INSTAAR Noon Seminar-Abstracts

Spring 2008

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.

Our tephra based age model for Haukadalsvatn sediments indicates that sedimentation rates in the early Holocene were less than half the late Holocene sedimentation rates with a substantial increase around 5 ka and highest around the Little Ice Age (0.8 to 0.1 ka). Given the BSiO2 is a direct measure of the primary production within the lake and thus a factor of summer water temperatures and nutrition, it records highest summer temperatures of the whole record between 9 and 7 ka. This is also the time when TOC% is rising and in-phase with the BSiO2. Clear trend towards deterioration is detected in the record from 6 ka indicating the beginning of the Neoglaciation. During the last 8 ka a couple of large but abrupt departures of the two proxies reflect significant perturbations to the entire lake catchment and or within lake processes, most likely explained by soil erosion and introduction of aged carbon into the lake system. Interestingly these perturbations seem to coincide with well-known, major, volcanic eruptions in Iceland. The fact that the first long term decoupling of BSiO2 and TOC% occurs several centuries before settlement suggests that the Haukadalsvatn system is recording non-human climate impacts. The carbon record is relatively stable throughout the period of settlement (870-930 AD) but intensifies abruptly at around 1250 coinciding with the onset of the Little Ice Age. Several peaks in the TOC% content characterize the Little Ice Age reflecting high soil erosion conditions. These show periodicities that might be attributed to intervals of positive North Atlantic oscillation (NAO) mode with colder than normal temperatures around Iceland and strong Atlantic westerlies and northeast trade winds.

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."

Will our kids, and their kids, have enough snow to ski in the future?

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.

10 Mar. Detlev Helmig, INSTAAR.
"INSTAAR goes to sea."

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.

Fall 2007

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.

Spring 2007

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.

3 Apr. Richard Reynolds , USGS.
"Dust emission in North America."

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.

05 Mar. E. James Dixon, INSTAAR.
"Alaska’s Oldest Man."

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.

Fall 2006

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.

Spring 2006

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).

Literature cited:

Blecker, S.W., 2005. Silica Biogeochemistry across a grassland climosequence, [Ph.D. Dissertation], Colorado State University, Fort Collins, 142 p.
Blecker, S.W., McCulley, R.L., Chadwick, O.A. and Kelly, E.F. (In Review).
Silica biogeochemistry across a grassland bioclimosequence. Global Biogeochemical Cycles.
Conley, D.J., 2002, Terrestrial ecosystems and the global biogeochemical silica cycle, Global Biogeochemical Cycles, 16, p. 1121-1128.
Kelly, E.F., Chadwick O.A., and Hilinski T.E., 1998, The effect of plants on mineral weathering, Biogeochemistry, 42, p. 21-53.
Kelly, E.F., McCulley R.L., Blecker, S.W., Chadwick, O.A., Ziegler, K., Derry, L.A. and Burke, I.C., 2002, The Biogeochemistry of Silica in Grasslands Ecosystems of the central Great Plains of North America, American Society of Agrononmy Abstracts.
Kidder, D. L., and E. H. Gierlowski-Kordesch (2005), Impact of grassland radiation on nonmarine silica cycle and Micoene diatomite, Palaios, 20, 198-206.

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

Selected Abstracts INSTAAR Noon Seminars

Selected Abstracts
INSTAAR Noon Seminars