point of two spatial and temporal patterns of volcanic activity that provide a means of estimating the rate and timing of dome uplift. Both uplift and volcanism have been interpreted to be the product of mantle plume activity beneath a stationary plate, which is consistent with what we know about the tectonic environment of West Antarctica since ~25 Ma.
     Erosion in this polar environment has not kept pace with dome uplift over the past 25 m.y., even though the estimated rate of uplift of ~100m/m.y. is exceedingly slow. Topography still clearly reflects the magnitude and sense of structural displacements. For example, the very low relief West Antarctic erosion surface, of Late Cretaceous age, is preserved at the crest of the dome, 2700m above sea level, where it is overlain by weakly indurated ~25 Ma hydrovolcanic tuff breccias. Additionally, large shield volcanoes 10-12 Ma and younger are completely unmarked by erosion, with the exception of one 8.3 Ma volcano that is located on the coast.
     A coarse-grained alkaline gabbro is exposed on the eastern flank of the Marie Byrd Land dome, ~470km east of the center of Neogene uplift. It is the only known intrusive body related to Cenozoic magmatism in Marie Byrd Land, and is therefore likely to represent the inception of Cenozoic magmatism and uplift in this region. The results of recent 40Ar/39Ar dating of the gabbro and associated dike rocks indicate an emplacement time of 34-37 Ma. The uplift and erosion history required to expose this body, at the relatively low elevation of 600-800 m, contrasts significantly with the history of the past 25 m.y., as it is recorded elsewhere in the region. The comparison provides a new perspective on the possibility of mid-Cenozoic plate motion of West Antarctica, with respect to East Antarctica, which may be recorded by displacement of the locus of uplift. Furthermore, the apparent change in erosion rates over the past 35 m.y. appears to reflect the change from pre-glacial to glacial, and from warm-based to cold-based glacial environments. The scenario that seems to best fit the erosional and volcanic history recorded here is one in which glaciation began ~25 Ma, as an ice cap on a low relief landscape near sea level, and gradually expanded as the Marie Byrd Land dome rose and the climate deteriorated. Effective erosion seems to have ceased before 10-12 Ma in inland areas, but persisted in coastal localities until ~6-7 Ma, perhaps reflecting a gradual transition from cold to warm-based glacial conditions. This inference is consistent with recent findings along the western coast of the Ross Sea, ~2000 km west of the Marie Byrd Land dome.

Feb. 18 Susan Avery, Director of CIRES and Professor of Electrical and Computer Engineering, Univ. of Colorado at Boulder, "Water, Science, and the New West."
With many parts of the Interior West experiencing rapid growth rates and already scarce water resources becoming further stressed, many decision-makers and government agencies are seeking new ways to assess the socio-ecological realities of the New West. Identifying and understanding complex linkages between climate, hydrology, ecology, and the changing social structure is key to management of the region's water resources. However, research on water is often fragmented by a disciplinary approach. In response to the research needs, we have put together an interdisciplinary research team to study climate variability and its impacts upon the water cycle in the Interior West. Through a "follow the water" approach from its source in the atmosphere, through the various phases of the natural hydrological cycle, and its coupling to societal uses and ecosystem health, we began a pilot study of the South Platte River basin. The research approach and questions illustrate the complexities and multiple stressors that water decision-makers face when making their decisions. This presentation will illustrate and discuss our results from the South Platte River study and describe our future projects.

Feb. 11 Ulysses Ninnemann, Lamont Doherty Earth Observatory, Columbia Univ, "Drake Passage ocean circulation and climate changes during the Last Deglaciation ."
A variety of ocean model simulations stress the importance of the Drake Passage and the Antarctic Circumpolar Current (ACC) in determining modern ocean structure and water mass distributions globally. Glacial ocean circulation appears to have been dramatically different than in the modern, yet the role of the Southern Ocean in these reorganizations remains uncertain--the paleoceanographic evidence for changes in the ACC is indirect and equivocal. We present new sediment records of ocean temperature (foraminiferal d18O) from the northern edge of the Drake Passage in order to better constrain the nature of deglacial climate and changes in the ACC.

Fall 2001

Oct. 29 Ute Herzfeld, Heisenberg Fellow (German Science Foundation) and INSTAAR, "Mapping and monitoring changes in the Antarctic Ice Sheet from combined RADARSAT SAR and GEOSAT to ERS radar altimeter data analysis."
     Although it is generally understood that the Antarctic Ice Sheet plays a critical role in the changing global system, there is to date still a lack of generally available information on the subject. Much of our knowledge depends on models, but realistic modeling requires observations. Satellite data are an important source of information. One of the challenges today is to develop geophysically meaningful processing software as fast as we can develop new hardware.
     We present maps based on two data types: Synthetic Aperture Radar (SAR) data from the Antarctic Phase of the Canadian RADARSAT, and radar altimeter (RA) data from GEOSAT and ERS-1. Radar altimeter data provide absolute elevation and continent-wide coverage to 81.5S, but have low spatial resolution. In SAR data, elevation is not measured, but the spatial resolution is much better. A solution lies in a combination of both data types. Coreferencing and geolocating of SAR and radar altimeter data is a nontrivial task, because of nonlinear distortion in the SAR data and a general lack of fix points in most areas of Antarctica. Rather than map the entire Antarctic continent in one sheet, data are processed in atlas style. For interpolation of RA data, specific geostatistical methods are applied. Improved kriging methods are developed that utilize local morphologic characteristics, which is particularly important for mapping regions along the Antarctic margin, as these are both topographically complex and play a key role in the study of ice-ocean fluxes and changes in the ice sheet.
     Applications are in monitoring changes in Antarctic glaciers, ice streams and ice shelves, and in detailed regional studies of outlet glaciers of the inland ice that are particularly exciting. At this time, the Antarctic atlas contains a total of 136 maps, some of which will be presented, including a new RADARSAT/ERS map of the Lambert Glacier/Amery Ice Shelf System and part of its drainage area, and detailed maps of numerous glaciers.

Oct. 08 Jim Maslanik, Aerospace Engineering and PAOS"Development and applications of a small unpiloted aerial vehicle for polar research."
The University of Colorado is presently involved in research to develop and test the use of a class of small unpiloted aerial vehicle (UAVs) for meteorological and cryospheric science applications. This talk will summarize experience to date with the "Aerosonde" UAV - a small, relatively low-cost aircraft capable of carrying a variety of lightweight instruments. Characteristics of the Aerosonde will be described, and results from flight operations in the Barrow, Alaska area will be presented. These include applications for sea ice mapping, atmospheric sounding, and monitoring of shoreline conditions. Potential of the Aerosonde for other research tasks such as wildlife studies, environmental impact monitoring, and ice sheet remote sensing will be introduced.

Sept. 17 Lisa Morgan, US Geological Survey, "New discoveries in Yellowstone Lake: Results from high-resolution sonar imaging, seismic reflection, and submersible surveys."
     Recently completed high-resolution surveys in Yellowstone Lake show an irregular lake bottom covered with dozens of features directly related to hydrothermal, tectonic, and volcanic processes. Over 150 new hydrothermal vent sites, several very large (>500 meter diameter) and many small hydrothermal explosion craters, elongate fissures cutting post-glacial (<12 ka) sediments, siliceous hydrothermal spires 5-8 m tall composed primarily of silicified bacteria and diatoms, deformed lacustrine sediments associated with domal structures and hydrothermal vents, submerged former shorelines, and a recently active graben have been identified.
     Discoveries from the 1999-2000 surveys are a direct result of a systematic field approach combining high-resolution bathymetric mapping and seismic reflection sub-bottom profiling with remotely operated vehicle submersible follow-up observations and sampling. The West Thumb basin survey identified rhyolitic lava flows, now covered with glacial and lacustrine sediments, infilling the 140-ka West Thumb caldera. This led to the realization that much of the northern part of the lake may also be underlain by rhyolitic lava flows. These inferred flows do not have mapped subaerial equivalents and may represent a new undiscovered major volcanic feature that exerts controls on the geomorphology of the lake, localization of hydrothermal systems, and major explosion events. Our studies in the northern lake show that the glaciolacustrine deposit of Stevenson Island, rather than being underlain by thick glacial debris, may rest upon a large previously unidentified, rhyolitic lava flow. In addition, sub-bottom seismic profiling has allowed widespread identification of post-glacial sediments that are deformed, disturbed, and altered due to hydrothermal vent channelways and subsurface migration of hydrothermal fluids. Chemical studies of the vents indicate 20 percent of the total deep thermal water flux in Yellowstone National Park occurs on the lake bottom and contain potentially toxic elements that significantly affect lake chemistry and possibly the lake ecosystem. The surveys cover about 40 percent of the lake floor, within the 630-ka Yellowstone caldera. Formation of hydrothermal features is related to deep-seated fluid circulation above a now cooling magma chamber. Hydrothermal explosions result from the transformation of water to steam, perhaps due to changes in confining pressure that result from (and accelerate) failure and fragmentation of overlying cap rock. Objectives of this work include understanding the geologic processes that shape the lake and how they affect the present-day lake ecosystem.
     Future surveys of Yellowstone Lake will contrast the geologic framework of the lake and hydrothermal processes within, along, and outside the caldera boundary. Corresponding author: U.S. Geological Survey, Box 25046, MS 966, Federal Center, Denver, CO 80225, lmorgan@usgs.gov

Sept. 10 Mark Losleben, INSTAAR. "Mountain snowpack and variability in three western United States mountain ranges."
Mark Losleben, Nick Pepin, Mike Hartman. Reliable water supplies are crucial to virtually every aspect of life, and snowpack is a prime water source in much of the western United States. With an eye toward future snowpack conditions, especially variability, results are presented for three major mountain range areas: the Colorado Rockies, California Sierra Nevada, and the Oregon Cascades. Winter precipitation patterns in the adjacent lowlands are also compared to mountain snowpack patterns. Snowpack variability, both overall totals and east:west slope differences, are greatest in the Cascades, and least in the Rockies. Snowpacks are decreasing in the Cascades on both slopes, and on the east slope of the Rockies, compared to no trend in the Sierra Nevada and the west slope of the Rockies. In contrast, equivalent winter precipitation on the adjacent lowlands is increasing everywhere except west of the Cascades. Atmospheric circulation does appear to be significantly affected by ENSO phase in any of the three areas, however snowpack is affected in the Oregon Cascades. The issue of snowpack variability may be linked to available moisture sources. Unlike the Sierra Nevada or the Cascades, the Colorado Rockies may receive snow from the Gulf of Mexico in addition to the Pacific Ocean, thus greatly lowering its inter-annual variability. Suggestions of future conditions include an overall decrease in western US snowpack levels, and particularly on the east slope of the Cascades. Little significant change will occur in the Sierra Nevada, and the west slope of the Colorado Rockies, but the east slope snowpack could increase.

Apr. 09 John Hoffecker, INSTAAR, "East European Environments and the Ecology of the Neanderthals."
Isolated from the moderating influence of the North Atlantic, climates in Eastern Europe are significantly cooler and drier than those of Western Europe. The Neanderthals, who evolved in Western Europe during the cooler phases of the late Middle Pleistocene, were the first hominids to settle widely across Eastern Europe. However, they appear to have abandoned much of the East European Plain during the coldest phases of the Late Pleistocene. Although morphologically adapted to cold climates and consuming a diet high in meat, the Neanderthals seem to have lacked both the foraging range and complex technology of modern humans in very cold environments.

Apr. 02 Russ Graham, Denver Museum of Nature and Science, "Triggers, Thresholds, Russian Roulette, and Pleistocene Extinctions"
The primary concerns for endangered species today are habitat loss and geographic range reduction. These are the same concerns that the Pleistocene megafauna faced about 11ka radiocarbon. However, in the Pleistocene, habitat loss and reductions in geographic range were driven by climate and environmental change; whereas, today humans are one of the primary driving forces. Continuous climate change throughout the Pleistocene selected for the evolution of new habitat mosaics and the "extinction" of old ones (e.g.., parklands, savannas, etc.). In addition, these environmental changes reduced the ranges of both large and small mammals but because the probability of extinction is a function of geographic range and body size, large mammals were preferentially selected for extinction. With this model, climate change at the end of the Pleistocene need not be unique but it probably served as a trigger for a threshold effect. Once populations dropped below critical levels, the megafauna was doomed, irrespective of human involvement!

Mar. 19 Helmut Elsenbeer, University of Cincinnati, "Soils and Land-Use History in the Southern Alps."
The present, prevailing impression of untouched nature, if not wilderness, in many southern Alpine valleys is deceptive: the thick and extensive forest cover is but a fairly recent consequence of a shift in socio-economic conditions that rendered subsistence agriculture and intensive use of forest resources obsolete. A case study in the Val Onsernone of southern Switzerland had the objective to determine the responsiveness of soils to rapid land-use and land-cover change. A chronosequence of forest regrowth, simulated by space-for-time substitution, encompassed grassland as the presumed initial stage of land-use change and several stages of forest (Fagus sylvatica) regrowth up to a median stand age of one-hundred years. This approach attributes any changes in soil properties to the effect of increasing forest cover, as other •soil formingê factors, such as lithology, climate, and topography, were held constant by judicious site selection. Both soil physical and soil chemical properties responded with an inferred lag time of about 50 years. The morphologically and chemically most striking responses are those indicative of more intense podsolization as a consequence of increasing stand age: the disappearance of the A horizon and the appearance of an incipient E horizon, the pronounced increase of amorphous silicon with depth, the decreasing crystallinity of •freeê aluminum, and the massive increase in anion exchange capacity. These changes are, in turn, reflected in secondary features such as partitioning of soil phosphorus into different fractions. These results are summarized in the hypothesis of a •podsol pendulumê whose departure from a presumed equilibrium state is controlled by land-use and land cover change, in this case itself a function of socio-economic factors.

Feb. 19 Mark Dyurgerov, INSTAAR, "The contribution of mountain and subpolar glaciers to sea level rise appears to be increasing; can we predict this for the 21st century?"
Mountain and subpolar glaciers have been accelerating their rate of ice wastage and sensitivity to climate change in recent years. During the 1961-98 period, these glaciers lost about 7 m of ice, or about 5000 km3 of water, most of which ran off to the ocean and increased sea-level by about 13 mm (about 20% of total sea level rise). These extreme changes of glacier regime may have been the largest of the last hundred years. The increasing rate of glacier wastage in Central Asia, Canadian Arctic, and Alaska occurred at the same time as mass gain and frontal advances in Scandinavia and New Zealand and steady-state conditions in Caucasus and Altai. The lack of synchrony and an increase in spatial variability of all parameters seems to be a distinguishing feature of new modes of climate change. These modes are not yet satisfactorily explained. One of the main uncertainties in determining the influence of glaciers on sea level change is the unknown regime of individual ice caps around Antarctic and Greenland ice sheets, Patagonian Ice Fields, and the largest glaciers in Alaska. The small, cold glaciers around the margins of Antarctica may play a larger role in the future with global warming. Although the area of ice in temperate regions of Earth will surely decrease, the area of glaciers around Antarctica contributing to sea-level rise may increase.

Selected Abstracts INSTAAR Noon Seminars

Selected Abstracts
INSTAAR Noon Seminars