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Selected Abstracts
INSTAAR Grad Student Talks

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• INSTAAR Grad Student Talks

Fall 2009

Nov. 19     Jordan Parman, INSTAAR.
"Elevational controls on organic and inorganic nutrients in stream waters, Boulder Creek Watershed, Colorado Front Range."

High-elevation ecosystems have become the focus of recent biogeochemical research due to their unique and complex processes, but also because these systems may serve as an early warning system for the potential effects of climate change. In the Colorado Front Range, it is expected that alpine areas will continue to experience greater annual precipitation, as well as an increase in atmospheric deposition of inorganic nitrogen. Past studies have shown that these mountain systems tend to amplify such environmental changes in specific areas of the landscape. The Landscape Continuum Model (LCM) proposed a conceptual framework for how mountain ecosystems accumulate and redistribute exogenous material from the atmosphere and endogenous material derived from the mountain itself, emphasizing the importance of transport processes and redeposition of nutrients and water across highly varying and complex terrain. This study tests the LCM by comparing and contrasting changes in organic and inorganic nutrients in stream waters of headwater catchments along an elevational gradient in the Colorado Front Range. Water samples were simultaneously collected at four gauged headwater catchments: (1) Green Lakes Valley (3,500 m); (2) Como Creek (2,900 m); (3) Gordon Gulch (2,400 m); and (4) Betasso (1,830 m). All water samples were measured for DOC, DON, DOP, nitrate and ammonium. Additionally, spectroscopic techniques were used to determine the source and quality of DOC. These measurements, along with supporting information on soil C:N ratios and climate data, allow us to determine how elevational position controls: (a) the redistribution of exogenous materials from the regional environment such as nitrate in wetfall; and (b) endogenous sources originating from montane areas such as DOC and DON, while controlling for catchment size, aspect, and underlying geology.

Nov. 12     Barbara-Lynn Concienne, EBIO.
"Microbial communities in newly deglaciated soils of the Middle Fork Toklat Glacier
Denali National Park and Preserve, Alaska."

The forefront of the Middle Fork Toklat Glacier sits at about 1300 meters on the northern slope of the Alaska Range which is about 60oN. It also sits in the rain shadow of Mt. McKinley and surrounding peaks creating conditions similar to the high peaks of Argentina, Peru, Colorado, and the Himalayas. In addition, Denali National Park and Preserve sits on the cusp of the Boreal Forest ecosystem to the south and the Northern Slope Tundra ecosystem to the north and is believed to be highly susceptible the effects of climate change. The Middle Fork Toklat Glacier is what you would call a dirty glacier; beginning about 1 km from the elevation line of accumulation, the lateral and medial moraines become seasonally exposed from snow pack. Like most glaciers around the world, the Middle Fork Toklat is retreating at several meters per year. But unlike most other glaciers, what we find is an exposed rocky moraine left behind about 100 years ago from the last glacial advance in Alaska that begins on the ice of the glacier and extends three kilometers down the valley. Here we investigate microbial activity over two seasons. Early analyses indicate microbial activity is occurring in the substrate on the glacier, there is a shift in microbial community along the chronosequence, there is a similarity between communities here and around the world, and there is a correlation between mineralogy and microbial activity.

Oct. 29     Lee Stanish, INSTAAR.
"Spatial variation in benthic diatom community composition in Antarctic stream ecosystems."

Stream microbial mats are dynamic communities of photosynthetic and heterotrophic organisms. Diatom communities in microbial mats are influenced by successional processes and scouring events that together act to shape stream benthic habitats. In ephemeral streams of the McMurdo Dry Valleys (MDV, Antarctica), previous work has demonstrated that in streams within the MDV, the diatom composition in is determined largely by the annual and historical flow regime. This study found that the relative abundances of endemic diatom species increases under a colder, lower stream flow regime. Conversely, warmer, higher-flow conditions favor widespread diatom species, and concomitant decreases in diatom species diversity occur at either extreme. However, we still do not understand the spatial variation of diatom communities within a stream reach or how much communities vary from stream to stream. This is important because diatoms are often used as ecological indicators and we don’t yet understand enough about spatial variability of Antarctic diatom species to correlate diatom community changes to environmental changes, despite previous efforts. This study aims to define these spatial variations in microbial mats within and across two Dry Valley streams. Environmental factors, particularly stream flow, are currently being modeled in order to identify drivers of community composition. Results show that there are significant differences between diatom communities within and across streams, indicating the importance of considering spatial scale in diatom monitoring projects even in “harsh” environments.

Oct. 22     Lu Alves, INSTAAR.
"Variation in live aboveground biomass along an elevational gradient of a tropical moist forest (Brazil)."

The Brazilian Atlantic forest, a global center of vascular plant diversity and endemism and one of the most threatened tropical forests in the world, sill covers around 14 million hectares, or 16,5% of the total extra-Amazonian tropical forests in South America. Despite its extension, forest carbon pools and fluxes of the Atlantic forest have seldom been studied, and standardized estimates of aboveground stocks of live and dead biomass are rarely available. Here I synthesize our recent results from a network of permanent plots established in 2006-2007 to evaluate forest structure and live aboveground biomass (AGB) variation along an elevational gradient (0-1,100m asl) of coastal Atlantic Forest in SE Brazil.
The Atlantic forest still retains a significant aboveground biomass stock (228 ± 28 Mg ha-1; 144-323 Mg ha-1) in comparison to other Neotropical forests. Total live biomass increased with elevation, with large and very large trees accounting for 68% of the total AGB accumulated at submontane and montane forests. A remarkable simple two-factor model explained 92% of the variance in total stand-level AGB along the elevational gradient. In the next years, long-term monitoring of those permanent forest plots will be crucial to quantify changes in carbon stocks and to evaluate.

Oct. 15     Jennifer Petrzelka, INSTAAR.
"Three-dimensional quantification of meltwater flow through a snowpack using a snow guillotine: Methods, fieldwork, and some preliminary results."

In areas containing seasonal snowpacks, snowmelt contributes significantly to the hydrological cycle. Thus, quantifying the spatial distribution of flow through a snowpack is essential to accurate hydrograph interpretation and representation in snowmelt runoff modeling. Movement of liquid water through snowpacks is generally recognized to occur in distinct flow paths rather than as uniform flow through a homogeneous porous medium. Although dye tracer experiments have provided valuable qualitative information on meltwater flowpaths, quantitative descriptions of their spacing and location are not commonly available because of the difficulty in precisely excavating and measuring pathways. This makes it difficult to study scale and time-dependent processes such as the evolution of preferential flowpaths. Here we provide proof-of-concept using a new instrument we term ‘snow guillotine’ that provides quantitative information from dye tracer experiments in melting snowpacks. The structure of the snow guillotine allows the ability to take cross-sectional slices at 1-cm intervals of a snowpit where dye tracer has been applied. Photographs are taken of each cross-section over a one meter distance. Application of image processing and geostatistical analysis allows collection of high resolution (1cm3), three-dimensional data on meltwater flow through a snowpack.

Results from 2003 illustrate preferential flowpaths, with the majority of vertical flow occurring in the upper 20-55cm of the snowpack, while fewer preferential flowpaths are apparent below 100cm. The number of vertical flowpaths in the upper half of the snowpack averaged almost 100 per m2, with the highest number of flowpaths reaching almost 300 per m2. Layer interfaces were found to significantly increase the volume of dye, indicating dominance by lateral flow at these boundaries. Geostatistical analyses showed that there were large increases in correlation lengths and the connectivity function at stratigraphic layers in contrast to low values between layers. Preliminary results for guillotine experiments carried out for the 2009 melt season indicate the evolution of preferential flow did not transition from distinct flowpaths to matric flow as obviously as in 2003. This difference may be partly attributed to the difference in weather patterns between the two seasons, with colder temperatures and frequent precipitation events dominating the 2009 melt season.

Oct. 08     Mariah Walton, INSTAAR.
"West Greenland Cruise JR175: Reconstructing the Quaternary retreat of the Greenland Ice Sheet."

August and September of this summer saw me aboard the British Antarctic Survey’s RRS James Clark Ross off the West Coast of Greenland. The objective of this JR175 scientific cruise was to obtain geological and geophysical data to characterize the past behavior, extent, and retreat of the Jakobshavns Isbrae—the largest ice stream on Greenland’s West coast. The primary areas of study were Disko Bay and the Vaigat, into which Jakobshavn directly drains, the continental shelf and slope, and the neighboring Umanak fjord system. Swath bathymetry and seismic profile data were collected in tandem with ocean sediment cores (vibro, box, and gravity cores) to provide a comprehensive physical and paleoceanographic data set. Foraminiferal assemblages will be counted at INSTAAR using samples taken from 28 of the 55 cores taken to constrain the retreat and possible re-advance of ice in the Disko and Umanak systems and to correlate changes in ice with changes in Atlantic and Arctic currents. This talk will summarize how bathymetry and seismics relate to core site selection and the cores themselves, how cores are collected and processed, and how forams will be used as paleoceanographic indicators, as well as providing insight into the role of a lowly grad student at sea.

Oct. 01     Ben Schupack, INSTAAR.
"Pushing the limits of volcanic cryptotephra detection in the Arctic."

During explosive volcanic eruptions, pyroclastic material (tephra) ejected into the atmosphere is largely deposited proximal to the volcanic source. However, if eruptions are explosive enough to penetrate the stratosphere, fine tephra particles may be transported many thousands of kilometers, sometimes globally, depositing on distal lands, oceans, and ice caps. Elusive grains invisible to the naked eye (< 100 µm) termed cryptotephra can serve as key chronostratigraphic markers well beyond the range of visible tephra beds, constraining sediment ages and enhancing regional correlation.

In this pilot study, we push the limits of cryptotephra detection in distal High Arctic clastic Holocene lake sediments. Clastic sediments pose a significant problem for isolating and concentrating cryptotephra grains just tens of microns in size. Using a sequence of acid digestions, sieves, and heavy liquid separations of varying densities we successfully reduced the amount of clastic matrix material and increased the probability of finding cryptotephra. By carefully searching through thousands of minerogenic grains for glass shards using scanning electron imagery and energy-dispersive x-ray analysis (EDS), our study revealed cryptotephra in a lake basin in Spitsbergen, Svalbard, located more than 1000 km from the nearest source of Holocene tephra. The two glass shards discovered in a single sample have been analyzed by electron microprobe together with Icelandic reference samples, but the source eruption is as yet unidentified. By re-polishing and re-analyzing the particles, we increased the amount of quantitative compositional data that could be acquired from such sparse, fine glass shards. The striking morphological similarity between phytoliths (biogenic silica) and cryptotephra also adds to the challenge, but these are rapidly distinguished by EDS analysis.

Sept. 17     Kurt Refsnider, INSTAAR.
"Long-term records of ice sheet dynamics and erosion on Baffin Island."

The Baffin Island landscape holds records of Laurentide Ice Sheet erosion and dynamics spanning the last 2+ Ma, allowing us to investigate processes at a variety of time scales. Glacial and proximal glaciomarine sediments deposited on coastal forelands are being used to test the regolith hypothesis for the Mid-Pleistocene Transition. This transition in the duration of glacial cycles from 40 ka to 100 ka is one of the most profound changes in Plio-Pleistocene changes, yet its cause remains enigmatic. On the interior of the island, we are studying spatial patterns of glacial erosion and subglacial water transport during more recent glacial cycle, which will in turn provide further insight into from where on the landscape the coastal glacial deposits were derived. Apparently polar bears have also become interested in some of these questions, recruiting an increasingly large number of individuals to climb around on the coastal cliffs, dig into recent glacial deposits, and chase away any Southerners caught collecting samples from the area.

Sep. 10 Tyler Jones, INSTAAR.
"Siple Dome ice cores: Implications for West Antarctic climate and ENSO events."

Siple Dome, West Antarctic ice cores receive the majority of their precipitation from a Pacific Ocean moisture source. Pacific climate patterns, particularly the El Niño-Southern Oscillation, affect the local temperature, atmospheric circulation, and snow accumulation at Siple Dome. Isotopic signals (∂D, ∂18O, and deuterium excess), from seven spatial shallow ice cores reveal an intense micro-climate around Siple Dome heavily influenced by South Pacific climate and the location of the Amundsen Sea Low Pressure Area. At a time when El Nino events have been increasing since the mid-Holocene, Siple Dome itself detects both El Nino and La Nina, but has a bias toward La Nina conditions- a phenomenon contrasted in four deep Antarctic ice cores. Near term increase in ENSO frequency is detected from spectral analysis of a high-resolution Siple Dome ice core dating back 350 years.

Spring 2009

Apr. 30     Phil Taylor, INSTAAR.
"Global coherence of organic carbon-nitrate relationships from soils to the sea."

The global carbon and nitrogen cycles are incredibly complex and undergoing rapid change, which makes it difficult yet exciting to pin down controls on the sources, transformations and sinks of these elements. Scientists from various disciplines have made significant headway in characterizing these cycles, but often with little integration of ideas or findings across earth’s ecosystems. Yet, biogeochemists working in soil and aquatic systems have found an intriguing and strong inverse pattern between dissolved organic carbon and nitrate, which are two biologically reactive constituents central to modern global carbon and nitrogen cycling. Our curiosity concerning the global strength of this trend, particularly in its implications for managing nitrogen in the environment, led us to inspect organic carbon-nitrate relationships in all of earth’s ecosystems. We found a robust correlation, and use principles of ecological stoichiometry to explain the patterns. We believe pervasive resource-consumer imbalance, when DOC:NO3 ratios match the stoichiometric C:N ratio of microbial demand (or not), mediates heterotrophic nitrogen assimilation, denitrification and nitrification, which collectively generate these universal trends.

Apr. 23     Sean Bryan, INSTAAR.
"Changes in deep ocean circulation and carbon cycling during the Last Deglaciation: Evidence from the Arabian Sea"

The timing of changes during the most recent deglaciation reveals a tight association between deep ocean circulation, ocean carbon cycling and climate. During the deglaciation, atmospheric pCO_2 rose and atmospheric radiocarbon activity (?^14 C) declined in two steps; the first during Heinrich Event 1 (H1) and the second during the Younger Dryas (YD). These changes coincided with warming in Antarctica, cooling in Greenland and reduced North Atlantic Deep Water (NADW) formation. Between these two steps, during the Bølling/Allerød or Antarctic Cold Reversal, atmospheric pCO_2 and ?^14 C leveled, Greenland warmed abruptly, Antarctica cooled slightly, and NADW formation increased. The concurrent changes in atmospheric pCO_2 and ?^14 C imply that the CO_2 added to the atmosphere must have been depleted in radiocarbon. Support for this idea was found in the reconstruction of ?^14 C in intermediate waters off the coast of Baja California [Marchitto et al., 2007 /Science/], which revealed pulses of radiocarbon-depleted DIC during H1 and the YD, at the same time as atmospheric pCO_2 rose and atmospheric ?^14 C declined. This radiocarbon-depleted carbon could only have been sourced from a sluggishly-ventilated deep ocean water mass, suggesting that changes in deep ocean circulation likely played a prominent role in the deglacial pCO_2 rise.

In this talk I will discuss new intermediate water radiocarbon activity reconstructions from the Arabian Sea. These reconstructions come from two sediment cores: RC27-14 (596 m water depth) and RC27-23 (820 m water depth). Taking advantage of the strong similarity between the ?^15 N of organic matter in these cores [Altabet et al., 2002 /Nature/] and the ?^18 O of the GISP2 ice core [Grootes and Stuiver, 1997 /J. Geophys. Res./] we created calendar age models independent of C-14. Intermediate water ?^14 C were then calculated using calendar ages along with C-14 ages of benthic foraminifera. Initial results indicate the presence of C-14 depleted DIC in the Arabian Sea during the time of Heinrich Event 1. Intermediate water ?^14 C from the shallower of the two Arabian Sea cores is less depleted than at Baja California; however, ?^14 C at the deeper site appears to show even greater depletion. The presence of radiocarbon-depleted DIC in the Arabian Sea indicates that the ?^14 C signal is not isolated to the northeast Pacific, and would be consistent with a signal sourced in the Southern Ocean and transmitted through Antarctic Intermediate Water.

Apr. 16     Dan McGrath, INSTAAR.
"Sediment plumes in Sondre Stromfjord, Greenland as a proxy for runoff from the Greenland Ice Sheet."

Recent warming has been particularly acute in the Arctic, leading to a strongly negative mass balance of the Greenland Ice Sheet (GrIS). Meltwater runoff is an important component of an ice sheet’s surface mass balance, although in situ measurements to quantify run-off are hindered by logistical difficulties associated with the large, remote and spatially diverse nature of the ice sheet. Modeling studies suggest that run-off accounts for approximately 30-50% of the annual mass loss from the ice sheet, however, there is a need to more accurately quantify run-off with empirical measurements. The purpose of this research is to determine if remote sensing can be used to characterize the onset, duration and intensity of meltwater runoff. The primary field site includes a 6,280 km2 basin of the ice sheet, which runs off into the Watson River before flowing into Sondre Stromfjord, the longest fjord in west Greenland. The onset and duration of runoff into Sondre Stromfjord was compiled using the MODerate-resolution Imaging Spectroradiometer (MODIS) Band 1 (620-670 nm, 250 m resolution) from 2001-2008. Over the 8 yr study period, plume formation occurred 10 days earlier. The onset of ablation at the S5 (490 m asl, 6 km from ice margin) Kangerlussuaq Transect automatic weather station and plume formation are positively correlated (r2=0.88, 2003-2008). Likewise, there is a positive correlation (r2=0.93) between the cessation of ablation and the waning of the plume. Sediment plume length variability throughout the 2007 and 2008 melt seasons is strongly correlated (r2=0.83) with a 4-day average Watson River discharge. This relationship is applied to plume length variability derived from MODIS imagery to reconstruct cumulative Watson River discharge. Reconstructed values using plume length are within 10% of measured discharge values.

Apr. 09     John Knowles, INSTAAR.
"Carbon cycling above treeline: eddy covariance results from high-elevation (3480 m a.s.l.) alpine tundra at Niwot Ridge, Colorado."

Ecosystems in topographically complex (mountainous) terrain are responsible for a majority of land-atmosphere CO2 exchange (NEE) across the western United States due to high inputs of winter precipitation as snowfall. NEE in these regions has been historically difficult to quantify using the eddy covariance (EC) method, however, due to complexities in surface terrain that lead to irregularities in streamline air flow, particularly advective fluxes during periods of low turbulent mixing. This research evaluated the applicability of EC to an alpine tundra site at the Niwot Ridge Long Term Ecological Research Project (LTER), and subsequently investigated meteorological factors controlling observed NEE. Persistent high winds, a relatively short turbulent flux footprint, and the nearly flat ridge-top location of the study site promoted 85% mean annual energy balance closure and general fulfillment of basic EC methodological requirements. In all, the alpine tundra was a net source of 6.81 g C m-2 to the atmosphere during 2008, notwithstanding a total of 2.21 g C m-2 was sequestered during the 87-day growing season, defined as the period between the day when the slope of the 0.5-hour mean cumulative CO2 flux changed sign from positive to negative (June 16) and vice versa (September 10). Peak rates of summertime CO2 uptake and wintertime CO2 respiration were determined to be of comparable magnitude, fluctuating between 0.1 – 0.2 mg CO2 m-2 s-1 (negative during summer). Rates of CO2 sequestration during the growing season increased most acutely with soil temperature, corroborating documented preeminence of this relationship at other alpine locations. Net CO2 sequestration was 22% less during the longer (94-day), warmer 2007 growing season, highlighting a possible inverse relationship between alpine growing season length and net CO2 sequestration on Niwot Ridge. Drought stress resulting from decreased wintertime precipitation is initially hypothesized as a mechanism for this trend.

Mar. 12     Caroline Alden, INSTAAR.
"If only we had a Flux Capacitor: Using the stable carbon isotope to track fluxes, sources, and sinks of atmospheric CO2."

As atmospheric greenhouse gas concentrations rise, researchers seek to identify how Earth’s climate and carbon cycle are affected. In order to close the atmospheric CO2 budget, several major factors must be accounted for: fossil fuel flux, ocean flux, and land flux. The rare stable isotope of carbon, 13C, can be used as a tool to help distinguish between these fluxes. One drawback to this method is that photosynthesis and respiration are not contemporaneous, and because the 13C of atmospheric CO2 is being continuously depleted through the burning of 12C-rich fossil fuels, there is an isotopic “disequilibrium flux” between CO2 moving into and out of the ocean and land reservoirs. In this study, we use a combination of atmospheric CO2 and 13CO2 data, fossil fuel emission estimates, and recent ocean model results for the ocean CO2 flux, within a box-inverse model. We calculate time series of land flux, disequilibrium flux and photosynthetic fractionation from 1990 through 2006. Our findings reveal that if ocean variability is as small as is suggested by the ocean model, and the isotopic variability is forced into the disequilibrium flux, then the resulting disequilibrium flux has very large interannual variability (~40 PgC‰/yr), and an increasing trend. An intriguing possibility is that both the ocean model predictions and the atmospheric measurements can be satisfied by driving the variability into the photosynthetic fractionation term, εab. Under this scenario, relatively small interannual variations in net carbon exchange of C3 and C4 vegetation would be sufficient to explain the otherwise seemingly incongruent nature of the ocean model results and atmospheric observations. Disequilibrium flux and other terms will be explained, and the use of 13C as a tool to track carbon will be discussed. Best estimates of land, ocean, and disequilibrium fluxes, as well as photosynthetic fractionation and C4 net terrestrial exchange will be presented.

Mar. 05     Tyler Jones, INSTAAR.
"Hook echoes, radio velocity fields, and the science behind tornados: Storm chasing in Tornado Alley"

Each year, a group of scientists, filmmakers, and adventurers hunt down tornadoes to gain invaluable scientific data, which is used to better predict storms and ultimately save lives. Discovery Channel's Storm Chasers is based on the scientists who chase tornados for a living. For three months a year these chasers drive 1000's of miles across tornado alley in the American Mid-west in search of violent storms. Their caravan of vehicles include the TIV (Tornado Intercept Vehicle), DOW (Doppler On Wheels), PROBE (new mobile survey vehicle), SCOUT (mobile survey) and TVN (TornadoVideos.net vehicle). Various high-powered radar was used to detect tornado like signatures while storm chasing. Tornadoes are often located at the center of a hook-shaped echo on the southwest side of thunderstorms. The hook is best observed in the reflectivity field. Pre-chase information was referenced using NOAA's Storm Prediction Center including Mesoscale discussions, convective outlooks, and severe! weather watches.

Feb. 26     Brian Seok, INSTAAR.
"Developing a process-based atmosphere-snow gas exchange model."

Many once believed that snow provided little or no influence on atmospheric chemistry and composition. In contrast to that belief, atmosphere-snow gas exchange research suggests that snow does play a significant role in controlling atmospheric chemistry and composition. With unprecedented changes in snow cover from climate change, I am interested in knowing how these changes will affect the atmospheric chemistry and composition, and how these processes will feedback to the change in climate.

To investigate this, I need to rely on models, because in situ observations of physical and chemical snow properties, and many other important variables for understanding the interaction that occurs at the atmosphere-snow interface are generally scarce and difficult to collect at the global scale, but current atmosphere-snow gas exchange models poorly simulate the process in which trace gases are released from, deposited into, and transported through the snowpack. This is due to insufficient understanding and parameterization of the chemical and physical snow properties, snow depth, and biogeochemical properties of the under snow substrate for integration into these models. I believe I have collected sufficient data over the past 2 years that will supplement currently available data from other studies and allow me to build a process-based atmosphere-snow gas exchange model. Therefore, I propose to develop such model to help quantify what variables are important and drive the atmosphere-snow gas exchange.

Feb. 19     Xavier Faïn, Desert Research Institute, Reno.
"The role of snow surfaces in the global mercury cycle: Implications for polar and temperate areas"

Mercury (Hg), a persistent and toxic heavy metal, is present in the environment in various chemical forms. In the atmosphere, gaseous elemental mercury (Hg0, GEM) is the predominant form of mercury (>95%) and can be converted to divalent Hg species (Hg(II)) by oxidation processes. Divalent Hg species (Hg2+) are subject to rapid wet and dry deposition in terrestrial ecosystems. Some of the Hg2+ deposited in aquatic systems and sediments is transformed into organic methylmercure. Although inorganic Hg species have severe health effects on humans, methylmercury is thought to be the highly toxic species involved in bioaccumulation in aquatic food chains. In thousands of lakes in North America, Europe, and Asia, methylmercury contamination of fish negatively impacts the health of humans and wildlife, particularly affecting populations whose traditional diet is based on seafood (e.g. in the Arctic).

The global biogeochemical cycle of mercury is complex and involves interactions between all natural reservoirs. Among them, the exchanges between atmosphere and cryosphere, although poorly quantified, may play an essential role. Snow surfaces cover up to 50% of land masses in the Northern Hemisphere in winter, and snowpacks probably constitute a temporary reservoir of mercury. Investigation of GEM dynamics in the snow interstitial air of various temperate and polar locations showed that snowpacks could act as a sink or as a source of GEM. Notably, at Summit, Central Greenland, we observed reactive mercury chemistry in the first three metres of the snowpack, which translated to daily and seasonal variations in Hg° concentrations in the interstitial air of the snow. Similar measurements are presently initiated at the site of Niwot Ridge (CO) as part of a new collaboration between INSTAAR and DRI. Recent atmospheric monitoring at Storm Peak Laboratory (Steamboat Spring, CO) suggests high deposition of Hg onto the snowpack. The fate of Hg during snowmelt and the possible contamination of ecosystems may be major issues in high population density.

Feb. 12     Teresa Legg, INSTAAR.
"The role of microbial communities in groundwater arsenic dissolution: A case study from Araihazar, Bangladesh"

Arsenic contamination of drinking water sources is a global human health concern, especially in the Ganges-Brahmaputra Delta (GBD) region of Bangladesh where natural groundwater arsenic concentrations are 10 times the World Health Organization's limit. There is evidence that microorganisms facilitate arsenic dissolution through cascading reduction and oxidation (redox) reactions involving labile organic substrates in groundwater, and humic substances, iron (Fe) and arsenic (As) in the aquifer sediments. Pure culture studies of organisms isolated from arsenic-rich environments have shown that a phylogenetically diverse group of anaerobic microorganisms can facilitate arsenic dissolution through reduction-oxidation (redox) reactions. However, the abundance and function of cultured representatives in the groundwater environment are still unresolved. We investigated bacterial community characteristics across an arsenic concentration gradient, by amplifying and sequencing small sub-unit (SSU) rRNA genes from groundwater aquifer sediment collected at three locations, at 0.2 and 6 meter depths, along the groundwater flowpath. Analysis of sequenced clone libraries indicates that the bacterial communities at each location are diverse with up to 25 different bacterial divisions represented in 96 sequences. In addition, bacterial community structure is more similar among samples collected at the same depth than among samples at the same location. Finally, phylogenetic analysis indicates that many of the sequences generated in this study are more similar to one another than they are to sequences in genome databases. This study provides a preliminary characterization of bacterial communities in an arsenic-rich groundwater environment.

Feb. 05     Richard Yuretich, NSF Program Director, Geomorphology & Land-Use Dynamics.
"Goals and research opportunities for the National Science Foundation's Geosciences Directorate."

The mission of the Geosciences Directorate (GEO) is to support research in the atmospheric, earth, and ocean sciences. As the principal source of federal funding for university-based fundamental research in the geosciences, GEO addresses the nation's need to understand, predict, and respond to environmental events and changes to use Earth's resources wisely. The Division of Atmospheric Sciences (ATM) furthers understanding of weather, climate and the solar-terrestrial system by expanding the fundamental knowledge of the composition and dynamics of the Earth's atmosphere and geospace environment. The Division of Earth Sciences (EAR) is concerned with the structure, composition, and evolution of the Earth and the processes that govern the formation and behavior of the solid Earth. The Division of Ocean Sciences (OCE) investigates all aspects of the global oceans and their interactions with the solid earth and the atmosphere. Cross-cutting programs, special solicitations, education activities, and workforce development are also integral parts of NSF efforts to support and promote the Geosciences. The various programs at NSF GEO are eager to receive well-prepared proposals that help advance research and education in the Earth Sciences.

Jan. 29     Maureen Berlin , INSTAAR.
"Steepened channels upstream of knickpoints: Controls on relict landscape response."

The morphology of a relict landscape provides important insight into erosion rates and processes prior to base level fall. Fluvial knickpoints are commonly thought to form a leak-proof moving boundary between a rejuvenated landscape below and a relict landscape above. We argue that fluvial rejuvenation may leak farther upstream, depending on the rate and style of knickpoint migration. The outer margin of a relict landscape should therefore be used with caution in tectonic geomorphology studies, as channel steepening upstream of knickpoints could reduce the relict area. We explore the response of the Roan Plateau to knickpoint retreat triggered by late Cenozoic incision of the upper Colorado River. These knickpoints (100-m waterfalls) separate a low-relief, upper landscape from incised canyons below. We use two digital elevation model datasets to show that channels above waterfalls are steepened relative to concave channels farther upstream. The steepened reaches are several kilometers long; correspond to a two-fold increase in slope; and exhibit channel narrowing and an increase in hillslope angle. We compare two mechanisms for generating steepened reaches. The first uses a recent model for erosion amplification due to flow acceleration at the waterfall lip. The second acknowledges that waterfall lips may be limited to the outcrop of a resistant formation. Subtle structural warping of the stratigraphy can lead to lowering of the waterfall lip as it retreats, thus lowering the base level for the upstream channel. Numerical modeling suggests the latter mechanism is more consistent with our observations of long, mildly steepened reaches.

Jan. 15     Lee Stanish, INSTAAR.
"Extreme 2008: Exploration of microbial communities at hydrothermal vents in the East Pacific Rise."

Deep ocean floors, while covering a vast area of the Earth’s surface, are relatively inhospitable habitats. Extreme conditions, such as lack of sunlight, low nutrient availability, and near-freezing temperatures are the norm. Hydrothermal vents along mid-ocean ridges are areas of high geothermal activity, where hot, metal-rich waters intermingle with the ambient seawater and drive microbial metabolisms. These transient, deep-ocean hot spots harbor unique animal and microbial communities. Humans have been able to explore ocean vent communities over the past 30 years in the manned submersible, Alvin. During that time we have learned a great deal about the geologic, biogeochemical, and biological processes occurring at hydrothermal vents. Some questions remain, however, as to the role of viruses and protists in these habitats. The NSF-funded research project Extreme 2008 embarked on an expedition to answer some of those questions at the East Pacific Rise this past fall. This talk will provide an overview of the science, the Alvin experience, and some awesome footage obtained during this amazing cruise.

Fall 2008

Nov. 20     Ursula Quillmann, INSTAAR.
"CCGS Hudson Expedition 2008-029: Marine geology and paleoceanography of Baffin Bay and adjacent areas."

The HU2008-029 cruise, funded by the Canadian Foundation for Climate and Atmospheric Science and the National Sciences and Engineering Research Council of Canada, was a joint effort of the Geological Survey of Canada and the Geochemistry and Geodynamic Research Center. The objectives of the GSA were to collect high quality piston cores and high resolution seismic reflection data to (i) to sample gravity driven flows in the North Atlantic Mid-Ocean Channel, (ii) provide information for sound management of the Lancaster Sound (potential oil exploration, ship traffic through the Northwest Passage, and a proposed marine park), (iii) to investigate the 1933 earthquake on the Baffin slope, and (iv) to repeat a side scan survey from 1978 in Disko Bugt to quantify ice scours on the seafloor. The objectives of the GEOTOP group were to collect water column and sediment samples to (i) analyze the relationship between particle fluxes and ocean conditions, (ii) develop new proxies for sea-surface change, and (iii) assess climate change in the eastern Canadian Arctic and sub-Arctic.
A total of 26 piston cores, 15 box cores, 14 CTD casts, 11 plankton tows, water from 5 pumping stations, and 90 hours of Seismic Reflection data were collected from the main working areas: Davis Strait, Disko Bugt, Baffin Bay, and the North Water Polynya. The cruise stared on August 28th in Nain, northern Labrador and ended on September 23rd in Halifax, Nova Scotia. This presentation documents life and work on the Hudson, arctic scenery, wildlife, and an encounter with Hurricane Ike.

Oct. 16     David Lubinski, INSTAAR.
"Creating effective presentations: If Al Gore can do it, so can you."

Want to save time? Improve your job prospects? Help solve the climate crisis? Surprisingly, all of these can be accomplished by learning to build presentations that are memorable and drive action.

Did Al Gore become a great presenter on his own? Nope, he had a lot of help. In particular, he worked for years with a presentation design company to craft an engaging visual story. Fortunately for you, the head of that company has recently published a fantastic book called Slideology that reveals more than 20 years of company secrets.
They include (1) Don't start PowerPoint until you have already planned out your talk, its story, and its main message; to do otherwise just wastes time, (2) Take advantage of the power of the human brain to remember images; use them to help your audience SEE what you're saying, and (3) The most effective presentation might not use slides at all, it might be better to use well-crafted handouts or give a speech. Using those secrets - as well as insights from additional research - David has created a framework of tips and ideas that will make you think about talks in new ways. And, if his presentation is successful, you might just incorporate some of those new techniques in your next talk. Please come.

Spring 2008

Apr. 24     Zan Frederick, INSTAAR.
"Landscape controls on surface water solute compositions within the Yukon River Basin"

River solute chemistry is known to reflect the climate and underlying lithology of watersheds at various spatial scales. The chemical make up of large rivers is used to determine global weathering fluxes, chemical denudation, and total freshwater input to the oceans. Understanding the controls on fluxes of weathering components requires differentiating solute sources at the subbasin scale. In order to understand how landscape characteristics affect solute flux in the Yukon River Basin (YR) we examine surface water data from 43 tributaries in Alaska and Canada. Principle component analysis (PCA) based on 47 dissolved elements and ions has been applied to the major tributaries of the YR resulting in a successful reduction of data dimensionality through non-subjective groupings of variables.

We find that 7 principal components (PC) account for approximately 88% of the variance in our original variables shared by 43 tributaries. PC1 is considered a lumped mineral weathering component with loadings for both Ca2+ and HCO3-, the largest cation and anion charge contributors respectively, that it also shares a negative loading for SiO2 may reflect the dominance of carbonate weathering over silicate weathering. PC3 has a unique positive loading for sulphate and may reflect a sulfide oxidation signal. Correlating PCs with physical basin characteristics shows that the PC1 combination of variables is indicative of surface waters draining boreal Broadleaf Forests. PC2 is correlated with wetland, and permafrost distribution typical of Spruce forests, while correlations indicate that PC3 variables reflect solute chemistry from basins dominated by discontinuous permafrost, shrublands and igneous bedrock.

Apr. 17    Will Wieder, INSTAAR.
"Global warming ready? - A talk about tropical forests, the C-cycle, and potential ecosystem response to global warming"

Climate change predictions for tropical latitudes are strong, but highly uncertain. Concurrently, lowland tropical forests dominate the terrestrial C-cycle. Thus, an educated understanding of these systems are likely to respond to climate change is critical for predicting the ability of tropical forests to mitigate C change. Here we present initial results from a field precipitation manipulation in a lowland wet tropical forest. Decreasing precipitation slows rates of liter decomposition. Concurrently, while decreasing precipitation slows C and nutrient return to the soil, it also appears to decrease periods of soil anoxia and change fluxes of CO2 and N2O. These somewhat confounding results indicate that predicting ecosystem responses to future climate change deserves further investigation, especially in systems that house astounding biodiversity and play a dominant role in the terrestrial C cycle.

Apr. 10    Jeremy Smith, Dept. of Geography, CU-Boulder.
"Subalpine tree demography and climatic variation in the Colorado Front Range"

Long-term data from permanently marked tree populations are essential for evaluating the effects of recent climatic variation on tree mortality and recruitment patterns. In this study we address the temporal patterns of tree mortality in subalpine forests in the Colorado Front Range and how these patterns are associated with climatic variation. Ten permanent forest plots initially established during the 1980s in the subalpine zone in Boulder County were re-measured for mortality, recruitment, and radial growth during the summer of 2007. Each plot ranging in size from 324 to 2916 square meters contains an average of over 400 permanently tagged and mapped trees (> 4 cm dbh). Six plots represent a topographic-moisture gradient of old (i.e. > 300 years) stands at xeric sites dominated by limber pine or lodgepole pine to mesic stands of Engelmann spruce and subalpine fir. Four plots are relatively even-aged (c. 100 to 120 years old) post-fire stands of mainly lodgepole pine. To supplement the 1982-2007 data on tree mortality from direct measurements, all standing dead and fallen but preserved dead trees were cored for determination of death dates using dendrochronological methods. Tree mortality rates were highly variable at annual and decadal time scales, and higher mortality was associated with episodes of warmer and drier conditions like those recorded during the late 20th to early 21st centuries. These results contribute to the understanding of subalpine forest dynamics, particularly in the context of recent climate change.

Keywords: permanent plots, tree mortality, subalpine forest, drought

Apr. 03      Chandler Engel, INSTAAR.
"Defining geometry and force balance at Columbia Glacier, Alaska"

Eustatic sea level rise is currently dominated by ice-loss contributions, about 60% of which comes from disintegrating ice caps and glaciers. Alaskan glaciers are the major present day contributors in this category. Of these, retreating tidewater glaciers in south central and south eastern Alaska are the largest storage bodies with the most efficient mechanism for the transfer of grounded ice to the oceans, massive calving. These systems are poorly understood on many levels, which in part explains why they are often absent in climate models and some sea level rise estimations. Magnitudes of driving stresses and their resistive counterparts, basal/lateral drag and cross flow tractions are important pieces in puzzling out retreat behavior. Knowledge of the basal topography is a critical component of this analysis, but is not well characterized. A realization of the basal topography along the Eastern Trunk is defined using a continuity framework applied to observed strain rates.

! The forces acting on the glacial body are defined by balancing horizontal gravitational forces and calculated resistances from a Glen type flow law.

Mar. 20      Ty Atkins, INSTAAR.
"Surface-groundwater interactions and nutrient transport in alpine and subalpine catchments, Front Range, CO"

Nutrient fluxes from two high elevation catchments in the Colorado Front Range, Como Creek and the Green Lakes Valley, are compared across differing landscapes. These watersheds share similar climate, aspect, and geography. Como Creek primarily drains subalpine forest with little alpine area, while in contrast the adjacent Green Lakes Valley drains alpine tundra and talus slopes, before reaching the subalpine forest. Comparing NH4+, NO3-, DON, and DOC yields from Como Creek and the Green Lakes Valley from the last 30 years, show that alpine areas subsidize transport of inorganic nitrogen down gradient into forested areas. In contrast, at Como Creek there is little export of inorganic N, higher export of organic N, and much greater export of DOC compared to Green Lakes Valley. Three-component hydrologic mixing models using O18 and Na as tracers from groundwater and surface water sources show that discharge at Como Creek is characterized by a well-mixed deep groundwater reservoir with a residence time of years to decades, whereas the Green Lakes Valley discharge shows more recent water characterized by shallow subsurface flow. These distinct flow paths confirm that changes in nutrient processing in shallow soil across the alpine – subalpine ecotone control nitrogen loss in these ecosystems.

Mar. 13      Kaelin Cawley, INSTAAR.
"The impact of Dissolved Organic Matter (DOM) on the growth of Alexandrium fundyense in laboratory cultures"

Several algal species responsible for harmful algal blooms (HABs) have recently been found to be mixotrophic under certain environmental conditions. One such organism, Alexandrium fundyense, is found in “red tide” blooms which cause paralytic shellfish poisoning (PSP) in the Gulf of Maine. The ability to switch between photosynthetic and heterotrophic modes of nutrition may play a role in the timing and severity of HABs in coastal regions. Studies up to this point have linked increases in inorganic nutrient concentrations to HABs, but have been unable to develop a consistent method of predicting HABs and PSP outbreaks based solely on inorganic nutrient inputs. In this study we looked at the impact of nutrients found in dissolved organic matter (DOM) on the growth of Alexandrium fundyense cultures. DOM is a reservoir of organic forms of nutrients, like nitrogen and phosphorus. It is ubiquitous to all natural waters and plays a role in global nutrient cycling. Based on analyses of changes in DOM character in the laboratory, we hypothesize that Alexandrium uses dissolved organic matter to enhance growth in the coastal zone during HAB events.

Feb 28      Ursula Quillmann, INSTAAR.
"North Atlantic cooling and freshening at 8.2ka detected in formanimiferal Mg/Ca and δ¹⁸O ratios."

The 8.2 ka cooling event is largest climate excursion in the Holocene. This cooling event has been associated with a final, catastrophic draining of proglacial lakes Agassiz and Ojibway, which released ~163,000 km3 of fresh water into the North Atlantic (Barber et al., 1999). Greenland ice cores record a 6°C cooling, lasting ~100 years, around 8.2 ka BP. The 8.2 cooling event was widely spread (Alley et al., 1997) yet remains undetected in most high-latitude marine records. We attempt to answer if the 8.2 ka cooling event left a signal in the North Atlantic and if the 8.2 ka event manifested itself as a cooling or freshening or a combination of both.

NW Iceland was chosen as our study site for its sensitive location close to the oceanic Polar Front, the boundary between the water masses of the Irminger Current (IC) and the East Greenland Current (EGC) (Fig 1). Today the waters of the IC overlie our study site. The IC, a branch of the North Atlantic Current, carries relatively warm (~4-7°C) and saline (>35.0‰) waters northward while the EGC carries relatively cold (~0°C) and fresh (~34.4‰) waters southward. The 39-m long Calypso piston core MD99-2266 (66°13’77”N, 23°15’93”W, water depth 100 m) was retrieved at the mouth of Isafjardardjup, the largest fjord incising the Vestfirdir Peninsula, NW Iceland, as part of the IMAGES V cruise (Labeyrie et al., 2003).

We present prelimary results of Mg/Ca and d18O of the benthic foraminifer Cibicides lobatulus to detect the 8.2 ka cooling event on the Icelandic shelf. We took advantage of the high sedimentation rates of MD99-2266. A conventional sampling resolution of 100 years might not detect an event that lasted only 100 years, so we sampled at a resolution of ~15-24 years between 7700 and 8400 cal yr BP. The chronology in this interval is well constrained by 6 AMS 14C dates. We anticipated that the commonly used d18O of foraminiferal calcite, which is a function of temperature and salinity, might not have recorded the event, because a cooling would result in heavier isotopes and the freshening in lighter isotopes. We therefore also analyzed the Mg/Ca ratio of foraminiferal calcite, which appears to be a function solely of temperature. We chose Cibicides lobatulus, a benthic, epifaunal foraminifera that occurs in high percentages in the core, for both d18O and Mg/Ca analyses. We used the results of Mg/Ca to quantitatively reconstruct temperature, but first we had to calibrate the Mg/Ca of C. lobatulus against temperature. Our provisional calibration curve for the Mg/Ca of C. lobatulus against temperature (T), Mg/Ca=1.10+0.129 T, which is based on the analysis of 12 shallow (100-350 m) surface sediment samples from the SW/N Iceland and Greenland shelves with a robust temperature data set ranging from 0.6-7.2° C. During the 8.2 ka event the d18O of C. lobatulus composition became heavier by 0.2‰, which would indicate a ~1°C cooling if due to temperature alone. The temperature reconstruction based on the Mg/Ca analysis showed a ~3°C cooling at 8.2 ka, lasting ~100 years (Fig 2). We used these results to obtain the salinity contribution in the d18O by calculating the d18O of seawater using the Lynch-Stieglitz (2003) Cibicides equation: d18O(foraminifera)- d18O(seawater)+0.27=-0.21T+3.38. The results showed a lighter d18O of seawater composition by ~0.4‰. We estimate that a 0.4‰ change in the d18O of seawater corresponds to roughly a ~0.5-1.0 ‰ change in salinity. Two different scenarios could explain the mechanisms for the cooling and freshening that our proxies see on the NW Icelandic shelf. The first scenario is that the freshwater from the outburst was entrained into the waters of the North Atlantic Current and subsequently into the IC and lowered the overall salinity of the North Atlantic. The second scenario is that more water from the EGC reached our study site. The difference in salinity between the two currents is about 0.7‰ today.

See several figures at: http://instaar.colorado.edu/meetings/AW2008/abstract_detail.php?abstract_id=49

Feb 28      Adina Racoviteanu, INSTAAR.
"Debris-cover mapping in Sikkim (Kanghendzonga area), Indian Himalayas using Aster imagery."

There is urgency in developing and testing remote sensing tools for developing extensive glacier datasets in high altitude areas of the Himalayas. One of the biggest challenges in glacier mapping from spaceborne imagery is the delineation of debris-covered glacial tongues. The high Himalayas provide interesting challenges and unique opportunities for testing debris-cover mapping algorithms. This research exploits the potential of visible, infrared and thermal ASTER data combined with terrain parameters for mapping of debris cover in the Himalaya. I developed a decision tree using a combination of multi-spectral classification techniques (ASTER ¾ band ratios and normalized differences NDSI and NDVI), topographic characteristics (elevation and slope), thermal information, color transformations and spatial analysis capabilities of GIS. The test site is the Sikkim Himalayas, with a focus on the larger Zemu and Talung glaciers.

Feb. 21      Christophe Randin, INSTAAR.
"Climate change impact on plant distribution in the Swiss Alps: lessons from the past and simulations for the future."

Due to their conic shape and the reduction of area with increasing elevation, mountain ecosystems were early identified as potentially very sensitive to global warming. Moreover, mountain systems may experience unprecedented rates of warming during the next century, two or three times higher than that records of the 20th century. Results of monitoring of past vegetation changes suggested that plant species can react quickly to the warmer conditions on alpine and nival summits as far as competition is low. However, in subalpine grasslands, competition of already present species is probably important and limit establishment of newly arrived species. In this context, species distribution models (SDM) have become important tools for rapid assessment of the impact of accelerated land use and climate change on the distribution of plant species.

In my previous studies, I first developed and tested new predictor variables for SDM, specific to geographic projections of plant species in a mountain system, using the Western Swiss Alps as a model region. Since meso- and micro-topography are relevant to explain geographic patterns of plant species in mountain environments, I also assessed the effect of scale on predictor variables and geographic projections of SDM. Then I developed a methodological framework of space-for-time evaluation to test the robustness of SDM when projected in a future changing climate. Finally, I used a cellular automaton to run dynamic simulations of plant migration under climate change in a mountain landscape, including barriers and realistic distance of seed dispersal. Results of future projections for the 21st century were discussed in perspective of vegetation changes monitored during the 20th century.

Overall, I showed that, based on the most severe A1FI climate change scenario (derived from the HadCM3 GCM) and the most realistic simulations of plant dispersal, complete extinctions in the Western Swiss Alps could affect nearly one third (28.5%) of the 284 species modeled by 2100. With the less severe B1 scenario, only 4.6% of species are predicted to become extinct. However, even under B1, 54% (153 species) may still loose more than 80% of their initial surface. Under all climate change scenarios, the proportion of species losing their habitat was particularly high for short dispersal species, alpine species and for high-elevation growth forms, such as cushion plants, dwarf and prostrated shrubs.

Jan. 31      Kathrin Lang, INSTAAR.
"Ozone flux measurements over the ocean."

Ozone is a toxic and highly oxidative gas. In the atmosphere, its role is altitude dependent. Stratospheric ozone protects the Earth’s surface from dangerous UV-radiation and makes life livable on earth. However, tropospheric ozone impacts human and animal health, plant growth and is an important greenhouse gas. The contribution of tropospheric ozone to anthropogenic greenhouse gas forcing is about 13% and therewith it is the third most important greenhouse gas after CO2 and methane. This indicates a doubling of tropospheric ozone since industrialization, and thus further investigations are required.

The oceans as a sink are of interest since they cover 70% of the earth surface and have a significant impact on the global ozone budget. Flux data are obtained by th eddy covariance techniques and resulting deposition velocities are used in global atmospheric chemistry models like ECHAM4/Messy (European Center Hamburg Model/Modular Earth Submodel System) or MOZART-1 (Model for Ozone and Related Chemical Tracers) to predict future ozone concentrations, its effect on climate and to estimate the global ozone budget. In literature, values for the deposition velocity range from 0.01 to 0.12 cm s-1 for ocean water.

This talk will give an introduction to the eddy covariance technique and present data and results of the “Gulf of Mexico and East Coast Carbon Cruise 2007” (GOMECC), which took place from 07/10/07 to 08/04/07 and went from Galveston, TX to Boston, MA.

Jan. 17     Molly Brodin, INSTAAR.
"Ground-level ozone pollution in Boulder County."

The Denver Metro Area, which includes Boulder County, was recently designated by the Environmental Protection Agency to be in non-compliance with National Ambient Air Quality Standards for surface ozone. Such a large urban area situated in a mountain-plains transition zone offers many unique opportunities for the study of ozone sources and transport. This presentation will introduce an ongoing monitoring project in Boulder County, which includes 12 ozone monitoring sites and spans the elevation gradient from downtown Boulder to the top of Niwot Ridge.

Fall, 2007

Dec. 06      Maureen Berlin
"Relict landscape response to knickpoint migration on the Roan Plateau, western Colorado, explored through ALSM data analysis."

Berlin, M M and Anderson, R S

The unprecedented spatial resolution of Digital Elevation Models (DEMs) derived from Airborne Laser Swath Mapping (ALSM) makes them ideal for detecting subtle morphologic features. We explore to what extent information about knickpoint migration is communicated upstream by analyzing an ASLM-derived DEM in a transient landscape. We target the Roan Plateau in western Colorado, a landscape developed in flat-lying Eocene shales, in which multiple upstream-migrating waterfalls triggered by base level fall have incised dramatic canyons in their wake. The waterfalls separate low-gradient, bedrock-floored reaches above the waterfalls from steep, boulder-choked canyons below. Similarly, a sheer canyon rim separates a smooth, relict landscape above the canyon walls from the steep cliffs and talus-mantled slopes below. Waterfall and canyon rim elevations correlate well with the outcrop of a resistant oil-shale layer. We use a 1-meter DEM to develop two simple metrics that detect channel and hillslope response of the upper landscape to knickpoint migration. The first metric is stream profile analysis of upper plateau tributaries. In a steady-state stream channel, slope should decrease with distance downstream, as drainage area and the associated water discharge increase. Departures from this trend can be attributed to either lithologic variation, or transient oversteepening that may be associated with the presence of the waterfall. Oversteepening of the channel can incite hillslope response, and give rise to a box canyon upstream of the waterfall. We document the slope of channels as they approach the free overfall, and the presence and lengths of box canyons upstream of the waterfall lip. The second metric is the curvature of plateau hilltops. In a steady state landscape, hilltops should be roughly parabolic in cross-section, reflecting a balance between a uniform rate of regolith production and diffusive transport at all points along the hillslope. Departure from this parabolic form can reflect lithologic variation, transient hillslope response to increased rates of stream incision, or transport processes that are not linearly dependent on slope. Isolation of roughly the upper 100 m of hilltops and evaluation of the curvature of these crests provides constraint on the ratio of weathering rate to transport efficiency in the landscape most likely to be in steady state. Changes in crest curvature with distance from the canyon rim can be used to document transient hillslope response of the upper plateau surface in areas with uniform lithology. Paired with field observations and mapped bedrock contacts, analysis of an ASLM-derived DEM allows us to evaluate the extent to which the upper plateau channels and hillslopes have responded to knickpoint migration and the carving of canyons downstream. Morphologic evidence for significant upper plateau response to this incision event would suggest that the timescale for landscape adjustment to base level fall may be shorter than that required to propagate a knickpoint upstream.

Dec. 06     Ken Hill
"Hydrochemical response to drought conditions at an alpine watershed, Colorado Front Range."

Kenneth R Hill, Mark W. Williams, Nel Caine, Jason R. Janke, and Melannie D. Hartman

Extreme climate events play a key role in alpine hydrochemistry by altering source waters and flowpaths. Persistent drought conditions from 2000-2002 at Green Lakes Valley resulted in precipitation and streamflow about 60% of normal for the last 25 years. Surprisingly, both concentrations and fluxes of geochemical weathering products and nutrients increased during the drought at the higher elevation sites. Niwot Ridge LTER has continuously monitored streamflow, precipitation chemistry, and water quality for 25 years in Green Lakes Valley at 8 sites representing an elevation gradient extending from 3250 meters at the valley outlet to 4000 meters at the continental divide.

Comparing continuous 5-year blocks of above-average precipitation (1993-1997) vs. below-average years (2000-2004), both concentrations and fluxes were significantly higher during drought for base cations (p<0.05) and Nitrate (p<0.10) throughout upper Green Lakes Valley. DAYCENT modeled predicted discharge correctly during the period of above-average precipitation but underpredicted discharge during drought conditions, suggesting an additional source of water.

End Member Mixing Analyses (EMMA) conducted during 1996 constrains streamflow as a mixture of snowmelt, talus water, and groundwater with subsurface flowpaths contributing more than 50% of streamflow, even during snowmelt (Liu, 2004). However, EMMA results during drought years using chemical and isotopic compositions from surface water, talus springs, snowpits, snowmelt, soil water, and groundwater suggest an additional, unidentified source of streamflow.

One possible end member is melting permafrost within the basin. We downscaled a qualitative, regional permafrost distribution model of the Colorado Front Range to investigate the potential role of melting permafrost on hydrochemical characteristics in Green Lakes Valley. Model results indicate that increasing mean annual air temperature by 1° C results in a 33% decrease in probable permafrost by area. Future monitoring and research efforts will examine the potential irreversible effects of extreme climate events and permafrost melt on alpine ecosystems.

Dec. 06     Brian Seok
"Carbon Dioxide gas exchange through the snowpack and its contribution to the ecosystem carbon budget in a high-elevation, subalpine forest."

Brian Seok, Daniel Liptzin, Kurt Chowanski, Jacques Hueber, Mark Williams, and Detlev Helmig

Snow cover significantly affects microbial activity in the soil underneath by influencing both respiration and soil nitrification and denitrification processes. Past studies have shown how this can alter ecosystem carbon budgets as climate change continues. In our project, we measured winter carbon flux from the soil through the snowpack near treeline at a 3345 m asl site, an open meadow surrounded by ribbon forest, in the Niwot Ridge Long-Term Ecological Research Site in the Colorado Rocky Mountains for 3 winter seasons (2004 – 2006). Fick’s law of diffusion was applied to calculate the carbon flux from measurements of gradients in gas concentrations and snowpack density. We also analyzed the influence of wind-pumping (or pressure-pumping) on carbon flux calculation, which Fick’s law ignores. Generally, flux calculations using Fick’s law without incorporating wind-pumping effects gave us an underestimate of the true carbon flux.

We measured maximum snow depth at our study site to be 1.9 m in 2005 and 2.1 m in 2006. The total wintertime seasonal CO2 loss was 8.89 mol m-2 for 2004 and 7.48 mol m-2 for 2005. These values are about 2 times larger than those observed at a lower elevation (3021 m asl), flux tower approximately 3 miles from our site (4.03 mol m-2 from 2003 winter season)1,which is within a closed canopy forest dominated by subalpine fir, Engelmann spruce, and lodgepole pine.

This and similar research presented previously have been done in high altitude alpine regions. We are now continuing our work at the University of Michigan Biological Station Ameriflux site, which is a low elevation (219 m asl) lake-side region near Pellston, MI to further study the environmental factors that determine the CO2 gas exchange through the snowpack.

1 Monson, R. K., S. P. Burns, M. W. Williams, A. C. Delany, M. Weintraub, and D. A. Lipson (2006), The contribution of beneath-snow soil respiration to total ecosystem respiration in a high-elevation, subalpine forest, Global Biogeochem. Cycles, 20, GB3030, doi:10.1029/2005GB002684.

Nov. 29      Tisza Bell, INSTAAR.
"Balsam fir leaf litter extract stimulates growth of the green snow alga Chloromonas rosae var. psychrophila (Chlorophyta, Volvocales) from Whiteface Mountain, New York."

Chloromonas rosae var. psychrophila is the dominant snow alga at Whiteface Mountain, New York, and balsam fir needles often cover the snowbanks in which it lives. Two strains of this snow alga, CU 204 (UTEX SNO 11) and CU 479A (UTEX SNO 56), were isolated from Whiteface Mountain into axenic culture and were grown in balsam fir leaf litter extracts at varying concentrations over a four-week period. Each strain grew better when extract was added to defined modified M-1 medium (control) at all concentrations tested (200:1, 100:1, 50:1, and 25:1; medium:extract) with best growth at 100:1. In strain CU 479A, there was less growth in the highest extract concentration (25:1) when compared to the other concentrations of extracts employed. Both strains showed an increase of growth over a 28-day period when results were pooled for each extract concentration. The results of these experiments suggest that balsam fir leachates stimulate the growth of this snow alga in nature, which may be a selective advantage.

Glacial landforms deposits from the last glacial maximum are generally well preserved in arctic and alpine regions, and these features allow us to reconstruct the extent of paleoglaciers and ice sheets, probe climate variability on a glacial-interglacial timescale, and explore how glacial processes have modified the landscape. Glacial deposits from earlier glacial advances are more rarely preserved and are often exposed only in limited outcrops. However, these older deposits contain valuable information about glacier and ice sheet dynamics and landscape evolution over much longer timescales. This talk will describe two topics of ongoing research in these areas: (1) identifying late-Pleistocene moisture sources affecting the Sangre de Cristo Mountains of southern Colorado through paleoglacier equilibrium line altitude reconstructions, and (2) using a ca. 2.5 Ma-long record of glaciomarine sediments from Baffin Island to evaluate possible changes in the dynamics of the northeastern part of the Laurentide Ice Sheet through successive glaciations.

Nov. 08      Adam Eisele, INSTAAR.
"Into Thin Air: A personal account of the epic air toxics tale in Boulder County"

Boulder County sits at the confluence of the pristine high alpine wilderness of the Rocky Mountains, the heavily urbanized city of Denver, Colorado, and the agricultural and intensive oil and gas activities in neighboring counties. This urban/rural interface creates a complex air quality environment characterized by shifting upslope and downslope air flow conditions that can intensify air toxics in relatively pristine environments. This is evidenced by the regional ozone concentrations which often peak in the foothills, not in the metro area or east of Denver. Therefore, Boulder County Public Health and its partners are monitoring volatile organic compounds, carbonyls, and ozone at five locations around Boulder County to aid in air toxics model evaluation and air toxics source apportionment. Timely carbonyl and tracer gases will enable the county to better assess the impacts from primary and secondary air toxics pollutant sources in the urban-mountain interface. In addition to developing a baseline reference for longer-term air toxics monitoring, this project will evaluate and improve air quality exposure models and guide air quality management strategies in Boulder County.

Oct. 18      Adina Racoviteanu, INSTAAR.
"Are the Andean mountain Gods upset? Glacier and climate changes in the Cordillea Blanca of Peru inferred from remote sensing and field data."

We present a new geospatial inventory for the Cordillera Blanca of Peru (8°30 S, 77°W), constructed from 2003 SPOT5 satellite data. Here we focus on spatial patterns of glacier fluctuations at decadal scales and changes in glacier parameters (glacier area, termini elevations, median elevations and hypsography). Based on two previous estimates of ice extent in 1970, we calculated a loss in glacier area of -14 to -22% from 1970 to 2003 (-0.4 to -0.6% per year). Glacier termini elevations rose by +113.4m and median elevation rose by +65.5m respectively, with bigger increases on the wetter Eastern side. Glaciers throughout the study area show signs of disintegration implying a down-wasting trend, along with a shift of glacier ice to higher elevations. The rate of glacier change is consistent with trends noted in the last three decades in the Andes and elsewhere. The SPOT5-derived datasets are in public domain in the Global Land and Ice Measurements from Space (GLIMS) Glacier Database (www.glims.org) maintained at the National Snow and Ice Data Center (NSIDC) in Boulder.

Sep. 13      Maureen Mason Berlin, INSTAAR.
"Feedbacks between sediment supply and channel evolution following knickpoint retreat in canyons on the Roan Plateau, western Colorado."

Co-author: Robert S. Anderson

Canyons downstream of multiple knickpoints on the Roan Plateau provide a unique opportunity to explore feedbacks between sediment supply and channel evolution in a transient landscape. We have previously explored the pattern of knickpoint retreat, initiated by late Cenozoic incision of the Colorado River, with a kinematic model in which the retreat history of each knickpoint is a power-law function of its declining upstream drainage area. We now make use of the strong similarity in shape between canyon planforms and channel longitudinal profiles downstream of knickpoints, well documented using LiDAR 1-m and USGS 30-m digital elevation data, to develop and test a model for channel evolution. Morphologic self-similarity requires that retreat of the canyon walls be tied to lowering of the channel profile. We ask how the bedrock channel profile and alluvial thickness distribution are maintained in the face of the sediment supply this linkage demands. We employ a simple numerical model founded upon conservation of sediment: the rate of change of alluvial thickness at a point is the sum of the sediment supplied from retreat of canyon walls, the loss of sediment (to solution or suspension) by weathering, and the divergence of sediment (bedload) transport. Consistent canyon width-to-depth ratios (typically ~2.5) allow us to scale canyon wall retreat rates to local channel incision rates. We assume higher weathering rates closer to each knickpoint, where waterfall misting is greatest and any loss of water discharge to infiltration is minimal. Bedload sediment transport scales with excess shear stress. Changes in sediment thickness modify both the channel slope and the protection of the bedrock channel floor, providing a feedback mechanism that either enhances or reduces the channel incision rate (and hence canyon wall retreat rate), depending upon the channel incision rule employed. Model iterations are evaluated by their ability to predict observed canyon planforms and longitudinal channel profiles, estimates of sediment thickness, and knickpoint retreat histories consistent with our previous modeling of multiple canyons. Our approach therefore marries detailed topographic data with numerical models, allowing quantitative testing of the effects of sediment supply on transient longitudinal profile evolution.

Spring, 2007

Apr. 19        Larry Bowlds, INSTAAR, Managing Editor of Arctic, Antarctic, and Alpine Research.
"Beyond peer review: the other part of the editorial process."

After the data have been gathered and interpreted and the rough draft has been written, there are many facets involved with the publication process besides peer review. This talk will focus on four parts of that process. First, selecting a journal involves the journal's focus, readership, costs, manuscript backlog, and publication delay. Second, after selecting a journal, the manuscript should be written or adapted to meet the journal's requirements, including everything from using the correct word-processing software to following the journal's style rules. Figures require special attention. Third, manuscript submission can be a frustrating experience unless the author understands the journal's time delays associated with review. Prompt revision of the manuscript, accompanied by detailed notes, can accelerate the manuscript's progress toward acceptance. Fourth, the most time-sensitive part of the process comes after acceptance. The editor requires access to the author at all times, the time schedule set by the printer is rigid, and the author must read everything word-for-word more than once. When the paper has finally been published, the author should always ask for a PDF.

Apr. 12       Zan Frederick, INSTAAR
"The Yukon, The USGS and Me."

I will present a geographic overview of the Yukon River basin and give an introduction to the USGS NASQAN water quality study which began on the river in the fall of 2000. The Yukon River extends ~3400 km from its (disputed) headwaters in British Columbia to the Bering Sea, flowing through a basin of over 850,000 km^2. The USGS has maintained a continuous discharge record of the Yukon River near the international boarder with Canada beginning in 1950. Since that time, between 400 and 500 gaging stations (USGS proprietary spelling reserved) have been operated discontinuously throughout the basin. In 2000, the USGS National Research Program (NRP) and the Water Discipline of the Alaska Science Center began a cooperative study aimed at monitoring and establishing baseline water quality data for the Yukon River and some 40 of its tributaries. This study was initiated as part of the broader research agenda of the USGS National Stream Quality Accounting Network (NASQAN) to assess the impacts of a warming northern climate.

I was hired as a field hydrologist by the Yukon River group in the spring of 2002 and spent 4 summers working on the Yukon as part of the field campaign. I will present photos and stories from the study, the findings of some recent publications, and the direction I intend to pursue during my graduate research

Apr. 05      Lee Stanish, INSTAAR
"Diatom community composition in Antarctic freshwater streams: past, present, and future."

Diatoms are micro-algae that are abundant in marine, freshwater and terrestrial ecosystems and contribute significantly to global primary production. Diatom species assemblages reflect environmental conditions, making them useful ecological indicators. In addition, they produce bipartite silicate shells that remain in sediments and can be used to reconstruct past climates.

In the McMurdo Dry Valleys of Antarctica, stream diatoms present an oasis of diversity relative to the harsh, barren desert ecosystem. They exist within benthic cyanobacterial mats overlying the stream bed and become active during the austral summer, when the streams are fed by glacial runoff and hyporheic seepage. This harsh environment leads to high rates of endemic species, with 24 of the 40 documented species not found outside of Antarctica. Recently, Esposito et al. (2006) found a strong relationship between stream harshness and diatom diversity such that more harsh environmental conditions increase relative abundance of endemic diatoms, and that species diversity peaks when the assemblage consists of 40-60% endemics. This finding raises the question of potential impacts to diatom diversity in Dry Valley streams if warmer temperatures lead to less harsh conditions.

This talk will introduce some of the approaches that will be used to better understand the ecology and evolution of Dry Valley stream diatoms. Algal mat samples were collected during the 06/07’ field season as part of the MCMLTER project. These samples will be used for multiple purposes, including: constructing molecular phylogenies from ribosomal RNA; incorporating more data into the findings of Esposito et al. (2006) and refining the harshness index; and developing molecular species markers for Dry Valley stream diatoms.

Mar. 22      Kurt Refsnider, INSTAAR
"Late Pleistocene alpine glaciation in the Uinta Mountains: The importance of precipitation variability on glacier chronologies."

The Uinta Mountains of northeastern Utah were glaciated repeatedly during the Pleistocene, and glacial deposits from the Smiths Fork and Blacks Fork glaciations (Pinedale and Bull Lake equivalents, respectively) are well preserved throughout the range. Reconstructions of Smiths Fork ice extents suggest that the central and eastern parts of the range contained discrete valley glaciers, ranging from 4 to 43 km in length. However, valleys in the extreme western end of the range, which is lower in elevation than the central part of the range, were occupied by outlet glaciers of the 685 km2 Western Uinta Ice Field. Equilibrium line altitudes (ELAs) in this part of the range were ca. 2600 to 2800 m asl, whereas ELAs in the central and eastern parts of the range were generally above 3000 m asl. This pattern of glaciation in the Uintas suggests that winter precipitation in western valleys nearest pluvial Lake Bonneville (~50 km upwind; 19-16 ka) was enhanced relative to valleys located farther east.

Initially, to test this hypothesis, we obtained cosmogenic 10Be surface-exposure ages of terminal moraine boulders from across the Uinta Mountains. Exposure ages from the southwestern Uintas reveal that ice in the Lake Fork valley remained at its maximum position until 16.8 ¬± 0.7 ka, nearly 2 kyr later than when glaciers in the neighboring Wind River Range and the Colorado Rocky Mountains began to retreat. At the western end of the range, 10Be surface-exposure ages from boulders on two end moraines deposited by the Bear River Glacier, which flowed northward from the Western Uinta Ice Field, indicate that the maximum ice extent was reached by 17.9 ± 0.6 ka, and retreat likely began by 17.8 ± 0.5 ka ka. Additionally, outlet glaciers in the Provo River drainage, flowing southwest from the ice field, reached their maximum extent by 17.4 ± 0.5 ka. Paired 10Be and 26Al surface-exposure ages from striated bedrock formerly located under the center of the ice field suggest thatdeglaciation occurred by 14.0 ± 0.5 ka. However, due to shielding by snow cover, these ages provides only a minimum constraint on the timing of deglaciation of the western part of the range, which likely occurred at least 1,000 years prior to the apparent exposure ages.

Thus, the onset of ice retreat throughout the western Uintas occurred at similar times, and the collapse of the Western Uinta Ice Field may have occurred over a period of less than 2-3 kyr that was coincident with the climate-driven regression of Lake Bonneville from the Provo shoreline (~ 16 ka). These findings, along with the pattern of ELAs in the Uintas, suggest that although the lake and local glaciers were presumably responding the same regional climatic forcing, the presence of the lake amplified the extent of ice in areas immediately downwind, perhaps by providing lake-effect moisture to glacier accumulation zones. The results of simulations using a physically-based, numerical mass- and energy-balance and glacier flow model also support the hypothesis that precipitation in the western Uinta Mountains was enhanced by pluvial Lake Bonneville during the last glaciation.

Mar. 15      Lesleigh Anderson, USGS
"Exploring the secrets of the mud: Arctic and alpine lake sediments as paleoclimatic archives."

Signs of recent warming in Arctic and Alpine regions are raising concerns about the detrimental effects on permafrost, surface and sub-surface hydrology, terrestrial vegetation and the consequences for carbon storage and water resources. Although ongoing monitoring efforts are documenting clear signs of recent environmental changes, we still have a limited perspective on how climate and associated impacts on the landscapes have varied in the past. A long-term perspective is needed to better understand and anticipate the impacts of future climate change on terrestrial, cryo- and hydrologic processes. We can use indirect proxies of climatic and environmental change from lake sediments to extend records from the present back to the early Holocene (~10,000 yrs before present). Lakes are abundant in high-latitude and high-elevation locations. Sedimentary materials preserved in lakes document climatic and hydrologic variations from annual to millennial time scales. Multiple indirect climate proxy studies on lakes distributed throughout Arctic and alpine regions allow a more complete understanding of natural climatic variations and regional landscape responses. This presentation will cover how paleoclimatic investigations utilizing lake sediment are carried out, including general discussion of lakes, watersheds and sedimentation, field work (site selection, coring and sampling techniques), chronologies, data analyses and paleoclimatic interpretations.

Mar. 08      Steve DeVogel, INSTAAR
"Timing and cause of extinction of the Elephant Bird (Aepyornis) in Madagascar."

Madagascar rifted from Africa more than 100 million years ago. Since that time, evolution has gone to work creating a unique flora and fauna on the island. Humans colonized the island only about 2000 years ago. Following a millennium of human occupation, all animals on Madagascar with body mass >12 kg (except the crocodile) became extinct, including the large flightless bird called the Elephant bird (Aepyornis) and an ostrich-size bird, Mullerornis. Aepyornis was a giant at 3 m tall and weighing 400 kg. Aepyornis has the distinction of laying eggs larger than those of any dinosaur (in excess of 30 x 20 cm, and nearly 4 mm thick). Along the semi-arid southern coast, fragments of these eggs cover sand dunes in a pavement and can be found in situ in many localities. By sampling this relatively ubiquitous sub-fossil resource, we aim to answer the question of why Aepyornis became extinct. Was it driven by climate, direct overhunting, or perhaps an anthropogenic ecosystem change? A chronology of these Holocene egg fragments will be developed with radiocarbon dating creating a framework and amino acid racemization dating as an inexpensive tool to fill in the dataset and to screen for the probable youngest samples, thereby potentially pinpointing the time of extinction. Isotopes of diet (δ13C, δ15N) extracted from the dated samples will reflect potential dietary changes in response to an environmental shift in the Holocene. Additionally, potential moisture stresses due to a change or decrease in available drinking water will be recorded in the δ18O of eggshell carbonate. Previous work has shown that Aepyornis primarily ate C3 vegetation, but their eggs are found among CAM vegetation, which has a very different δ13C signal. Therefore it seems likely that they were migrating to the southwestern and southern coasts of Madagascar for breeding. Using 87/86Sr we can test the hypothesis of migration, as their diet and drinking water will introduce a Sr signal unique to the local geology from where they lived. The scientific approach described above has a track record of success in Australia (Miller et al, 2005), but here has the advantage of increased dating precision. Human-induced landscape change as a cause of extinctions is certainly a modern problem. This project has the potential to show that this problem is millennia old.

Mar. 01      Dylan Ward, INSTAAR
"Signatures of glacial erosion and retreat in the landscape: cosmogenic and numerical modeling constraints."

The response of glaciers to past climatic change is important for understanding 1) observations of modern glaciers under currently changing climate conditions, and 2) long-term effects on the landscape of repeated glacial occupation and retreat. The complex dynamics of these systems require that multiple lines of data constrain models of glacial behavior and erosion. Toward this end, we use cosmogenic 10Be exposure ages to constrain numerical simulations of glacier advance and retreat histories in the Middle Boulder Creek drainage, Colorado Front Range, and the Animas River valley, San Juan Mountains, Colorado.

We present 14 new cosmogenic radionuclide (CRN) exposure ages from glacially polished bedrock sampled in the Middle Boulder Creek valley. All of these ages are younger than a ~17 ka 10Be terminal moraine age reported by Schildgen and Dethier (2002). Ages appear to decrease monotonically with distance upvalley from the moraine, and the youngest ages in the uppermost valley are uniformly ~13 ka. We include 5 10Be ages in a cross section across the mid- valley, which demonstrate a pattern of post-Last Glacial Maximum (LGM) ages (11-16 ka) within the glacial footprint, and older, un-reset exposure ages (~40 ka) near the trim lines.

A similar age trend is seen in the Animas River valley in southwestern Colorado, which was occupied by a lobe draining the large LGM ice sheet capping the San Juan Mountains. Deglaciation began here ca. 19.4 ka, based on a 10Be depth profile in a Pinedale-age proglacial terrace. A longitudinal transect of exposure ages derived from glacially polished samples indicates that terminus retreat was relatively steady at ~15 m/yr until complete deglaciation around 12.3 ka. Neither valley has obvious recessional deposits within the LGM glacial footprint.

While the first-order trend in each valley is a monotonic glacial retreat, there are other possible retreat scenarios. For instance, we would like to test whether the same trend in 10Be concentrations could be generated by episodic retreat punctuated by periods of readvance. Each of these scenarios has different implications for the response of valley glaciers to climatic change.

To investigate these scenarios, we modified the GC2D 2D numerical glacier simulation (see Kessler et al., 2006) to incorporate a CRN accumulation layer. This layer can contain any starting value of CRN concentration, and production over each timestep is scaled to latitude and altitude (from the DEM). Topographic shielding is accounted for by calculating the horizon for each point on the DEM and passing it through the CRONUS skyline shielding calculator. Production is taken to be zero in areas covered by more than 10 m of ice.

The CRN inventory can also decline due to glacial erosion. We incorporate a selectable glacial erosion rule based on basal sliding velocity, total ice velocity, ice discharge, ice power, or basal shear stress, and calculate the reduction in CRN inventory by the depth stripped in each timestep.

We then simulate a glacier responding to equilibrium line altitude (ELA) changes imposed stepwise, gradually, or scaled to the GRIP δ18O record. Each scenario generates a pattern of ages in the CRN layer that can be compared with the map pattern of measured 10Be concentrations. Preliminary results show that a step- function ELA rise to its present value causes a retreat that is far too rapid to explain the range of ages observed in both valleys. A steady ELA rise can replicate the monotonic age trend, while an episodic retreat with readvances results in several "domains" of similar ages within the LGM glacial footprint.

Feb. 15      Alexandra Sinclair, INSTAAR
"Ocean Observatories Initiative: A revolution in ocean science."

The National Science Foundation's Ocean Sciences Division has developed the Ocean Observatories Initiative (OOI) to provide the ocean sciences research community with the basic infrastructure required to make 24/7/365, long-term and adaptive measurements in the oceans. The OOI is the result of several years of scientific community planning efforts and is now beginning to be realized. Once fully implemented, the ocean observatories will allow unprecedented monitoring of geological, physical, biological, chemical, and geophysical processes. This grad talk will address the following:

- What is the Ocean Observatories Initiative?
- Where are the observatories located or planned to be located?
- What scientific questions are best answered with ocean observatories?
- What is the applicability to INSTAAR research areas?
- Spotlight on NEPTUNE, a regional cabled observatory
- The big, long-term vision for integrated ocean observatories

Feb. 08      Adina Racoviteanu, INSTAAR
"Glaciers, rishis and pilgrimages: Experiences from a solo field season in
the Indian Himalayas. "

Glaciers in mid-latitude areas of the world are important for water resources and sensitive indicators of changes in climate. The importance of mountains as water resources is recognized in ritual practices in the high Himalayas. For Hindus, Dudh Kunda (Milk Lake) at the base of the sacred mountain Shorung Yul-lha (Numbur) in the Solu region of Nepal is a site of a yearly pilgrimage and purifying ritual bathing. In India, pilgrims gather at the Gangotri, the source of the holy Ganges, to worship the glacier. Accelerated glacial retreat observed throughout the Himalayas in the last two decades, poses a threat for local water resources and glacier-related hazards.

There is a paucity of glacial information in many of the high-mountain areas of Asia because of the difficulty of conducting field campaigns in rugged terrain, lack of logistical support and political or cultural conflicts. Data on glacial metrics from heavily glacierized areas such as the Tibetan Plateau, Northern Himalaya and Hindu-Kush are almost completely missing from mass-balance records. The present research fills this gap by using ASTER imagery, GIS and field methods to assess glacier change and climate forcing across the Himalayas from the basin scale to the regional scale.

During Sept – Dec 2006, I conducted my first field campaign in the Himalayas. I also participated in a joint field campaign on Chhota Shigri glacier (in the Lahaul-Spiti district of the Indian Himalayas), organised by the French IRD (Institut de Recherche pour le Développement) in collaboration with the Glacier Research Group at JNU (Jawaharlal Nehru University), India. The main objective of the 2006 field campaign was to continue traditional field-based glacier measurements needed for mass-balance estimations. An additional objective was to acquire ground control points (GCP’s) needed for orthorectification of ASTER imagery. Surveyed sites included: Nanda Devi area (Kumaon), Gangotri (Himachal Pradesh) and Sikkim Himalayas. This research is funded by a NASA Earth System Science Fellowship.

This talk is a visual journey through the Indian Himalayas: people, glaciers, pilgrimages, bone-rattling bus rides, high peaks and holy sites. A glimpse of both the beauty and challenge of doing research in the Indian Himalayas.

Jan. 18      Ursula Quillmann, INSTAAR
"Holocene environmental variability in Isafjardardjup and its tributary fjords, NW Iceland."

Three marine sediment cores from Isafjardardjup and its tributary fjords (water depths ~100 m) were analyzed for sedimentological parameters, foraminiferal assemblages, and light stable isotopes to obtain a detailed record of Holocene environmental variability. AMS14C dates and the depth of a tephra layer of known age constrain the age models. Glacial marine conditions prevailed until ~10,100 cal yr BP, when tide water glaciers stopped calving and depositing ice rafted debris. Other studies suggested a lowering of relative sea level (RSL) on the order of 40 m in response to glacial unloading and isostatic rebound in NW Iceland. A lowering in RSL would explain the warming and increased bottom current strength of a shallower water column that is evident in the relatively light ?18Ocalcite values and the presence of strong bottom current indicating species, such as Cibicides lobatulus, Astronion gallowayi, and Elphidium albiumbilicatum f. clavata, in Skotufirdir (a tributary fjord). At the mouth of Isafjardardjup, the lower RSL would explain the increased mass accumulation rates, where shallow banks became subject to increased erosion. High insolation and the influx of the warmer, more saline water masses of the Irminger Current (IC), which replaced the colder, fresher water masses of the East Greenland Current, contributed to the warm signal of the early Holocene (~10,600/10,100 – 7000 cal yr BP). The warm signal was truncated at 8900 cal yr BP in Skotufirdir. Overturning of the water column occurred when surface waters cooled sufficiently during the long polar night and became denser than the underlying water masses. Arctic bottom waters support an arctic fauna at the site despite the presence of warmer IC waters during the summer. Insolation became the more evident driver for climatic variability once glacial activity had ceased and no longer obscured the proxy record. The onset of Neoglaciation was noted ~2700 cal yr BP. Shifts in the isotopic composition of organic carbon and the carbon nitrogen ratio over the last 2000 years suggest that increased soil erosion was caused by deteriorating climate and not farming after the settlement of Iceland in AD871.

Fall, 2006

Dec. 07        Jessica Black , INSTAAR
"Diatoms as proxies for a fluctuating Holocene ice cap margin in Hvitarvatn, Iceland."

Hvitarvatn is a glacier-dominated lake located on the eastern margin of Langjokull, Iceland's second largest ice cap. Hvitarvatn is ideally positioned to provide a continuous record of Holocene climate change as 1) glacial erosion and soft bedrock result in high lacustrine sedimentation rates, 2) diagnostic tephras of known age aid the geochronology, and 3) a relatively flat ice-cap profile responds sensitively to small climate-driven changes in the equilibrium line altitude (ELA). The erosive power of Langjokull and the efficient delivery system of these glacial sediments into Hvitarvatn are the dominant factors affecting both the nutrient and light availability in the lake. Any perturbations to the lake system, such as large fluctuations of the ice cap margin, result in a swift response in the diatom community due to the rapid growth and immigration rates of diatoms. The Holocene diatom assemblages preserved in Hvitarvatn sediments are a key proxy for recording Iceland's sensitivity to changes in North Atlantic circulation and addressing whether Iceland's large ice caps disappeared in the early Holocene, and if they did, when they re-grew. The presence of the Saksunarvatn tephra in the Hvitarvatn sediments indicates the lake was deglaciated by 10,300 yr BP. The Holocene Thermal Maximum (HTM) is represented in the lake sediments by an abundant, diverse benthic diatom population that dominated Hvitarvatn between 6000-9000 yr BP. A resurgence of ice cap activity around 6000 yr BP is reflected by a shift to a planktonic diatom assemblage composed mostly of Aulacoseira subarctica. Langjokull grew to its largest Holocene extent during the LIA and reached its maximum between 150-300 yr BP. Diatom assemblages during the LIA are largely composed of Aulacoseira islandica and Aulacoseira subarctica, reflecting extremely low light and turbid water conditions. The diatom assemblages in Hvitarvatn indicate very large environmental changes occurred during the Holocene in Iceland.

Nov. 30        Tiffany Duhl, INSTAAR
"The development of a low-cost, technologically modest method for determining urban fractional vegetation cover and type for use in urban air quality models."

The goal of this study has been to achieve an accurate urban fractional vegetation cover estimate for an approximately 7900 km2 study domain centered over the semiarid Maricopa County metropolitan area in Arizona, U.S.A. An additional objective has been to accomplish the above goal using low-cost and technologically modest tools, in order to make this process widely accessible to urban planners representing a diverse range of backgrounds and possessing varying levels of urban air quality modeling resources. Data and estimates of percent vegetation cover yielded by this study were incorporated into a landscape-level biogenic volatile organic compound (BVOC) emissions inventory used by the Maricopa Association of Governments (MAG) as part of an air-quality model for the Maricopa area. A modeling protocol requiring improved characterization of urban air quality for the Maricopa area was completed in 2006 after Maricopa County was designated as a nonattainment area for eight-hour ozone National Ambient Air Quality Standards set forth in the 1990 Clean Air Act Amendments. This talk will focus on the methods and preliminary results of this study, including the results of a quantitative validation effort undertaken to justify this technique.

Nov. 16      Brian Seok, INSTAAR
"Improving our understanding of trace gas transport mechanisms through the snowpack."

Members in the Atmospheric Research Laboratory (ARL) at INSTAAR have developed sampling techniques for continuous, vertical gradient measurements of trace gases in the snowpack. This research has been continuously expanding and currently focuses on studying gas exchange of O3, CO2, NOX and N2O with continuous, fully-automated and all winter-long experiments that are conducted at Niwot Ridge. Utilizing these techniques, we have shown large differences in ozone uptake to the snowpack in polar regions and sub-alpine regions. Similarly, fluxes of CO2, NOX and N2O appear to be much different in these environments. We are now studying what is causing these differences in snowpack-atmosphere gas fluxes and the mechanisms that control these gas exchange processes. Also, numerous trace gas flux studies in the snowpack assume simple diffusion and quantify gas diffusion processes using Fick’s law. Better understanding of the mechanisms and magnitudes of trace gas transport mechanism through the snowpack is necessary for more accurate assessment of C and N cycling over both polar regions and mid-latitude landscapes during the winter and for an assessment of feedbacks of climate change and snow cover change on global trace gas cycling.

Nov. 09      Rebecca Anderson , INSTAAR
"Rapidly melting ice caps of northern Baffin Island: insights from satellite imagery, cosmogenic and conventional radiocarbon dating"

The interior plateau of northern Baffin Island in the eastern Canadian Arctic is home to several small (50 km2) ice caps whose melt has been well recorded since 1949. Modern equilibrium line altitude (ELA) is well above all existing ice and a continuation of current climatic conditions will lead to the disappearance of all ice on the plateau in the future. Between 2000 and 2005, approximately 1 km2 of ice was lost per year, equivalent to ~1.3% of the total ice cover on the plateau. To put this current melt into a larger picture of ice-cap history on the plateau since deglaciation 6 ka, several techniques have been used in concert. The recent extent of the ice caps during the Little Ice Age can be estimated from the preservation of lichen trimlines across much of the plateau. These trimlines represent previous multi-year snow or ice cover and their aerial extent can be measured via satellite imagery. Based on these measurements, modern ice caps represent only ~3% of ice-cap extent during the Little Ice Age. Radiocarbon dating of moss, preserved beneath the ice caps due to their cold-based nature, suggests two periods of rapid, widespread ice cap growth at 650 calibrated years before present (cal BP) and 510 cal BP. Both periods coincide with volcanic events recorded in the GISP2 ice core, suggesting that cooling from increased aerosol loading may have triggered rapid ice-cap growth. Other earlier, and possibly more restricted, episodes of ice cap growth at ~1300 and 1000 cal BP also correlate with pulses of volcanic activity, furthering the link between volcanic eruptions and ice -cap growth. Further constraints on ice cap size are provided by 14C cosmogenic exposure dating. 14C concentrations in rocks at the modern ice margin are too low to be the result of continuous exposure since deglaciation followed by shielding for 500-1000 years by ice cover. Exposure history modeling indicates at least one additional prior period of ice cover of approximately 1000 years. This cold interval most likely occurred sometime since 4 ka, after the Holocene Thermal Maximum in the Arctic and coeval with the onset of Neoglaciation. Even without additional warming, continuation of current climatic conditions on northern Baffin Island will result in the demise of all ice on the plateau, a condition that has not occurred for more than 1300 years.

Nov. 02      Susan Riggins, INSTAAR
"Regolith development in alpine landscapes: Osborn Mountain, Wyoming and Niwot Ridge, Colorado"

Regolith consists of weathered rock and soil of any age that lies above fresh bedrock. Considered part of the critical zone, regolith is a product of weathering. It provides nutrients crucial to ecosystem functioning and moderates the impact of hazardous compounds at many spatial and temporal scales. The conversion of bedrock into regolith exerts control over rates of erosion and consequently over rates of evolution of landscapes.

While the rate of general regolith production has been documented in a variety of landscapes, the rates of the specific processes involved have not. Researchers have been working on regolith-related problems for nearly a century and yet few models on the origin of regolith development exist to explain its formation and aid in its understanding. While current models do provide empirical rates of regolith production, they fail to provide insight on the processes that produce regolith-a step needed to develop a non-empirical model. Current models treat their regolith term as a black box, with production values dependent only upon thickness of regolith.

Regolith production depends upon weakening of bedrock. Weakening can be accomplished through physical and chemical processes. These processes must work in concert. Taken individually, physical and chemical processes do not account for the entirety of regolith produced.

This project combines field work, laboratory analyses, and modeling to work towards developing a process-based model of regolith development. The individual pieces of this study will not exist in isolation. Each component will feed back into the other providing new information to incorporate into later field work and later iterations of the model.

Oct. 26      Florence Bocquet, INSTAAR
"Ozone exchange at the air-snow interface at the polar site of Summit, Greenland."

In recent decades, the Arctic has witnessed startling environmental changes prompting concerns about the Arctic climate system, which in turn, could amplify global climate change. We still remain remarkably ignorant of many aspects of how polar climate operates and its interaction with global environments. The boundary layer dynamics of ozone were studied at Summit, Greenland. Interactions between the atmosphere and the polar, year-round snowpack on glacial ice were investigated. Vertical profiles of ozone, as well as meteorological measurements, from a 12-m tower and within 1m deep in the snowpack, were obtained during March-August 2004. This field campaign provides continuous spring- and summer-time ozone exchange velocity [Ve(O3)] above a polar snowpack. Interestingly, the ozone exchange in the lower boundary layer is not a simple constant value as climate models assume, but is highly dependent on environmental conditions and on the snowpack chemistry. Meanwhile, the snowpack ozone concentration exhibits a distinctive diurnal gradient, stronger during the summer than the spring. While the dynamics of the snowpack ozone and the boundary layer ozone should be correlated, the mechanisms are not clearly identifiable. However, from these analyses, we propose hypotheses on the dynamical ozone chemistry that may likely occur at Summit, Greenland.

Oct. 19      Kaelin Cawley, INSTAAR
"Biogeochemical and ecological consequences of dissolved organic carbon released from soot particles from global firestorms at the Cretaceous/Tertiary boundary: Was the Strangelove Ocean a blackwater ocean?"

Phytoplankton productivity in the oceans was suppressed for about 10^4-10^5 years after the Cretaceous/Tertiary (K/T) boundary event, and many planktic marine species became extinct at the boundary. Proposed causes for what has been called the "Strangelove Ocean" include acidification of oceanic surface waters and effects associated with deposition from a global cloud of firestorm ash. We evaluate the potential effects on marine ecosystems of leaching of dissolved organic matter (DOM) from firestorm soot particles. Based upon the quantity of soot deposited in the boundary clay layer, we estimate that DOM concentrations in oceanic surface waters increased by at least a factor of two. This estimate is supported by an extrapolation based upon lacustrine DOM increases associated with deposition of ash in Rocky Mountain National Park from the Yellowstone fire of 1988. The leached DOM would have included soot-derived humic substances with chemical properties different from those of marine humic substances, such as a more aromatic character, greater absorptivity for visible light and greater quinone content. These humic substances could have acted as stress-inducing xenobiotic compounds and could have changed the physical and chemical characteristics of the marine environment. Cellular uptake of these humic compounds could have also inhibited calcite precipitation by coccolithophorids and foraminifera, contributing to the selective extinction of these species. The greater light absorption by the firestorm-derived humic substances could have caused surface warming and decreased the depth of the mixed zone, thereby limiting the subsequent dilution of DOM from the continents.

Oct. 12      Sean Bryan, INSTAAR
"Searching for Earth’s past climate in old mud: The process of deep sea sediment coring."

Much of what we know about Earth’s past climate comes from information found in deep sea sediment cores. This summer I had the opportunity to participate in a research cruise to the North Atlantic aboard the GO Sars. In this talk, I will present what I learned about shipboard life and the process of recovering deep ocean sediments.

Oct. 05      Tim Bartholomaus, INSTAAR
"Glacier sliding and subglacial water pressures: Kennicott Glacier’s response to the 2006 Hidden Creek Lake Jökulhlaup (A summer in the Wrangell Mountains, Alaska)."

The sliding of glaciers over their beds is a significant force in the landscape evolution of mountainous regions and is a major contributor to the observed, accelerated mass loss of many tidewater glaciers. However, this important piece of glacier dynamics remains poorly understood. At the Kennicott Glacier, Alaska, we availed ourselves of the drainage of Hidden Creek Lake beneath the glacier to observe how a considerable perturbation to the subglacial hydrologic system affects glacier sliding. As predicted, the glacier sped up significantly during last summer’s 5 July 2006 event, reaching surface speeds of up to 2.5 m/day, a daylong excursion from the summer average of 0.2 to 0.5 m/day. This speed up event was tightly synchronous with the filling of nearby ice marginal lakes we view as proxies for high water pressures within and beneath the glacier. On 28 June 2006, seven days prior to the Hidden Creek Lake jökulhlaup, or outburst flood, the glacier began a series of diurnal surges in horizontal speed and began to steadily lift from its typical bed-parallel motion, separating from the bed by a total of 30 cm before the jökulhlaup began. The onset of these changes in the motion of the Kennicott Glacier was coincident with a sudden 3°C increase in mean air temperature. When the flood occurred, the portion of the glacier down-valley of Hidden Creek Lake separated an additional 20 to 40 cm from its bed before collapsing back to the bed with a time scale of approximately 0.7 days. We hypothesize that the increase in air temperatures led to elevated meltwater generation on the glacier’s surface, which in turn increased subglacial water pressures. The sliding that occurred during the high water pressure immediately prior to the jökulhlaup allowed the poorly connected cavities beneath the glacier to link, creating an efficient conduit through which Hidden Creek Lake could drain.

Sep. 21      Ursula Rick and Maureen Berlin, INSTAAR
"How to Get Funding as a Graduate Student and Beyond."

Applying for graduate research funding can be a highly rewarding process. However, the success of a proposal depends on many factors, ranging from the details of the application form to the scientific merit of the proposed research. We present opportunities available to graduate students at INSTAAR, ranging from large federal fellowships to small research grants. Based on our experiences with applying for funding (with both positive and negative results!), we offer advice on how to construct a successful application. We also present strategies for obtaining post-graduate funding, based on new information from a recent NSF Antarctic New Investigators Workshop. Come armed with questions about your funding opportunities for an informative discussion.
     Presentation_PDF

Sep. 14     Jan Pollman, INSTAAR
"Evaluation and measurements of the global distribution of hydrocarbons."

In 1995, the Global Atmospheric Watch Program (GAW) of the World Meteorological Organization (WMO) proposed the establishment of a global monitoring program for light hydrocarbons in the atmosphere. Eleven years later, INSTAAR’s Atmospheric Research Lab (ARL) and NOAA have taken major steps towards this goal. We currently measure air samples collected twice a week at 40 different stations distributed all across the globe. Until today approximately 3000 samples have been analyzed in our lab. We expect that the interpretation of our results will result in a big improvement of our understanding of the atmosphere. Our understanding of the atmosphere is currently limited to certain species which gives reason for concern with regard to the current climate change. Our data will give insight into some of the currently less understood species present in the atmosphere. This work is currently in progress. In my presentation I will show the results from our measurements as well as first interpretations of the results. Highlight of this presentation will be the first plot to be ever displayed of the global distribution of butanes and pentanes. Previous measurements lacked the resolution needed on a regional and temporal scale.

Spring, 2006

May. 04        James Syvitski, INSTAAR Director
"How to be successful in Science."
     Topics will include:

• Paying the bills: hard money & soft money
• Asking the right question(s): staying relevant
• Advancing your science: work ethic & motivation
• Coping with fame and failure
• Working with colleagues
• Personal decisions: marriage, moves, career history

Apr. 27        Sean Bryan , INSTAAR
"Conversations with forams: interpreting past ocean conditions."
     Beyond the instrumental record of the past couple hundred years there is no direct way to measure ocean characteristics such as temperature or nutrient concentrations. In order obtain important information about the past state of the ocean, proxies must be developed. Much of what we know about the past ocean has been learned by studying the oxygen and carbon isotopes in the calcium carbonate shells of small zooplankton called Foraminifera. More recently, it has been found that the concentrations of trace elements (such as Mg, Cd and Zn) in foraminifer shells can contain information about the conditions of the seawater in which the organisms lived. However, biological processes involved in shell formation can alter the information that they are trying to tell us. In order to translate this information it is necessary to calibrate the proxies to modern conditions. This talk will give an overview of the different geochemical proxies and what they can tell us about the past. I will discuss the calibration process and the project that we are currently working on to calibrate these proxies in benthic foraminifera.

Apr. 20       Ken MacClune, INSTAAR
"The Atmospheric Methane Source: On the decline in the 21st century."
     Methane is the number two anthropogenic greenhouse gas and accounts for up to 21% of the enhanced greenhouse effect. Since the start of the industrial revolution and until recently the concentration of methane increased at a pace that tracked the growth in human population. This is due to many human activities such as rice and livestock agriculture, and fossil fuels extraction contributing to the methane concentration. But since the early 1980s the growth in methane concentration has slowed despite a continued increase in the human activities.
      Using an improved version of a 1-box model of the atmosphere published by Lassey et al in 2000 I have been able to extend their record of atmospheric methane concentration and carbon isotope change to show that in the last eight years the methane source has started to decline. Is this decline a permanent feature or an anomaly? In order to answer that question more knowledge is needed of what the source or sources are that are behind this change. I will discuss plans to expand the models temporal, spatial, and species resolution in the hopes of revealing the source(s).

Apr. 13        Cynthia Cacy, INSTAAR
"Chemical weathering in loess soils of the Matanuska Valley, Alaska."
     On geologic timescales, atmospheric carbon dioxide levels are controlled by the balance between volcanic out-gassing and consumption of CO2 through silicate chemical weathering. However, the relationship between increased weathering associated with uplift, physical erosion, and climate remains uncertain. Uplift may incite mountain glaciation, which raises the question what is the relationship between glacial activity and silicate weathering rates?
      We hypothesize that in periglacial areas glacial loess-derived soils enhance chemical weathering fluxes in three ways. First, small grain size of loess increases the surface area for weathering reactions. Second, ongoing loess deposition supplies fresh mineral material for weathering. Last, loess is deposited in vegetated areas, and this vegetation provides organic acids that promote silicate weathering. We tested hypothesis by calculating chemical weathering fluxes using a mass-balance approach along a 50 km transect of loess-derived soils in the Matanuska valley of south-central Alaska. Loess deposited during the last 6500 years of the Holocene is >20 meters deep close to river sources but depth declines exponentially downwind. Estimates of particle surface areas reveal that loess soils contain about twice the surface area of till-derived soils of the same thickness hence increasing the potential for chemical weathering.
      Along our transect, podzolic soils appear where loess thickness falls below 1 m corresponding to loess rain of about 0.15 mm/yr. This suggests that organic acids are buffered by weathering loess where deposition rates are greater than 0.15 mm/yr. Mass-balance analyses along the transect show that weathering fluxes increase with lower deposition rates, finer grain size, and lower pH. This study has two interesting implications. First, ice-age loess rain may have been responsible for maintaining high levels of soil fertility in soils distant from ice sheet margins. Second, the soils whose chemical weathering was the most influential in drawing down atmospheric CO2 during past ice ages may have been those located relatively far from ice margins.

Apr. 06       Trevor Popp , INSTAAR
"An Ice Chorus: Paleoclimate Results from Greenland and Antarctica Ice Cores and a Look to the Future."
     I will present an overview of my seven years in ice core science that has endeavored to characterize and understand the anatomy, speed, and timing of climate change with high-resolution ice isotope time series data from ice cores from NorthGRIP and GISP2 in Greenland and Mt. Moulton in West Antarctica.
      Greenland ice cores are uniquely suited for study of abrupt climate events because relatively high snow accumulation rates allow single years to be identified well into the last glacial period. Detailed temporal and spatial examination of past abrupt climate changes recorded in Greenland ice is now possible due to the availability of several deep Greenland ice cores coupled with the routine measurement of annually or better resolved proxy data. I will present ice stable isotope measurements (oxygen-18 and deuterium) across the entire last deglacial transition and several other Dansgaard-Oeschger events in the NorthGRIP ice core with near-annual resolution, as well as several of these same climate transitions in GISP2 ice with similar detail.
      Meanwhile, precise absolute determination of the timing of deglacial transitions is crucial for determining the fundamental causes of climate change and the origin of the 100,000 year glacial-interglacial cycle and to test the Milankovitch Theory. The summit of Mt. Moulton, West Antarctica contains a horizontally-exposed section of stratigraphically ordered blue ice with more than 40 intercalated volcanic ash layers (tephra) from the nearby volcano Mt. Berlin. A subset of these layers are datable using the 40Ar/39Ar technique which are now being used to develop an independent and absolute age model for records developed from the surrounding ice and trapped gases. Thus, the Mt. Moulton records are the first in ice to combine continuous proxy data with an independent radioisotopically derived time scale. The most important result so far is a date constraining onset of the last interglacial in West Antarctic at or just after 135.8 ± 1.1 kyr BP.
      I will conclude with a preview of what is to come in the next decade from the international ice core communities.

Mar. 09      Zach Guido , INSTAAR
"LGM glacier retreat rates and the timing of terrace formation in the Animas River drainage, San Juan Mountains, Colorado."
     The San Juan Mountains in southwestern Colorado lack constraints on the timing of the Last Glacial Maximum (LGM) and river terrace formation. Only three absolute ages exist in the entire San Juan Mountain Range. We augment these age constraints with cosmogenic 10Be ages on two terraces and 9 glacial polish samples in the Animas river valley. We report ages that provide the first quantification of the Animas valley glacier's LGM retreat history. In addition, the conceptual models that (1) suggest rivers respond to the sediment input delivered by glaciers and (2) support the claim that paleo-glaciers record the rate and magnitude of climate change will be tested.

Mar. 02      Craig Lee, INSTAAR
"Ice Patch Archeology: The global phenomena and the need for focused surveys in the Rocky Mountain West."
     In recent decades, paleontological and archeological remains have been discovered in association with perennial snow and ice patches and glaciers in much of western North America, including Alaska and Washington in the United Sates and the Yukon Territory and British Columbia in Canada. This presentation discusses how these finds are reshaping our perception of alpine paleoecology and human prehistory, and provides exciting details about current and pending research in the Colorado Front Range and Beartooth Plateau of Montana. In particular, the talk will focus on the ongoing paleontological analysis of two bison skulls discovered in association with a melting ice patch in Rocky Mountain National Park (RMNP). The discovery of fragile organic materials, such as the c. 600 and 1000 year-old skulls form RMNP, in association with perennial snow and ice features suggests their associated environments are experiencing atypical melting. Because such rare and irreplaceable specimens and artifacts rapidly deteriorate when exposed to the elements, there is an urgent, regional need for focused surveys in the Rocky Mountain West, similar to those conducted in Alaska (Dixon et al., 2005) and the Yukon Territory (Hare et al., 2004). Locations like RMNP, where diminishing snow and ice resources exist, may contain additional uncommon and informative materials like those discovered elsewhere in the Colorado Front Range (Lee et al. 2006). Although no definitive association between the paleontological specimens and native peoples has been demonstrated in the Colorado Front Range, research is in its early stages and ice patches here may yet be found to contain evidence of prehistoric human activity.

Feb. 23      John Behrendt , INSTAAR
"Innocents on the Ice: A young grad student's oversnow traverses in Antarctica During the IGY Era."
     When 12 countries established scientific stations in Antarctica for the 1957-58 International Geophysical Year (IGY), the Cold War was at its height, seven countries had made claims in Antarctica, and the Antarctic Treaty was a few years in the future. The U.S. program was operated by the Navy and territorial claims were secretly made at several locations during the IGY; these were never officially announced and the U.S. remains a non-claimant state. I was a graduate student geophysicist (assistant seismologist) on the unexplored Filchner-Ronne Ice Shelf as part of the only major field project of the U.S. Antarctic program.
     Starting in 1957, the U.S. began a series of oversnow traverses making seismic reflection ice soundings (and other geophysical measurements) and glaciological studies to determine the thickness and budget of the Antarctic Ice Sheet. The U.S.S.R. and France made similar traverses coordinated through the IGY. Although geology and topographic mapping were not part of the IGY program because of the claims issue and the possibility of mineral resources, the oversnow traverse parties did geologic work, where unknown mountains were discovered. The oversnow traverses continued through 1966 and resulted in an excellent first approximation of the snow surface elevation, ice thickness and bed topography of Antarctica, as well as the mean annual temperature of that era and snow accumulation.
     The vacuum tube dictated the logistics of the oversnow traverse program. Seismic equipment including heavy batteries weighed about 500 kg. Therefore a Sno-Cat tracked vehicle was needed to carry this load. Usually three such vehicles were needed for safety. Because about 3 l/km of fuel were consumed by each Sno-Cat, about 100 kg/day of fuel per vehicle was required. A resupply flight could carry only ~600 kg/flight (varying greatly as to range and type of aircraft). Other than the resupply of the seven U.S. stations in Antarctica, the major air logistic effort of the U.S. IGY program was support of the three oversnow traverses.
     The Filchner Ice (Shelf) Traverse, 1957-58, in which I participated, encountered many crevasses. Vehicles broke through thin snow bridges and one man fell deep into a crevasse. Fortunately there were no deaths and only one serious injury resulting from crevasse accidents on the U.S. oversnow traverse program, in contrast to an aircraft death rate of 3.8 deaths per year in the U.S. program from 1955-61. In contrast, since the 1970s the US program has a death rate of about 0.1 fatalities/year in Antarctica.
     The oversnow traverses of the IGY employed the inductive method of scientific research with only the general objectives of defining the Antarctic Ice Sheet as to surface elevation, thickness, snow accumulation and temperature. In contrast, Antarctic research today employs deductive logic with narrowly defined objectives and testing of hypotheses. This change has been necessary because of expense, and competition of proposals by many scientists. Nonetheless something has been lost by this approach, and there is still the need for "exploration" types of research is the still unknown vast continent of Antarctica.

Feb. 16      Colleen Flanagan, INSTAAR
"Climate variability and phytoplankton community composition in an alpine lake, Colorado."
     Because the hydrologic regime of alpine catchments is dominated by snow melt, these aquatic ecosystems are sensitive to fluctuations in the amount of snow, chemical nature of snow, and timing of snowmelt. Investigations of two alpine step lakes, Green Lakes 4 and 5, located in Niwot Ridge Long Term Ecological Research (LTER) site in the Front Range of Colorado, have shown that earlier, warmer springs, longer growing seasons, thinner ice cover, and increased atmospheric nitrogen deposition have occurred over the past 20 years. We examined how these climate processes drive the variability of the phytoplankton population. Climate records from 1981 to present were analyzed, algal biomass was quantified from GL4 and GL5, and samples for community composition were analyzed at GL4 throughout the summers of 2000 2004. For example, a principal components analysis confirmed taxon-specific shifts in the community composition during the drought of 2002 in Colorado. Further, the peak in algal biomass coincides with the ice-out date and subsequent higher water temperatures, lower discharge and higher hydraulic residence time. Although based on only six seasons of monitoring data, these results may foreshadow climate change and implicate subsequent biological effects in high altitude watersheds.

Feb. 09      Rebecca Anderson, INSTAAR
"Ice cap retreat in northern Baffin Island: providing a context for current Arctic warming."
      Evidence of current warming of the Earths climate can be found from widespread regions around the globe. However, the magnitude of this warming varies geographically. Nowhere is warming felt more strongly than in the Arctic, where average temperatures have increased between 2-4ºC since 1970, due to positive feedbacks such as earlier snow melt and reduced sea ice extent. One of the biggest questions posed to climate scientists today is: is this warming within the realm of natural variability or is its rate and magnitude beyond that which can be explained by natural phenomena? The aim of this project is to provide a Holocene context for 20th century Arctic warming. How unusual is the magnitude of this warming? When was the Arctic last as warm as it is now? Is this degree of warmth within the range of natural variability or is it unprecedented? The rapid melting of ice caps within the interior of Baffin Island, arctic Canada, has been documented over the last 50 years by aerial photography, satellite imagery and ground observations. These ice caps have diminished by 97% in area from their maximum extent during the Little Ice Age; many have already melted away completely, while others are projected to disappear in the near future, based on their current retreat rates. 14C-dating of moss preserved beneath the ice indicates that the last time certain parts of the plateau were ice-free was just over 1000 years ago and therefore, this area has not experience warming comparable to that of today for the last 1000 years. Two other techniques that will extend the record of these ice caps through the entire Holocene are cosmogenic isotope dating of rocks adjacent to the ice caps and lake core analysis from lakes recently exposed by the receding ice margins. Used together, these three techniques can provide a picture of ice cap extent throughout the Holocene and help to place their current retreat in a larger time frame.

Feb. 02     Jessica Black , INSTAAR
"Diatoms as proxies for a fluctuation Holocene Ice Cap margin in Hvítárvatn, Iceland."
     There are no complete records of terrestrial environmental change for the Holocene (11,000yrs) in Iceland and the status of Icelandic glaciers in the early Holocene remains unclear. It is not even known whether Iceland's large ice caps disappeared in the early Holocene, and if they did, when they re-grew. Icelandic lakes are particularly well suited to address these uncertainties as: 1) Glacial erosion and soft bedrock result in high lacustrine sedimentation rates, 2) Diagnostic tephras aid the geochronology, 3) Iceland's sensitivity to changes in North Atlantic circulation should produce clear signals in key environmental proxies (diatoms) preserved in lacustrine sequences, and 4) Ice-cap profiles are relatively flat so small changes in the equilibrium line altitude result in large changes in accumulation area. Hence, large changes in ice-sheet margins during the Holocene will impact sedimentation in glacier-dominated lakes and the diatom assemblages at those times.
      Hvítárvatn is a glacier dominated lake located on the eastern margin of Langjökull Ice Cap in central-western Iceland. Approximately 132m of sediment was recovered from four locations in Hvítárvatn during the GLAD4 drilling project, July 2003. The uppermost Hvítárvatn sediments, which include the Little Ice Age (LIA), are characterized by thick varves (~1cm thick) and multiple large pulses of ice rafted debris (IRD) originating from two outlet glaciers in contact with the lake. The most recent ~ 800 years of sediment deposition reflects a glacially dominated system that is dominated by planktonic, silica-demanding diatom taxa. These taxa suggest a high dissolved silica and turbid water environment consistent with high fluxes of glacial flour. Below the LIA are Neoglacial sediments deposited when Langjökull was active, but outlet glaciers were not in contact with Hvítárvatn. The Neoglacial sediments are varved, but contain only a few small IRD pulses. The Neoglacial diatom assemblage is also dominated by planktic, silica-demanding taxa and shows a small increase in diatom abundance. A distinct shift in lake conditions is reflected in the massive, organic rich sequence below the Neoglacial sediments. The abundance of diatoms is an order of magnitude greater than elsewhere in the core and the diatom assemblage is predominantly benthic. These diatoms were deposited in clear water conditions likely found in an environment with warmer summers than present and with no glacial erosion. Langjökull must have disappeared in the early Holocene for such a diverse, benthic dominated diatom assemblage to flourish. These sediments were deposited between ~7800 to ~5600 AD and represent the Holocene Thermal Maximum (HTM) in Iceland.

Jan. 19      Henry Adams and Jeff Lukas , INSTAAR
"Boring trees, interesting science: adventures in dendrochronology in the semi-arid West."
   Throughout the semiarid regions and elevations of the western U.S., the radial growth of trees is influenced primarily by moisture availability during the year prior to and including the growing season. Because the pattern of wide and narrow rings, driven by the common climate signal, is highly replicated within sites, individual trees even dead ones can be absolutely aged, or crossdated. And the crossdated ring widths can then serve as a multi-century proxy for moisture variability and its associated metrics, such as annual precipitation and streamflow. Finally, the proxy records of climate can be used to investigate the influence of climate variability on the temporal patterns of tree establishment and mortality discerned via crossdating.
    We will present four recent and ongoing projects in Colorado, Utah, and Arizona, addressing very different research questions, which have in common the use of these dendrochronological methods. In brief, the four projects are: extending millennial-length records of drought variability with long-dead wood; reconstructing the history of a cottonwood bottomland forest; investigating the drought response of different species at different elevations on one mountain; and determining the influence of land use and climate on the structure of pinyon-juniper woodlands.

Fall, 2005

Nov. 17       Dylan Ward, INSTAAR
"The use of cosmogenic radionuclides in stratigraphy: Application to the Nenana Gravel, Alaska Range."
     We use a modification of the cosmogenic radionuclide (CRN) burial dating technique (differential decay of 26Al and 10Be) to constrain the age range and deposition history of the Mio-Pliocene Nenana Fm. gravel in the central Alaska Range, AK. The Nenana Fm. consists of coarse fluvial gravel and debris flow deposits sourced in the newly emergent Alaska Range. Deposits of the Nenana Gravel up to ~1200 m thick record the exhumation of specific Alaska Range lithologies beginning south of the Denali Fault and progressing northward. The period of deposition of the formation is bracketed by an underlying tephra dated using 39Ar/40Ar to 6.7 Ma and the emplacement of 2.79 Ma Jumbo Dome into the Nenana Gravel. That the latter relation indicates an end of deposition by this time is disputed, however, and no direct dating has been performed on the gravel itself. Standard CRN burial dating is inapplicable to the Nenana Gravel because the requirement for instantaneous burial is not satisfied. The bracketing ages for the formation imply a mean deposition rate of 0.3 mm/yr, which, while rapid, does not instantaneously cut off buried sediment from the zone of CRN production (~35 ka are spent within 10 m of the surface). We thus modify this method to accommodate the effects of CRN production and decay during progressive burial of sediments. Burial rates are derived by using a 1D numerical model to fit a depth profile of 26Al, 10Be, and their ratio to measured isotope concentrations, assuming incoming sediment is initially buried with a cosmogenic production ratio of Al/Be between 6.0 and 6.1. Absolute ages can be calculated once burial rates are constrained. Importantly, this method allows us to date very old sediments in this setting, as the extra time spent by the sediment in the CRN production zone increases its overall CRN concentrations above the values inherited from exhumation and transport. Eight sand and quartz-rich pebble samples were collected in exposures along Suntrana and Alaska Creeks, which allowed access to ~1200 m of section of the Nenana Gravel. We also collected three samples from a 30 m section of Nenana Gravel equivalent exposed at Honolulu Creek south of the Alaska Range. Two samples of modern Nenana R. sediment were collected to constrain initial inherited values of the Al/Be ratio in the modern setting. Samples were processed at the University of Colorado Cosmogenic Isotope Lab for analysis at the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Laboratory. This suite of samples should allow reconstruction of deposition rate history within the Nenana Gravel, helping to constrain the early history of exhumation in the core of the Alaska Range.

Nov. 10       Jan Pollmannn, INSTAAR
"The Tale of Atmospheric Hydrocarbons: What do we know, what do we not know and why do we care?"
     Atmospheric hydrocarbons and especially non-methane hydrocarbons play an important role in the troposphere. Whereas the vast majority of the atmosphere (> 99%) consists of non-reactive gases, these particular compounds are highly reactive. In this presentation I will explain how researchers can use exact measurements of these compounds to understand atmospheric processes, such as chemical reactions or transport. The sources of NMHC are mostly combustion processes, such as fossil fuel burning or biomass burning. Different combustion processes yield different kind of NMHC emissions giving researchers the opportunity to identify the recent history of an air mass.
     These compounds can also be used to determine the age of an air mass due to their vastly different atmospheric lifetimes. I will explain how the variability in a long data series can be used to find out useful information about a particular sampling site and about the atmospheric composition.
     Lastly, recent measurements of hydrocarbons from the NOAA flask sampling network will be presented. Application of this data along the above mentioned lines will be briefly discussed.

Nov. 03      Shad O'Neel, INSTAAR
"Complete carnage at Columbia Glacier: Iceberg calving and fast flow......What are we learning?"
     Over the past year we performed an extensive field campaign at Columbia Glacier Alaska, in order to better understand the rapid retreat that has been occurring since ~1980. The talk will highlight the changes at the glacier, including changes in geometry and speed, and will discuss the ups and downs of the field program as well as introduce some of the new data sets that are being assembled.

Oct. 27      Aurelie Justwan, Norsk Polarinstitutt
"Variability of the Irminger Current during the Holocene."
      A high resolution sediment core, taken during the IMAGES cruise in 1999, MD99-2269 from the northern shelf of Iceland has been studied to assess the stability of the East Greenland Irminger current system during the Holocene. The core has a 20m long Holocene section, which was studied at a decadal scale. The chronology of this section is established by 24 AMS dates and the Saksunarvatn tephra layer. Diatoms are utilized to reconstruct Sea Surface Temperature (SST). Three different transfer function methods have been used to reconstruct the SST at this site: WA-PLS, Maximum Likelihood and Imbrie and Kipp. The combined use of the three methods allows the SST reconstruction with a higher confidence level. Those three reconstructions generate very similar SST trend through the Holocene. The onset of the Holocene is characterized at the site by a steep temperature increase at 10 kyrs of almost 4°C. The Holocene climate optimum is recorded between 7 and 4.5 ka. The SST is around 2°C warmer during the major part of the Holocene compared to the SST for the last 1000 years. The cooling of the SST might be the result of a southward movement of the East Greenland-Irminger current system. The record at this site is compared to two other records, one south of the present site, LO 09-14, on the eastern branch of the North Atlantic Current, allowing a North south transect through the area. The second core MD95-2011 is located on the western branch of the North Atlantic Current and allowed the study of a east west transect through the area. The Holocene climate optimum occurs simultaneously at the studied site and at the LO09-14 site, further south. However, the Holocene climate optimum at the MD95-2011 site occurs earlier, suggesting a change in the strength of the western and eastern North Atlantic Current.

Oct. 20      Ursula Rick, INSTAAR
"Meltwater Movement on the Greenland Ice Sheet."
     One uncertainty in ice sheet mass balance is the destination of surface meltwater. The runoff limit is the elevation above which surface melt percolates into the underlying cold snow and refreezes, thus the local mass balance above this elevation remains unchanged due to melt. Below the runoff elevation, the annual quantity of melt is great enough to supply the heat required to raise the snow temperature to the melting point and to satisfy the residual water content requirement of the firn, leaving enough meltwater to travel downslope and out of the glacier system. Passive microwave data from the Scanning Multi-channel Microwave Radiometer (SMMR) and Special Sensor Microwave Imager (SSM/I) have shown that melt is occurring at higher elevations (further inland) on the Greenland Ice Sheet, which may lead to an increase in the elevation of the runoff limit. It is unknown how many years of melt are required to move the location of the runoff limit to a higher elevation. A theoretical model shows this time to be much less than the time required to completely fill the underlying firn pore space with superimposed ice (~102 years). Increased meltwater flow into the underlying firn will also alter the stratigraphy. Subsurface flow in the firn occurs heterogeneously and forms horizontal ice layers and vertical ice pipes on refreezing. These structures (especially ice layers) may have a strong influence on subsequent water flow in the firn and facilitate downslope transport of water along perched horizons, leading to greater runoff of melt.

Oct. 06      Maureen Mason, INSTAAR
"Knickpoint migration on the Roan Plateau, Colorado."
     The Roan Plateau, located in western Colorado, is a complex landscape of cliffs, waterfalls, and rolling hilltops, all carved into essentially uniform, flat-laying sedimentary bedrock. This landscape is responding to downcutting of the upper Colorado River, which began sometime in the late Cenozoic, and led to a wave of incision into the southern edge of the Roan Plateau. A cursory observation of a topographic map of the Plateau reveals approximately 30 knickpoints (over-steepened reaches in longitudinal profiles) in tributary streams (Parachute Creek and Roan Creek). These knickpoints record the response of the Plateaus bedrock streams to changes in the Colorado River base level, and provide a natural experiment in bedrock river incision.
     This presentation discusses the results of a simple stream power model to predict the locations of knickpoints on the Roan Plateau. The model specifies that knickpoint migration rates are proportional to contributing drainage area (as a proxy for stream discharge) above a threshold, and to rock susceptibility to erosion. Model parameters are constrained by specifying an arbitrary time to initiate knickpoint propagation, and then assessing rock susceptibility and threshold power parameters which best predict the knickpoint location on a single tributary stream. Models of the Parachute drainage (11 knickpoints) show the expected rapid initial propagation, which declines as tributary junctions are passed. The present locations of knickpoints can be reasonably predicted (within 1 km) with a single rock susceptibility and with minimal erosional threshold. Tradeoff between rock susceptibility and timing of Colorado River incision makes the susceptibility constant ambiguous. I will discuss attempts to use the cosmogenic burial method to date a Colorado River terrace gravel deposit 200 meters above the Colorado River on Battlement Mesa, just south of the Plateau, as a way to constrain independently the timing of initiation of incision. Future work on knickpoint processes and hilltop landscape evolution
are also discussed.

Sep. 29      Lana Cohen, INSTAAR
"Science at the Summit: Year-round investigations at the Greenland Environmental Observatory (GEOSummit)."
      Summit Camp, atop the Greenland ice sheet, is the site of a great deal of important scientific research. This research station on the largest ice sheet in the Northern Hemisphere supports year-round investigations into atmospheric and snowpack processes. While initial investigations at this site primarily focused on atmosphere-to-firn dynamics to aid in interpretation of ice core records, it has since been discovered that the Arctic troposphere exerts significant influence on the global atmosphere through its role as an atmospheric chemical reactor. In addition, the ice sheet itself is important for atmospheric chemistry, since snow is not an inert surface, but instead provides surfaces for active heterogeneous chemistry, and acts as a major source and sink of several important atmospheric compounds. Recently, the site’s remoteness from direct anthropogenic influences has also made it valuable as part of a global monitoring network for greenhouse gases, halocarbons, ozone, and aerosols.
     This presentation summarizes the major year-round investigations currently happening at the Greenland Environmental Observatory at Summit (GEOSummit) and discusses some of the findings of these studies, including discovery of the Arctic ozone hole, the origin of tropospheric ozone at Summit, the surprisingly active photochemistry of the snowpack, and the validity of comparisons between Summit and other polar sites such as South Pole, Antarctica.

Sep. 22      Craig Anderson, INSTAAR
"Modeling spatially distributed snowpack properties to enhance our understanding of snow-elk relationships in the Northern Elk Winter Range, Yellowstone National Park."
     The Northern Elk Winter Range (NEWR) in the Greater Yellowstone Ecosystem (GYE) is an exemplar for globally significant biological resources. Key resources and processes range over a complex, human-perturbed ecosystem that is partitioned among a variety of decision makers. Rocky Mountain elk are an important biotic component of the NEWR and are the most abundant ungulate species on the range. At the same time, elk are an important resource for human related activities such as hunting, wildlife viewing, and tourism in general. As a result, elk can serve as a common currency for investigating complex interactions between biophysical and human systems. In order to evaluate the complexity of biophysical-human system relationships using elk as indicators, it is necessary to first gain a better understanding of the environmental factors that impact elk energetic expenditures and distributional responses.
     Winter severity is the primary control on elk populations in the NEWR of Yellowstone National Park (YNP). Recent advancements in radio tagging and GPS technology have improved the ability of researchers to obtain more detailed positional data on elk movement during the winter. These improvements in data collection technology have necessitated a move towards understanding snow properties at finer temporal and spatial scales than currently exist. Here, we evaluate the development of a spatially-distributed snow model based on parsimonious data requirements to improve our understanding of snow-elk interactions in the NEWR. We spatially distributed the 1-D SNTHERM point model for two basins in the NEWR by classifying the study area into 30 discrete regions using a combination of elevation, aspect and landcover type, with elevation having the largest effect on snow depth (R2 = 0.45). Modeled versus measured comparisons show that modeled estimates of snow depth, density, and snow water equivalent were highly correlated with measurements from monthly snow pits in each landscape type, with R2 values ranging from 0.91-0.94. Extending the model to areas outside of the test basins also provided significant correlations between modeled and measured snowpack properties, with R2 values ranging from 0.67 to 0.71. Modeled daily SWE values were also highly correlated with measured daily SWE values at several SNOTEL sites surrounding the NEWR. These relationships were used to retroactively estimate the spatial distribution of snow properties over the NEWR domain from historical records of point measurements at SNOTEL sites. Comparisons of estimated and measured 2003 SWE values showed strong correlations at 23 landscape types, with R2 values ranging from 0.51 to 0.67. This research highlights the importance of continuing efforts to improve methods for modeling the spatial and temporal distribution of snowpack properties given the substantial impact these properties appear to have on the survival and overall winter ecology of elk in the NEWR.

Sep. 15      Paul Abood , INSTAAR
"A deposition discussion: Issues surrounding atmospheric inorganic N deposition measurement."
      Atmospheric nitrogen deposition is a subject of continued research interest because of its effects on sensitive ecosystems. Ammonium (NH4+) and nitrate (NO3-) deposition stimulates organism growth in nitrogen-limited environments; such growth potentially alters the structure and diversity of native communities. NO3- contributes to soil and water acidity in sensitive environments.
     Dry atmospheric deposition measurement gains much attention because of the much greater costs and analytical uncertainty involved as compared to wet deposition. An outstanding question at many locations is the contribution of "dry" deposition to total annual chemical deposition. This research evaluates the role of dry deposition in total deposition at Park Research and Intensive Monitoring of Ecosystems Network (PRIMENet) sites during the period 1998-2003. The analysis includes reporting on the percent contribution of dry deposition to total deposition and year to year variations in the ratio of wet to dry deposition at each site, and an evaluation of whether the results support converting wet deposition values to total deposition by using a simple wet:dry ratio based on the PRIMENet data.
     Wet deposition measurements are generally a less contentious subject. The National Atmospheric Deposition Program (NADP) isopleth maps are used to characterize the "chemical climate" and observe its changes over time. Government agencies use the isopleth maps to inform policy decision; scientists use the maps to understand deposition fluxes to evaluate changes in the chemical climate. However, NADP sites located in mountain environments are generally not represented in the isopleth maps because they do not meet the NADP completeness criteria for most annual periods. The reason for this failure is that as much as 80% of annual precipitation falls as snow. Rain gages and chemistry collectors have very different catch efficiencies for snowfall, which leads to the failure to meet completeness criteria 4. This research shows that national isopleth maps for inorganic nitrogen and for precipitation amount would be substantially changed for the central Rocky Mountains and for the Sierra Nevada if these mountain sites were included in the national isopleth maps. NADP may need to change their completeness criteria so that these snowfall dominated sites can be included on the national isopleth maps.

Sep. 08      Tiffany Duhl, INSTAAR
"Uptake and emission of biogenic volitile organic compounds by plants."
      Vegetation emits a vast array and substantial quantities of biogenic volatile organic compounds (BVOC), which play a major role in air quality, secondary aerosol formation (SAF), carbon sequestration and biosphere-atmosphere interactions. Early BVOC studies focused on isoprene, while more recent research has also included numerous non-isoprene BVOC, and indicates that BVOC fluxes recycle a considerable amount of sequestered carbon to the atmosphere.
     Aside from their atmospheric implications, many classes of BVOC (especially terpenoids) have been discovered to be mediators of plant-insect and plant- plant interactions. There are still many questions surrounding the quantity of BVOC emitted by vegetation and the role these compounds play in atmospheric and biospheric interactions. Many species of BVOC are implicated in attracting pollinators, and are likely involved in indirect defenses against insect herbivory. Aside from these functions, some BVOC species may also be involved in allelopathic activity, protection against thermal damage, and other roles.
      An area of research that has received less attention, however, is the uptake of BVOC by plants. Very little knowledge exists about which compounds are taken up by vegetation, what the uptake rates are and on the physiological role of BVOCs in plant-plant interactions. In this research symposium, I will provide an overview of BVOC from an atmospheric as well as a biospheric perspective. I will then present my own research goals regarding BVOC emissions and uptake, as well as progress I have made to date, including methods, challenges, and preliminary results.

Sep. 01      Rhea Esposito & Shannon Horn, INSTAAR
"Community assemblage and endemism in Dry Valley stream diatoms: Two facets of diatom response to climate change."
      This study examines long-term patterns between stream diatom assemblages and climate conditions in the McMurdo Dry Valleys, Antarctica and, ultimately, the effect of nutrient conditions and flow regimes on these communities. Our goal is to gain information about the climate of Antarctica throughout its history. It has been shown that stream flow is influential on assemblage composition, illustrated by a negative linear relationship between relative endemic abundance and stream flow. Stream flow is related to solar radiation and other environmental conditions affected by climate change. We found that diversity and endemism have a curvilinear quadratic relationship (highest diversity at intermediate levels of endemism) for freshwater diatoms in glacial melt water streams of the Dry Valleys. During low flow events, as endemism increases, diversity drops. We found higher assemblage diversity and higher percentages of endemic species for diatoms in these streams than previously reported for the Antarctic continent. Counter to expectations for extreme environments, our data show that co-occurrence of endemic species with widespread species promotes diversity in diatom assemblages, and low flow raises endemism and lowers diversity.

Spring, 2005

Apr. 07       Tara Chesley, INSTAAR
"Mineralogy, sediment, and foraminiferal history of Djúpáll, Iceland: Reconstructing a past record."
     I will discuss the sedimentology, mineralogy, and foraminiferal assemblages from core B997-338 from Djúpáll, NW Iceland to help better understand the climatic history of this site. New 14C dates require a revision of the chronology presented in earlier papers. It is hypothesized that this core has undergone periods of reworking which provided the confusion for the chronology. Core B997-338 consists of four lithofacies of which the lowermost is a diamicton (till?) with high carbonate content. Two programs, RockJock and MinUnMix have been used to quantify the <2mm sediment mineralogy. RockJock is the Quantitative Phase Analysis (QPA) of XRD scans. The samples are spiked with ZnO, ground to a powder, and scanned between 5° and 65° two theta. MinUnMix takes the RockJock results from two end members and a sample needing to be “un-mixed”. The program is able to statistically determine what percentage of the sample is from which end member. The non-clay mineralogy consists mostly of feldspars (labradorite and bytownite) and pyroxene (diopside), while the clay fraction consists of smectite. Quartz, which can be used as a tracer for non Icelandic sediment, is in very low abundance from 0-0.7%. In addition counts of the 150-1000 µm sand fraction were carried out to also determine the mineralogy. Foraminiferal assemblages were picked and analyzed to test the hypothesis of reworking. Two different assemblages were analyzed from each depth. One consisting of the “well preserved” specimens and the other consisting of the “poorly preserved” foraminifera. These assemblages were also submitted for isotope data. These data do support the reworking hypothesis.

Mar. 31       Rose Cory and Chris Jaros, INSTAAR
"Pony Lake, Cape Royds, Ross Island, Antarctica: Interested in a chance-of-a-lifetime time-share opportunity?"
     Experience firsthand the excitement of biophotogeochemical characteristics of Dissolved Organic Matter in Antarctic waters. Experience the "Heroic Age" of British Polar exploration from the catered comfort of your own heated helicopter/Skidoo/Hagglund. Marvel at the "aroma" of hundreds, if not thousands, of years of penguin quano accumulation. Former owner a true handy-man and visionary, plus the adapted Outback-Colonial Architecture makes this lakeside cabin a must-see! "Men wanted for hazardous journey." Just kidding, the only hazard will be falling off the front of your chair!

Mar. 17      Annalisa Schilla, INSTAAR
"Climate Insights from the Siple Dome Ice Core."
     I will present the stable isotope (delta 18O) and deuterium excess (d) records from the Siple Dome ice core, which was recovered from the climatically sensitive West Antarctic ice sheet (WAIS). The stable isotopes are proxies for the temperature at the ice core site, and the deuterium excess is a proxy for conditions at the moisture source. The Siple Dome site receives moisture from the Pacific Ocean and is currently strongly influenced by modern Pacific climate (e.g., El Nino-Southern Oscillation). WAIS is a marine-based ice sheet which has disintegrated in past warm periods and is potentially unstable in a greenhouse-warming world. The Siple Dome ice core is also high enough resolution to be cross-dated precisely relative to Greenland ice cores, lending insight into the global synchroneity of climate changes. The Siple Dome site provides clues to the history of WAIS and global climate that are therefore fundamental to our ability to predict future climate changes.

Mar. 10      Florence Bocquet , INSTAAR
"Air-snow Interactions: Summit, Greenland and Niwot Ridge, Colorado. Two different places in the world, two different stories."
     During two campaigns, one in July 2003 and the other from March to August 2004, ozone mixing ratio measurements above and within the permanent polar snowpack of Summit, Greenland were performed. Ozone mixing ratios and meteorological parameters, such as wind speed and air temperature, were measured at three heights (0.75, 2, and 10 m) above the snow surface. Solar radiation at 0.50 cm was also measured. Using the flux-gradient method, ozone fluxes and dry deposition velocities can be calculated. The derivation of the ozone flux-gradient equation is presented here. Using a real data set, the ozone flux-gradient equation is illustrated. In addition to calculating ozone fluxes and dry deposition velocities in the arctic boundary layer, ozone mixing ratios were measured at the snow surface and within the snowpack. A distinctive dependency between snowpack ozone (also called firn air ozone) and photochemistry can be established, whereas the effect of wind seems to be to replenish the depleted ozone.
     In comparison, we also considered measuring ozone mixing ratio in the seasonal mid-latitude snowpack of Niwot Ridge, Colorado. A first campaign at Niwot Ridge, CO has been accomplished from January 20th to June 8th 2004, while a second campaign is in progress (goals are presented). Pairs of sampling inlets at 5 different levels (ground, 30, 60, 90, and 245 cm) on a 250-cm pole were mounted. The 245-cm pair of inlets sampled ambient ozone at all times during the entire winter. The other pairs of inlets gradually sampled ozone from the snowpack as snow accumulated during the winter. Until melting started, all the inlets within the snowpack sampled ozone below detection limit of the ozone monitor (i.e., 1 ppbv). This observation led us to hypothesize that the ozone loss could be due to reaction with the nitric oxide emitted by active microbiological population within the snowpack and/or at the soil surface. Also, the acidity of the snowpack (i.e., presence of nitrate ions) could also be contributing to some ozone loss.

Mar. 03      Nataly Ascarrunz, INSTAAR
"Precipitation effects on soil biogeochemistry: Moving dirt around eastern Bolivia."
     Since at least the industrial revolution atmospheric concentrations of carbon dioxide have been progressively on the rise. This shift in the chemistry of the atmosphere has begun to have significant impacts on global climate. Annual temperature averages have increased and a great deal of research has been focused on trying to predict further climate changes. One particularly interesting component of global climate change research focuses on investigating and predicting the possible feedbacks that changes in greenhouse gas concentrations could have on accelerating or impeding future atmospheric shifts. Studying the positive and negative feedback loops is an imperative component in forecasting future climate change and in investigating effective mitigation. One of the main predictions for climate change is that precipitation patterns will change across local, regional, and global scales. We believe that understanding how soil carbon turnover rates of tropical forests relate to changes in precipitation will be a key component of predicting and possibly mediating carbon cycle feedback loops to climate change. Due to the seasonal effect of the Intra-Tropical Convergence Zone (ITCZ), a natural precipitation gradient exists in eastern Bolivia running from the rainforests of Noel Kempff National Park in the north to the arid Chaco regions of the south. Using this gradient we can examine the interaction between precipitation and carbon turnover rates to gain insight into how changes in climate will impact the mechanisms that govern carbon sequestration and release.

Feb. 10      Kenneth Mack, INSTAAR
"A quick overview of a 5-box model for d13C-CH4 data to constrain methane source estimates."
     Methane is the second most potent greenhouse gas and is responsible for nearly 20% of the enhanced greenhouse effect. The most common means of estimating the source budget are through inverse modeling techniques using variations of the atmospheric concentration in space and time and by extrapolation of localized source flux measurements to a global scale. Yet, due to the wide array of methane sources and a relative paucity of measurements, its budget is not well constrained. Carbon-13 measurements offer a means to help clarify the methane budget because different groups of methane sources have distinct isotopic signatures. Since 1998, in co-operation with NOAA/CMDL, d13C-CH4 has been measured at the University of Colorado‚s Stable Isotope Lab from samples drawn on a weekly basis from select sites of the NOAA/CMDL Cooperative Air Sampling Network. We use a box model to simulate the effect that different methane source estimates would have on atmospheric CH4 and d13C-CH4 values at our measurement sites. We then compare the modeled d13C-CH4 values with d13C-CH4 data to evaluate those source estimates.

Jan. 27      Jessica Black, INSTAAR
"Sinking by iceberg, a hair-raising tale of survival on a barge, in the midst of a swarm of icebergs...(or - Holocene history of Hvítárvatn, Iceland)."
     More than 100 km of seismic reflection profiles of the sediment fill in the glacier-dominated lake Hvítárvatn, central Iceland, reveal over 65 m of stratified postglacial sediment in the main depositional basin. Five diagnostic seismostratigraphic units, defined on the basis of acoustic properties tied to lithostratigraphic breaks in sediment cores from the lake, can be traced throughout the sediment fill. Isopach maps of these units exhibit different spatial patterns, suggesting significant changes in the primary sediment delivery systems throughout the Holocene, and implying significant changes in the size and position of Langjökull. The mass of sediment in the lake is estimated to be between 35 x 1013 g and 121 x 1013 g. Suspended sediment loss from the lake currently averages 5 x 1010 g of fine sediment each year. The average Holocene bedrock erosion rate across the catchment is calculated to be between 2 and 5 cm ka 1, although actual erosion rates under Langjökull are probably much higher, whereas erosion across the non-glaciated portion of the catchment is presumably significantly less.

Jan. 13      Ryan Vachon, INSTAAR
"The Reality of High Altitude Ice Coring."
     The study of ancient climates gives us perspective on the magnitudes and the speed at which climate changes can occur. Some of the most robust and temporally resolute records have been recovered from ice cores in Polar Regions; however, there is a need to understand how climates change at low latitudes, where the bulk of the human population exists. This talk will outline the relevance of and the general techniques used in analyzing low latitude ice coring. It will end with a video documentary of a recent coring expedition into the Peruvian Andes.

Fall, 2004

Dec. 02      Wim Lekens, University of Bergen, Norway.
"Complex climate variations in a glacial world: examples from the southern Norwegian Sea."
     Recent core data from the southern Norwegian Sea and the Northern North Sea reveals a new and challenging view of the last glacial period in Fennoscandia. Sediment flux data and glacial reconstructions indicate a single strong glaciation period in Europe between 34 and 19 cal ka BP, compared to three phases in Eurasia. Along the northern European ice margin a strong coupling between Atlantic water inflow and ice margin destabilisation has been observed. Preliminary research shows unique manifestations for the most recent four Heinrich events and a significant input from the Norwegian margin during these events. The deglaciation of the Norwegian margin started around 19 cal. ka BP and initiated a rapid retreat of the Norwegian Channel ice stream, resulting in large melt water suspension plumes leading to rapidly deposited laminated sediments. A similar response was observed all along the Northern European margins leading a strong glacial retreat of the Laurentide ice sheet associated with Heinrich event 1 by 500 to 1000 yrs.

Nov. 18      Tim Tomaszewski, INSTAAR.
"Sprucing things up with foliar nitrogen spray at a Colorado subalpine forest."
     The influence of nitrogen (N) on upper canopy Engelmann spruce foliage was studied at the subalpine forest site below Niwot Ridge. During the growing season of 2004, three upper-crown branches from each of three spruce trees underwent an N-fertilization experiment. At each tree, a treatment branch received ammonium-nitrate (10-mg/l) in an ion-matrix solution that was representative of mean common ion concentrations for the site (estimated from NADP data). A control branch at each tree received only the ion-matrix solution (no N) and a background branch, at each tree, received only natural precipitation. Daytime and predawn chlorophyll fluorescence data were obtained for all branches: a) prior to the onset of foliar spraying and b) several times after each of 14 spray applications across the period from June through September 2004. Conifer foliage has been shown to take up wet deposited NH4+ directly from solution (Wilson 1992; Krupa 2003). Direct foliar uptake of NH4+ at rates exceeding the capacity for in vivo detoxification may damage foliage and reduce photosynthesis (Krupa 2003). Conversely, direct foliar uptake of NH4+ at rates below the capacity for in vivo detoxification may lead to elevated foliar N content and photosynthesis. Gas exchange data are still pending; however, preliminary fluorescence results will be presented.  

Oct. 28      Dylan Ward, INSTAAR.
"New constraints on the late Cenozoic incision history of the New River, Virginia."
      The New River crosses three physiogeologic provinces of the ancient, tectonically quiescent Appalachian orogen and is ideally situated to record the fluvial response to late Cenozoic climate variations. Active erosion features on resistant bedrock that floors the river at prominent knickpoints demonstrate that the river is currently incising toward base level. However, thick sequences of alluvial fill and fluvial terraces cut into this fill record an incision history for the river that includes several periods of stalled downcutting and aggradation. We used cosmogenic 10Be exposure dating, aided by mapping and sedimentological examination of terrace deposits, to constrain the timing of events in this history. Terrace surfaces were excavated and sampled for quartz sand at multiple depths, allowing construction of 10Be concentration depth profiles to help account for variables such as cosmogenic inheritance and terrace bioturbation. 10Be concentrations increase with terrace elevation above the river and decrease with depth in each deposit. Fill-cut and strath terraces at elevations 10, 20, and 50 m above the modern river yield cosmogenic exposure ages of 130, ~600, and ~950 ka, respectively, but uncertainties on these ages are not well-constrained. The new results provide the first direct constraint on the history of alluvial aggradation and incision events recorded by New River terrace deposits, and suggest that the river responds to external stimuli operating at timescales of 104-105 yr. The exposure ages yield a long-term average incision rate of 43 m/my, which is comparable to rates measured elsewhere in the Appalachians. During specific intervals over the last 1 Ma, however, the New River's incision rate reached ~100 m/my. Fluctuations between aggradation and rapid incision appear to be related to late Cenozoic climate variations, though uncertainties in modeled ages preclude direct correlation of these fluctuations to specific climate change events. Erosion rates on higher alluvial deposits adjacent to the river are estimated from 10Be concentrations; these rates are very low, about 2 m/my or less. This demonstrates a disequilibrium in the modern landscape, with river incision greatly outpacing erosion from nearby landforms.

Oct. 21     Sasha Reed, INSTAAR.
"Controls on nitrogen fixation in a tropical lowland rainforest, plus some video of Costa Rican wildlife."
     Nitrogen (N) is an important element in living organisms crucial to the formation of proteins, DNA, and enzymes to name a few. Nitrogen fixers (organisms that can use the large resource of nitrogen found as N2 in the atmosphere) are the link between atmospheric supply and biological demand. Current understanding suggests that rates of biological N fixation in tropical rainforests are among the highest for any biome. These high rates challenge our conceptual models of N fixation for two main reasons. First, tropical rainforests are the one major terrestrial region of earth where N frequently appears to cycle in relative excess, and high pools of fixed N are a known inhibitor of nitrogenase activity. Second, many tropical forests exist on highly weathered soils characterized by low phosphorous (P) availability, and several past studies suggest that P availability may constrain N fixation. Here I will report results for surveys of litter and soil N fixation rates in fertilization plots (N, P, N+P) located in Costa Rican tropical rainforests on P-poor soils. The sites are located in lowland forests on the Osa Peninsula of southwest Costa Rica, in a region that averages approximately 5m of precipitation per year. Acetylene reduction assay (ARA) measurements were conducted seasonally throughout a year in 40 plots that span four fertilizer regimes. Results showed that additions of P significantly increased N fixation rates for soil and litter communities, and that N fertilization, whether alone or in conjunction with P, did not significantly alter these effects. Additionally, litter N fixation rates were orders of magnitude higher than analogous soil rates. Finally, strong seasonal patterns were observed, highlighted by N fixation rates that were several-fold lower in all plots during the short dry season. I plan on discussing this research for a portion of the time and then showing a 10-15 minute video of a bunch of videos of the Osa spliced together (tapirs/monkeys/etc).

Oct. 14    Trevor Popp, INSTAAR.
"North Greenland Ice Core Project (NGRIP): New results from 2004 and fingerprinting abrupt climate change."
     As of August 2004 the NGRIP deep ice core drilling program is terminated and camp is officially closed. I will share the results of reaching bedrock, not only once, but twice, more than 3090 meters below the surface at NGRIP. Upon reaching bedrock in 2004 we not only extended our undisturbed Greenland climate record futher into the last interglacial than any other Greenland ice core, we may have collected ancient organic material from the basal sediments. I will also present our latest high resolution results across some of the largest and most abrupt climate changes recorded in the NorthGRIP climate record.

Sep. 16     Hans-Peter Marshall, INSTAAR.
"Measurements of snow stratigraphy using high frequency microwave
radar at the Swiss Federal Institute for Snow and Avalanche Research (SLF)."
     Alpine snowpacks are known to have large variability, both spatially and temporally on a wide range of scales. Stability measurements are made at many different length scales, however the most important length scale for the avalanche formation process is still largely unknown. In addition, avalanche forecasters and practitioners typically have detailed snowpack measurements from only a few locations, and must extrapolate observations over large areas. Radar is a promising tool for snowpack studies, as large areas can be covered rapidly and at high resolution. In addition, the technique is non-invasive so that temporal variations can be automatically monitored.
      This talk presents results from measurements made in Davos, Switzerland, while I was a visiting graduate student at SLF last winter.

Spring, 2004

Apr. 29     Carl Bern, INSTAAR
"Biogeochemistry, isotopes, and tectonics in Costa Rica."
     Controls over nutrient supply are key to understanding the structure and function of terrestrial ecosystems. Conceptual models once held that that in-situ mineral weathering was the primary long-term control over the availability of many plant nutrients, including the base cations calcium (Ca), magnesium (Mg), and potassium (K). Recent evidence has shown that atmospheric sources of these "rock-derived" nutrients can dominate actively cycling ecosystem pools, especially in systems on highly weathered soils. Such studies have relied heavily on the use of strontium isotopes as a proxy for base cation cycling. Here we show that vegetation and soil-exchangeable pools of strontium in a tropical rainforest on highly weathered soils are still dominated by local rock sources. This pattern exists despite substantial atmospheric inputs of Sr, Ca, K and Mg, and despite nearly 100% depletion of these elements from the top 1 m of soil. We present a model demonstrating that modest weathering inputs, resulting from tectonically driven erosion, could maintain parent-material dominance of actively cycling Sr. The majority of tropical forests are on highly weathered soils, but our results suggest these forests may still show considerable variation in their primary sources of essential nutrients.

Apr. 15     Rose Cory, INSTAAR
"Explanation of the Fluorescence Index." 
      McKnight et al. (2001) developed a parameter termed the fluorescence index (FI) to determine the source of dissolved organic matter (DOM). The fluorescence index is the ratio of emission intensities at 450 over 500 nm, for an excitation of 370 nm. A higher fluorescence index (~2) corresponds to DOM with a greater fraction of microbial organic matter; an FI around 1.2 corresponds to DOM dominated by terrestrial inputs of organic matter. The FI has been used widely to examine seasonal changes in DOM, to understand the effects of anthropogenic nutrient inputs into aquatic ecosystems, and to understand the effects of photobleaching on DOM. Using recently developed fluorescence modeling techniques, we have identified two fluorophores that explain the FI (see figure below). In addition, there is strong evidence that the fluorophores identified are specific quinones. The implications of these findings for using fluorescence as a tracer for DOM source and reactivity will be discussed.

Apr. 08     Shad O´Neel, INSTAAR
"Force balance analysis at Columbia Glacier."
     Tidewater glaciers are known to undergo cycles of slow advance and rapid retreat (Post, 1975). A mass balance deficit may initiate the retreat, but observational and modeling evidence suggests that retreats are largely controlled by factors other than climate forcing. During retreat phase, a tidewater glacier may retreat on the order of 1-2 km per yr, concurrent with dramatic increases in ice velocity. Analysis of forces that both propel and restrain tidewater glaciers and the evolution of forces through a retreat provide insight into the processes governing retreats. I will talk about how to get at these forces and their implications for Columbia Glacier in Alaska.

Apr. 01     Jan Pollman
"Development of a method for the analysis of sesquiterpenes in ambient air."
      Sesquiterpenes (C15H24, SQT) are semi-volatile organic compounds emitted from vegetation. SQT are of high scientific interest because of their role in attracting flower pollinators or in plant defense responses against herbivores. They are also suspected to play a major role in the formation of secondary biogenic aerosol and are therefore of interest for air-quality research. Analysis of SQT in air poses a series of challenges that stem from the semi-volatile and highly reactive properties of these compounds. To date SQT-emission rates remain highly uncertain. Some estimates show that SQT-emissions may account for up to 20% of the total biogenic emitted carbon. Therefore it is of high importance to improve our knowledge of these compounds. We have developed techniques for the study of SQT emission rates and landscape fluxes in different environmental experiments. The analysis method is based on solid adsorbent sampling with subsequent thermal desorption as well as gas-chromatography and flame-ionization-detection. SQT emission studies on natural, urban and agricultural vegetation are now in preparation.

Mar. 04    Trevor Popp, INSTAAR.
" Blue ice at Mt. Moulton, West Antarctica: Weaving together half of a million years of climate using a volcanic clock."
     At Mt. Moulton in West Antarctica the history of the volcano and the climate are laid bare on the surface near the summit in exposed blue ice and parallel tephra layers that date from 10,000 to 492,000 years ago. During the 1999-00 Antarctic field season a group of US scientists cut a continuous horizontal ice core across the blue ice field using chainsaws. Subsequent analysis of the ice revealed a climate record similar to others in the region, but with the promise of an absolute time scale using radiometric dates from the interlaced tephra. We returned to Moulton for the 2003-04 Antarctic field season to refine our record. I will present our progress and the story of our deep field experience.

Fall, 2003

Dec. 04     Kari-Lise Rorvik, University of Tromsø.
"Last Glacial Maximum: a high resolution record from isotope stage 2 in the NE Nordic Seas."
     We have investigated one high resolution sediment core (MD99-2294) penetrating the Lofoten Contourite Drift situated at the continental slope off Lofoten, Northern Norway in the northeast Atlantic. Our main focus is on the paleoceanography and glacial history in this area during the Last Glacial Maximum (LGM, 19,3-16,7 BP?) based on analyses of foraminiferal faunas, stable isotopes, ice-rafted debris and radiocarbon dates.

Nov. 20     Keri Holland, INSTAAR.
"Short-term fate of nitrogen in alpine tundra."
     Despite recent interest in understanding the effects of nitrogen (N) deposition on alpine ecosystems, we lack key mechanistic understanding about the fate of excess N in these systems. In 2000, a stable nitrogen isotope tracer was applied to a series of long-term low-level N only and high-level nitrogen and phosphorus fertilization plots on Niwot Ridge, in the Colorado alpine. Preliminary delta15N data from bulk soil and plant pools suggest that plants dominated N uptake over the first two growing seasons.

Nov. 13     Ryan Vachon, INSTAAR
"Stories from the Drop: Stable isotopes of precipitation."
     Stable isotopes of precipitation are the primary proxy for interpreting many paleoclimate records, and they tell us a lot about the hydrologic cycle for given regions. I hope to shed some light on meteorological and geographic parameters affecting the stable isotopes of precipitation within the United States.

Nov. 06     Hans-Peter Marshall, INSTAAR
"High Frequency Radar measurements and slope stability modeling in alpine snowpacks: development of tools for avalanche prediction and snow hydrology."
     High Frequency (2-18 GHz) ground based FMCW radar measurements were made in 4 very different alpine snowpacks during last winter as part of the NASA Cold Lands Processes Mission (CLPX). This type of radar system uses a very broadband signal, which gives a vertical resolution of ~ 1.5cm. The measurement and processing techniques used will be discussed, and the results related to manual measurements of snowpack properties (density,grain size, hardness profiles, etc) and in-situ dielectric measurements using the Finish snowfork.
     The system used last winter was ~300 lbs and therefore profiles of only several meters were made from a tripod, however a small handheld system has now been built and will be used this winter to study spatial variations over large distances and within avalanche terrain. These measurements, coupled with time series measurements made at a stationary site will be encorporated into a snow slope stability model, since the radar measurements will give information about layer thickness/density changes over space and time.

Oct. 23     Rose Cory, INSTAAR.
"Microbially-mediated ferric iron reduction in Nymph Lake, Colorado."
      Fluorescence spectroscopy was used to examine the redox state and chemical character of dissolved organic matter (DOM) in Nymph Lake, a seasonally ice-covered lake in Rocky Mountain National Park, CO. Water samples were collected monthly beneath the ice in Nymph Lake from December through April, 2002/2003. A sample was also collected in June, 2003 when the lake was ice free and well-mixed. Excitation-emission matrices (EEMs) of the filtered water samples show that the dissolved organic matter became increasingly reduced as the winter season progressed. In contrast, the EEM of the June sample is consistent with a shift to oxidized DOM. A systematic shift in the EEMs towards an increasingly reduced signal, combined with trends in dissolved oxygen, ferrous and ferric iron concentration, and Eh potential strongly suggest that DOM serves as an electron shuttle for microbially-mediated ferric iron reduction under the ice in Nymph Lake. To confirm the oxidation state of DOM, laboratory experiments were conducted by adding ferric citrate to the water samples collected in March. Addition of oxidized iron caused an increase in the reduced iron concentration and a shift in the EEMs consistent with DOM oxidation. The potential implications of this process on nitrogen cycling will be discussed. 

Oct. 09     Ken Mack, INSTAAR.
"Constraining the Budget: The measurement of deltaD of atmospheric methane"
     Methane (CH4) is an infrared absorber and acts as a greenhouse gas in the atmosphere. Atmospheric CH4 is the second most potent of the anthropogenic greenhouse gasses and accounts for nearly 20% of the enhanced radiative forcing since 1750 over which period the concentration has increased nearly two and a half times. It is accepted that the increase is due to human influence on the source through rice and livestock agriculture, and the extraction of fossil carbon. Yet, despite increasing population and industrial production, the CH4 growth rate has decreased since the mid 1980s. The recent trend is not well understood despite efforts that have been made to constrain the CH4 budget. Isotopes can help further constrain the CH4 budget by acting as tracer of certain source and sink processes. To help further refine the budget we plan to measure the deuterium isotopes of CH4 (deltaCH3D) at high spatial and temporal resolution. To do so we will construct the instrumentation and develop a method for the measurement of the deltaCH3D.

Sep. 25     Florence Bocquet, INSTAAR.
"Photochemical ozone loss in snow at Summit, Greenland."
     This summer was the first phase of a three-year investigation of ozone fluxes in the atmospheric boundary layer over permanently covered snowfields, like Greenland. Sensitive techniques have been employed to measure ozone gradients, which are in the order of tenths parts per billion volume (ppbv) from a research tower. Firn air measurements were performed for the study of the processes leading to ozone deposition to snow. In this presentation, pictures of this summer's field season will be shown, and first few results of ozone flux and firn air data will be presented. Emphasis will be on the ozone in the firn air, which was found to exhibit distinctive diurnal cycles, and which are well correlated with solar radiation and wind speed.

Sep. 18     Rose Cory, INSTAAR.
"Preliminary results from the 2003 Alaskan Field Season: Effect of dissolved organic matter on the indirect photolysis of persistant organic pollutants."
     During both the 2002 and 2003 field seasons, dissolved organic matter (DOM) was isolated by XAD8 from several lake, stream and marine sources in the Alaskan Arctic at the Toolik Lake LTER. Elemental analysis, UV/VIS and fluorescence have been used to study the chemistry of the DOM. Starting in the 2003 field season, photodegradation experiments were conducted in the Arctic to investigate the ability of DOM to indirectly photodegrade persistent organic pollutants (POPs). Quartz tubes containing a known concentration of the POP and DOM were placed in the natural sunlight for 24 hour. The decrease of the POP concentration was measured during that period. Quartz tubes containing DOM only were also irradiated in order to investigate the change in DOM chemistry during photolysis. Preliminary results demonstrate that the photodegradation of certain POPs is enhanced in the presence of DOM. In addition, the rate and extent of POP breakdown is a function of the chemical character of the DOM. Specifically, the breakdown of the POPs is related to the initial C:N ratio of the DOM as well as the fluorescence index (FI). Initial results from the DOM-only photolysis experiments reveal a sharp decrease in the FI within the first four hours of irradiation, after which there is only minimal change in the FI. Ultimately, the goal of this study is to identify a mechanism for the DOM mediated photodegradation of the POPs.

Sep. 11     John Ortega, INSTAAR.
"Biogenic flux measurements at a northern mixed hardwood forest."
     In addition to exchange of H2O, CO2 and O2 between vegetation and the atmosphere, plants can emit a variety of other biogenic volatile organic compounds (BVOC). On a global scale, BVOC emissions exceed anthropogenic sources by at least five times. BVOC continue to receive scientific interest for several reasons:
     . they affect the oxidative capacity of the troposphere,
     . they contribute to atmospheric chemical reactions leading to tropospheric ozone formation,
     . they are components of organic aerosols (e.g. monoterpenes, sesquiterpenes),
     . they can provide sensory cues to insects for pollination and for tri-trophic interactions,
     . they can be a significant loss of carbon that is not taken into account in most measurements involving biometric or carbon flux measurements.
     Global change has the potential to have significant impacts on BVOC emissions. However, there is much uncertainty about how the combined effects of changes such as elevated CO2 and ozone levels, higher temperatures, land use changes, longer growing seasons, defoliation events, and related feedbacks will affect future emissions. Accurate measurements of BVOC landscape fluxes are challenging because of low ambient mixing ratios in air (low ppb to ppt), short atmospheric lifetimes and analytical measurement limitations. It is desirable to obtain fast (10 Hz) real time eddy correlation measurements of BVOC fluxes, but other techniques are necessary when ambient concentrations are too low or instrumentation limitations prevents these rapid measurements. Some of these techniques include vegetation enclosure experiments and above canopy flux measurements using relaxed eddy accumulation and disjunct eddy accumulation.
     This talk will provide an introduction to some of the methods used to make biogenic flux measurements and some preliminary results from the 2003 summer season at a northern mixed hardwood forest.

Sep. 04     Trevor Popp, INSTAAR.
"Ice core to bedrock at NorthGRIP, Greenland: Last Interglacial ice and subglacial water."
     This summer an international ice core drilling team successfully reached bedrock at NorthGRIP, culminating a seven year effort. The 3085 meter ice core offers a new highly detailed climate archive of the last glacial cycle, including the termination of the last interglacial period approximately 120,000 years ago. Upon reaching the base of the ice sheet, we had the pleasant surprise of obtaining a sample of subglacial water, a potential boon for microbial biologists and geochemists, among others. In this presentation I will share the excitement through slides of how we did this and preview how our results may advance our understanding of the climate system.

Spring, 2003

Mar. 06    Thomas Hoffmann, Department of Geography, University of Bonn, Germany, "Modelling the Holocene sediment budget of a large-scale fluvial system (Rhine River)."
     With respect to the increasing tendency of extreme floods, it becomes necessary to evaluate the relative influences of climate versus land-use changes on fluvial systems. Hence, the aim of the LUCIFS Project is to clarify the “Land Use and Climate Impacts on Fluvial Systems during the period of agriculture”. I state that a dynamical (long-term) sediment budget model can enhance understanding the non-linear response of Rhine system to the interacting changes of land use and climate. However, the model has to cover
     (i) the large spatial scale of the Rhine catchment (185.000 km^2),
     (ii) a long temporal scale (period of agriculture started 7000yr BP),
     (iii) and multiple geomorphological processes (fluvial and slope processes) which act within the catchment.
Existing sediment-transfer models are mostly to complex and parameter demanding to satisfy the above mentioned points. To model the entire Rhine catchment a simple empirical model is needed. The gap between complex, numerical sediment-transfer models and a simple, empirical sediment-budget model can be closed by a combination of the two approaches for medieval scales. The validation of the models can be achieved by down- and upscaling of the scale-dependant models. To solve the scaling issues a nested model hierarchy is needed.

Feb. 27     Natalie Mladenov, INSTAAR, "Sources, transport and chemical quality of dissolved organic carbon in a large annually flooded wetland, the Okavango Delta, Botswana."
      Large arid zone wetlands, such as the 15,000 km2 Okavango Delta in northwest Botswana, serve as essential habitats for unique and endangered species of plants and animals and are important players in the global carbon cycle. The Okavango Delta maintains a delicate balance of water and nutrients, including an annual flooding event which brings much needed water during the dry season and which flushes organic matter (OM) into the water column, making it available for decomposition, a necessary basic step in food web dynamics.
     In surface waters of the seasonal swamp of the Okavango Delta, DOC concentrations peak during the rising limb of the annual flood and decrease when flood stage is at its highest. DOC concentrations in riverine and permanently flooded areas were on the order of 2 to 5 mg C/l, while DOC in seasonally flooded areas was as high as 28 mg C/l. An evaluation of DOC-flow-conductivity relationships suggest that the decrease in DOC concentration in the seasonal swamp at peak flood is partially due to a ìdilutionî effect. Additionally, aquatic food web studies indicate that low DOC concentrations following the flood are due to a ìconsumptionî effect from organisms grazing on newly released organic matter. Results from spectrofluorometric analyses of spatial and temporal samples indicate that the increase in organic matter concentrations in seasonally flooded areas is due to flushing of terrestrially-derived OM. The quality of OM in permanently flooded areas was shown to be more microbial in origin.

Feb. 20    Jessica Black, INSTAAR, "Can a Little Ice Age climate signal be detected in the Southern Alps of New Zealand?."
      The Little Ice Age (LIA) was a late Holocene interval of climate cooling registered in the North Atlantic region by expansion of alpine glaciers and sea ice. Here the LIA includes an early phase from about AD 1280 to AD 1390, along with a main phase from about AD 1556 to AD 1860, followed by warming and ice retreat. It has recently been demonstrated from records of North Atlantic ice-rafted debris that the LIA is the latest cooling episode in a pervasive 1500 yr cycle of the climate system that may lie at the heart of abrupt climate change. This raises the question of whether the LIA climate signal is globally synchronous (implying atmospheric transfer of the climate signal) or out of phase between the polar hemispheres (implying ocean transfer of the climate signal by a bipolar seesaw of thermohaline circulation). New Zealand is ideally situated to address this problem as it is located on the opposite side of the planet from the North Atlantic region where the classic LIA signal is registered so clearly.
     Due to high precipitation and ablative activity gradients, glaciers in the Southern Alps of New Zealand respond to climate change on a decadal timescale. Therefore, moraine sequences deposited during oscillations of these glaciers are ideal for determining the character of the LIA signal in this portion of the Southern Hemisphere. The chronology of the late Holocene moraine sequences fronting Hooker and Mueller Glaciers in the Southern Alps is controversial. Initial dating of these moraines from historical records, as well and from lichenometric and tree-ring analyses, pointed to deposition in the LIA, indicating a globally synchronous climate signal. In contrast, a subsequent chronology based on weathering rinds of surface clasts suggested that most of the late Holocene moraines antedate the LIA, implying lack of a classic LIA climate signal in this portion of the Southern Hemisphere. To resolve this dilemma, a new and detailed chronology of the Hooker and Mueller Holocene moraine systems was constructed in this study by using geomorphologic maps, historical records, and the FALL lichenometry technique.
     A major result of this study is that most of the Holocene moraines fronting the Mueller and Hooker Glaciers were deposited during the main phase of the LIA as defined in the North Atlantic region. The glacier advances recorded by these moraines are about equivalent in age with those in the North Atlantic region. The magnitude and timing of the LIA climate signal is nearly the same in the two regions. The collapse of the Hooker and Mueller Glaciers in the last 140 years is also approximately synchronous with retreat of glaciers in the North Atlantic region. Therefore, the LIA climate signal occurs in the atmosphere as far south as New Zealand, on the other side of the planet from the North Atlantic region.

Jan. 23     John Ortega, INSTAAR, "Biogenic emissions of Volatile Organic Compounds: A Practice talk for my upcoming oral comprehensive exam to my department (PAOS)"
     Volatile Organic Compounds (VOCs) exist at trace levels in the atmosphere and have varied temporal and spatial distributions with atmospheric lifetimes that range from seconds to years. The majority of the volume of VOCs are not of anthropogenic origin, but are actually emitted by vegetation. Photochemical reactions involving oxides of nitrogen (NOx) and VOCs contribute to the formation of atmospheric pollutants including ozone and aerosols. Therefore, strategies to control air quality can be difficult to develop in heavily forested areas. This talk first presents much of what is already known about the sources and distributions of biogenic VOCs (BVOCs) including the various types of compounds emitted, their diurnal, seasonal, other environmental trends, the types of vegetation that emit certain gasses, and some chemical reactions. Then, two measurement methods for determining landscape fluxes of BVOCs will be discussed:
1. Disjunct eddy correlation using ion trap mass spectrometry, and
2. Branch enclosure measurements using adsorption cartridges followed by analysis by gas chromatography and mass spectrometry.
Measurements from recent research will be presented with analysis of the emission rates, landscape fluxes and associated uncertainties.

Fall, 2002

Dec. 12     H.P. Marshall, INSTAAR, "Avalanche science: How can ground penetrating radar and finite element models further our understanding of snow slope stability?"
      Spatial variation in snowpack strength properties is one of the most important but poorly understood problems in snow avalanche research. A backcountry skier or avalanche technician typically digs a snowpit and performs various tests to determine stability, then uses weather info, experience, terrain info, etc to extrapolate over a large area. The strength properties are known to vary widely however; digging another nearby snowpit often produces different results, and shear strength tests are known to vary as much as 50% in a seemingly homogeneous layer of snow. This talk discusses this problem and introduces two methods of potentially improving our understanding of this spatial variation and its influence on the snowpack. A finite element model using interface elements is being developed to describe the transfer of stress from weak to strong areas. Ground penetrating radar experiments in an alpine snowpack are also underway, to try to develop a method for remotely estimating the magnitude of this variation.

Nov. 07     James Syvitski, INSTAAR Director, "The art and science of journal publishing."
     A detailed outline is posted at http://instaar.colorado.edu/other/grad_talks_syvitski.html
     The presentation is posted at http://instaar.colorado.edu/deltaforce/startpages/pictures/writing_a_paper.htm

Oct. 17     Meredith Newman, INSTAAR visiting Scientist, Associate Professor of Chemistry and Geology, Hartwick College, Oneonta, NY, "What’s it like to teach?"
     This presentation is somewhat different from the rest. It does not present research results. As many of you may be considering careers as college professors, I thought you might like to here what is involved in getting and succeeding at a teaching position at a small liberal arts college. I will share my experiences of applying for, working at, hiring new faculty for, and serving on the tenure and promotion committee at Hartwick College. Hartwick is a liberal arts college of approximately 1500 students.

Oct. 03     Sarah Principato, INSTAAR, "Glacial geology on the NWP, Iceland: 2002 Field Results."
      Terrestrial geomorphic mapping of part of the Northwest Peninsula of Iceland is in progress to address questions regarding ice extent and glacial history during the last glacial maximum and through the deglaciation and the Holocene. Distinct erosive glacial landforms including, cirques, artes, horns, and u-shaped valleys dominate the northwest and southeast sections of the study area. These features vary in elevation from approximately 500 to 780 meters above sea level. The presence of striations and grooves indicates that this area was probably glaciated by warm based ice. A Geographic Information System (GIS) is used to map lake density, which is interpreted as a proxy for the degree of ice scour over the landscape. A 10km by 10km grid, superimposed over the hydrography coverage, shows that lake density varies from zero percent up to 8.8% of the land area. Lake density is the highest in the regions of former ice centers over Glama and on the upland from Steingrimsfjardarheidi to Ofeigsfjardarheidi. Additional calculations using the GIS software, such as the relationship of lake density to the topography and distance to the coast, are in progress. Chlorine-36 cosmogenic isotope exposure dating is used to determine the ages of some of these erosive glacial landforms, and preliminary age calculations appear too old.
     Evidence for Holocene glacial activity is concentrated in valleys currently occupied by outlet glaciers of the Drangajokull Icecap. Sequences of moraines in Kaldalon, Leirufjordur, and Reykjafjordur are mapped and show at least five episodes of glacial advance. A radiocarbon date of 3328+/- 45 14C years on wood at the base of a peat section on top of the second outermost moraine in Kaldalon provides a minimum age for Neoglacial activity in this valley. Dates from peat sections are supplemented by lichenometry measurements of Rhizocarpon gr. geographicum on younger, less well vegetated moraines in Kaldalon. These measurements yield relative ages of the glacier fluctuations during the past few hundred years and are correlated with the Little Ice Age. Cosmogenic exposure ages on the boulders from the crests of the outermost moraines in Kaldalon and Leirufjordur are pending.

Sep. 26     Rose Corey, INSTAAR, "The concentration and composition of soil water dissolved organic matter across Olympic National Park, WA."
     Dissolved organic carbon (DOC) concentration and dissolved organic matter (DOM) composition were investigated at two depths in the soil: 15 and 40 cm. In addition, the effect of increased nitrogen availability on soil water DOC concentration and DOM composition was tested. Forested plots covering a gradient of precipitation, climate, slope and aspect in Olympic National Park were fertilized with the addition of 20, 10 and zero (control) kg urea-N ha-1 y1. A total of eleven sites were established within the park. Seven sites had the two different fertilizer treatments and control plots, while the additional four sites had no fertilizer treatments. Soil water DOC concentrations ranged from 0.5 mg C/L to 54.1 mg C/L, with an average value of 14.1mg C/L. DOM composition was examined as a function of molar ratios, H:C, O:C and N:C, index of unsaturation, average carbon oxidation state, and specific absorbance. Fertilizer had no consistent effect on either DOM concentration or composition across study sites at the Park. Soil depth influenced both DOM concentration and composition. Shallow soil water samples had greater DOC concentrations, higher specific absorbance, were more unsaturated and had lower molar ratios compared to deep soil water samples. Overall, changes in DOM stoichiometry and light absorption as a function of soil depth were consistent despite the diversity of the forested study sites sampled.
     I'll also talk briefly (and show some pictures) about my new PhD research on DOM at Toolik Lake LTER in Alaska.

Sep. 19     John Ortega, INSTAAR, "Biogenic emissions of Volatile Organic Compounds: 2002 summer field session at the University of Michigan Biological Station."
     It is well documented that the earth is experiencing altered atmospheric conditions (higher CO2 levels, higher temperatures, changes in precipitation patterns) which can profoundly affect living organisms and the ecosystems they inhabit. In the spring of 2002, I received an IGERT fellowship award called BART: Biosphere Atmosphere Research and Training. This is an NSF IGERT program (based in Michigan) designed for graduate students to learn about and perform research in biosphere atmosphere interactions. This past summer was the first that I spent at the University of Michigan Biological Station (UMBS) studying fluxes of biogenic Volatile Organic Compounds (VOCs). These VOCs are major contributors to the formation of ozone and particulates in the lower troposphere. Emissions from vegetation can be significant contributions to the total VOC emissions, especially in densely forested landscapes. Therefore, investigating biogenic VOC sources is important in advancing our understanding of air quality and tropospheric chemistry.
      In this talk, I will give show some pictures of UMBS, provide some background into traditional chemical analysis of VOCs and introduce two methods that I am using for measuring biogenic VOC emissions and fluxes:
1. Collecting air samples for branch enclosures on solid adsorbent cartridges with subsequent VOC analysis using gas chromatography/mass spectrometry for separation and compound identification. Quantitative emissions rates are determined using a flame ionization detector.
2. Disjunct Eddy Sampling using sample collection/enrichment apparatus and an Ion Trap Mass Spectrometer for quantitative analysis. A sonic anemometer is used to determine wind speeds/directions for flux calculations from disjunct samples.

Sep. 12     Johan Temnerud, Rebro University, Sweden, "Spatial variation of dissolved organic carbon (DOC), an example from Northern Sweden.
Johan.Temnerud@nat.oru.se
There was some evidence that the headwater streams could have higher amount of DOC than downstream in Swedish boreal catchments. To check this "hypothesis" every stream junction in a 70 km2 boreal catchment in Northern Sweden was sampled. First sampling period was in the beginning of June 2000 and the second period was this past August. Both periods were chosen because it was desribale to have a stable, low flow condition. We found a large variation in the headwater, year 2000 = 2-38 mg/l DOC (n = 61), year 2002 = 4-67 mg/l DOC (n = 67). Those concentrations even out downstream so the outlet had year 2000 15.3 mg/l DOC and year 2002 14.7 mg/l. Only by mere conservative mixing with ground water, with low amount of DOC, could we explain that the concentrations even out. Of course this does not, in any way, roll out in-stream processes like precipitation, or degradation by light and micro-organisms. Normalizing for volume of water, headwater streams had higher amounts of DOC than downstream. For year 2000 this hypothesis seems like it was correct, and I'm working on the results for year 2002.
      DOC has a great impact on water ecology, both water chemistry, biota and the structure of streams. So how will these DOC-variation influence the biota and the water chemistry in a catchment? These patterns raise another question: What is normal levels of DOC in boreal Swedish catchment?

Spring, 2002

May 02     Irina Overeem, INSTAAR Post Doc "The Late Cenozoic Eridanos delta system in the Southern North Sea Basin: a climate signal in sediment supply?"
      IRINA OVEREEM1, GERT JAN WELTJE2, CHRISTINE BISHOP-KAY3 SALOMON B. KROONENBERG2
1 Institute of Arctic and Alpine Research
2 Department of Applied Earth Sciences, Delft University of Technology, The Netherlands PO Box 5028, NL-2600 GA Delft, The Netherlands. E-mail: i.overeem@ta.tudelft.nl
3 Woodside Energy Ltd, 1 Adelaide Terrace, Perth WA 6000, Australia
      The Eridanos fluvio-deltaic system, draining most of northwestern Europe, developed during the Late Cenozoic as a result of simultaneous uplift of the Fennoscandian shield and accelerated subsidence in the North Sea Basin. This seismo-stratigraphic study aims to reconstruct the large-scale depositional architecture of the deltaic portion of the basin fill and relate it to external controls. A total of 27 units has been recognised. They comprise over 62x10^3 km3 in the Southern North Sea Basin alone, and have an average delta surface area of 28x10^3 km2, which suggests that the size of the drainage area was about 1.1x10^6 km2. Water depth in the depocentre is seen to decrease systematically over time. This trend is interrupted by a deepening phase between 6.5 and 4.5 Ma, that can be correlated with the simultaneous occurrence of increased uplift of the Fennoscandian shield, increased subsidence of the southern North Sea basin, and a long-term eustatic highstand. All of these observations point to a tectonic control on long-term average rates of accommodation and supply. Controls on short-term variations are inferred from variations in rates of sediment supply and bifurcation of the delta channel network. Both rates were initially low under warm, moist, relatively stable climate conditions. The straight wave-dominated delta front gradually developed into a lobate fluvial- dominated delta front. Two high-amplitude sea-level falls affected the Pliocene units, which are characterised by widespread delta-front failures. Changes in relative sea level and climate became more frequent from the Late Pliocene onward, as the system experienced the effects of glacial-interglacial transitions. Peaks in sedimentation and bifurcation rates were coeval with cold (glacial) conditions. The positive correlation between rates of supply and bifurcation on the one hand, and climate proxies (pollen and d18O records) on the other hand is highly significant. The evidence presented in this study convincingly demonstrates the control of climate on time-averaged sediment supply and channel-network characteristics, despite the expected non-uniformity and time lags in system response. The presence of a clearly discernible climate signal in time-averaged sediment supply illustrates the usefulness of integrated seismo-stratigraphic studies for basin-wide analysis of delta evolution on geological time scales.

Apr. 25       Greta Bjork Kristjiansdottr, INSTAAR, "Late Quaternary sediment deposition in Eyjafjardaràll, N Iceland shelf: what the heck happened in the early Holocene?"
      Sedimentological and geochemical variations in four marine sediment cores, B997-319PC2, B997-319GGC, B997-317PC1 and B997-321PC from Eyjafjar¦aràll trough were studied. The cores contain two main lithofacies, olive-green mud and grey mud, interpreted as modern marine sedimentation and glacialmarine sedimentation respectively. Between them lies a transitional zone with a high content of sand and some granules. A large gap in radiocarbon age is found across the transition zone, indicating disturbances in the cores and possibly loss of all early Holocene sedimentation. The dating and cause of this hiatus is still an issue, so any suggestions or comments will be welcomed.

Apr. 11      Steven DeVogel, INSTAAR, "Paleo-lake Levels of Lake Eyre, Australia: Reconstructed using GIS"
      The largest lake in Australia, Lake Eyre, is a closed-basin lake which receives the vast majority of its moisture from summer monsoon precipitation. It is believed that the monsoon experienced times of greater intensity during the Last Interglacial. Numerous shoreline deposits around Lake Eyre strongly support this hypothesis. In this project, a digital elevation model was used to fill Lake Eyre to a paleo-shoreline and to calculate area and volume of that mega-lake system. A much larger, perennial Lake Eyre would likely have been a positive feedback for precipitation over the interior of Australia. This provides an important detail concerning Australian paleoclimate.

Apr. 04      David Mixon, INSTAAR, "In search of the lost reservoir: an adventure in GIS."
      During the past three years, I've been looking for a few good reservoirs. In order to make use of a dusty government database containing rates of sedimentation for over 1,800 U.S. reservoirs it has been necessary to spend a significant amount of time developing a method to "find" these reservoirs. Once located, the watershed for each reservoir is delineated and characterized by a geographic information system (GIS). These watershed descriptions have lead to some important conclusions about the nature of reservoir sedimentation in the U.S. Ultimately, these conclusions will be used for the development of a series of empirical models to predict sedimentation rates in the tens of thousands of unmeasured reservoirs in the U.S. These predictions will have important applications in sediment and nutrient cycle (esp. carbon) studies.

Feb. 14     Laura Belanger, INSTAAR, "Acid mine drainage, Snake River Watershed, Summit County, Colorado."
      I will be presenting some of the findings of my master's research on acid rock draining in the Snake River Watershed, Summit County, Colorado. The purpose of this study was to distinguish between watershed and instream controls on acidity, metal concentrations and mass-flows for both the natural weathering of disseminated pyrite and anthropogenic point source mines.

Jan. 24     Francesca Smith, INSTAAR, A mock dissertation defense: "The record of ancient grasslands held in the carbon isotope signature of fossil phytoliths (silica bodies made by grasses)"
     I have been a visiting graduate student at INSTAAR for years, but am a student at the University of Chicago. I will be defending my dissertation there, but wanted to give a defense-like talk at INSTAAR. My research focuses on the carbon isotope signature of both modern and fossil phytoliths (silica bodies produced by grasses) as a means of reconstructing the photosynthetic pathway (C3 or C4) of ancient grasses. I am interested in the Neogene (Miocene and Pliocene- 2-23 milion years ago) because during this period there was a global expansion of C4 plants. Other methods of reconstructing past vegetation are unable to discern between grasses and shrubs and trees. Thus, in order to examine the record of grasses specifically, I have worked on developing this method (carbon isotope measurements of organic carbon in fossil phytoliths)

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