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Selected Abstracts
INSTAAR Grad Student Talks

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• INSTAAR Grad Student Talks

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, ultimate