INSTAAR Grad Talks-Abstracts

Selected Abstracts
INSTAAR Grad Student Talks

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INSTAAR Grad Student Talks

Spring 2012

Feb. 09 Phil Taylor, INSTAAR.
"Rainforest carbon sequestration."

Rainforest growth buffers atmospheric CO2 rise, yet even remote regions are under threat from climate change. I will overturn the conventional notion of climate regulation of long-term rates of productivity by showing that the wettest of tropical realms are hotspots of carbon sequestration. Scaling shows that process models and satellite-based methods dramatically underestimate the role of intact tropical rainforests in the global carbon cycle. Should these approaches be adopted within policy mechanisms aimed at curbing CO2 emissions, rainforests will be devalued to the detriment of humans and ecosystems alike.

Fall 2011

Nov. 17 Caroline Alden, INSTAAR.
"Inverting 13CO2 for terrestrial carbon fractionation in North America"

The stable isotope of Carbon, 13C, has been used globally to partition ocean from terrestrial CO2 fluxes, and regionally as an indicator of C3 plant discrimination and the relative abundances of C3 and C4 vegetation. In North America, the spatial and temporal density of atmospheric observations enables, for the first time, inversions of land surface fluxes of CO2 and the 13C signature of those fluxes (multiplied together: isofluxes). The traditional Bayesian inversion is performed in two steps: first, we optimize North American CO2 fluxes. Optimized CO2 fluxes are then combined with plant discrimination to create isofluxes, which are optimized simultaneously with terrestrial disequilibrium fluxes. We are left with estimates of the isotopic signature of photosynthesis, terrestrial disequilibrium flux, and related error. Influence functions (i.e. influence of surface fluxes on measurements made “downwind”) are generated with FLEXPART, driven by National Centers for Environmental Prediction Global Forecast System meteorology. Prior isofluxes (CarbonTracker 2010 posterior net ecosystem exchange multiplied by biosphere 13C from SiB, and disequilibrium flux from CASA impulse-response functions and historical atmospheric CO2 observations) are of 3-hour, 1x1 degree resolution. Unoptimized fire and fossil fuel emissions are also from the CarbonTracker system, and background CO2 and 13C values are taken from NOAA/ESRL marine boundary layer and aircraft data. We invert for isofluxes using quasi-daily observations from tall towers in Park Falls, Wisconsin (WLEF). At this site the air is thought to be influenced predominately by corn production. Our aim is to disentangle the competing influences of agriculture, drought, and other climatic stressors on spatial and temporal variability in atmospheric 13C.

Nov. 10 Christina Sheldon, INSTAAR.
"Deglacial history and paleoceanography of the Umanak System, West Greenland "

The Greenland Ice Sheet (GIS) is the last remaining Northern Hemisphere ice sheet and arguably the most important archive of Late Quaternary and Holocene Northern Hemisphere climate. A record of ice-sheet and ice-stream history, ice-sheet ocean interactions, and paleoclimate is preserved offshore of the GIS in the sediments of the Umanak fjord, shelf trough and trough mouth fan system of West Greenland. During cruise JR175 of the UK ship RRS James Clark Ross in 2009, sediment cores and geophysical data were collected from the Umanak System to document the glacial history of the area. SWATH bathymetry data show that the Greenland Ice Sheet extended to the shelf edge via an ice stream in the Umanak System of West Greenland during the Last Glacial Maximum (LGM). The objective of this study is to document the timing and rate of ice retreat, and the role of the West Greenland Current (WGC) in initiating or sustaining ice retreat. This talk presents preliminary analyses of a transect of 4 cores from the upper slope to the inner Umanak shelf trough collected during JR175. Preliminary evidence will be presented for changes in environmental conditions as the core sites transitioned from subglacial to ice-proximal to open water from the LGM through the Holocene. With the knowledge that warm Atlantic Water impinging on the marine margins of the present-day GIS is speeding ice sheet retreat, this project is investigating the past interactions between the Umanak Ice Stream and the WGC through analysis of foraminiferal assemblages and stable isotopes on foraminifera.

Nov. 03 Darren Larsen, INSTAAR.
"Muddy Waters and the Arctic Blues: Reconstructing climate and glaciers from Icelandic lake sediments"

Iceland is totally extreme. Shaped by volcanism and molded by glacier ice, the island
is an active geological wonderland that uniquely marries tectonic and geomorphologic
processes in an arena the size of Colorado (~103,000 km2). Positioned in a region of
strong thermal gradients, Iceland is the largest landmass in the central North Atlantic
and is well situated to monitor Holocene climate variability and associated changes
in ocean and atmospheric circulation. Terrestrial climate there has been reconstructed
from a variety of geologic sources but remains coarsely resolved and/or incomplete. In
particular, information on past glacier activity is fragmentary and primarily relies on
dated moraine complexes, which are inherently limited and temporally discontinuous.
Temperate glaciers presently cover ~10% of the island and are sensitive to climate
variability, yet little is known about their evolution through the Holocene. This talk will
focus on recent work aimed at unraveling the Holocene climate and glacier evolution of
the central Iceland highlands. Laminated sediments from the proglacial lake Hvítárvatn
provide a continuous record of environmental change and the development of the
adjacent Langjökull ice cap for the past ~10.2 ka. Multiple glacier and environmental
proxies are placed in a secure geochronology with annual to multi-decadal resolution, and
reveal a dynamic Holocene terrestrial climate, characterized by non-linear behavior and
high magnitude changes. Emphasis will be placed on the behavior of Langjökull outlet
glaciers during the Little Ice Age, when most Icelandic glaciers attained their maximum
Holocene extent. Photographs of the central highlands, taken over multiple field seasons,
will be included to keep things interesting for all.

Oct. 27 Leif Anderson, INSTAAR.
"Contributions of sub-debris melt and ice face retreat to the rapid deflation of the debris-covered Kennicott Glacier Terminus, Wrangell Mountains, Alaska"

Debris covered glaciers are common in tectonically active or highly erodible ranges such as the Himalaya, Tien Shan, Alps, Southern Alps, and the Wrangell Mountains. Debris cover has a variable effect on the mass balance profile depending on its thermal conductivity, albedo, and thickness. Although debris cover generally reduces melt, melt within debris covered zones is complicated by the presence of bare ice faces which retreat at high rates relative to melt beneath debris. As the need to extrapolate individual glacier mass balance into regional trends grows under a changing climate and rising sea level, it is imperative that we develop a full understanding of the factors that alter glacier mass balance, in this case: debris-cover and ice face retreat.

In order to understand the influence of debris-cover on the retreat and deflation of glaciers, we completed a field campaign on the 43km long Kennicott Glacier in south-central Alaska from June to mid-August 2011. This valley glacier supports a 26kmsup2/sup debris-covered terminus with a high concentration of exposed ice faces relative to other debris covered glaciers. The debris covered zone exhibits extensive thermokarst and the distribution of ice cliffs is influenced by the presence of large sinuous supraglacial streams. Previous laser altimetry research on Kennicott glacier reveals that surface elevations have decreased in the debris-covered terminus at a rate of 0.34m/yr (1957-2000), and Precipitation-Temperature Area Altitude modeling shows monotonic ice loss from 1957-2008. Rapid deflation in the debris-covered terminus is likely the result of reduced ice advection from up glacier or increased melt in the debris-covered portion of the glacier over the last half century.

As a first step to understanding this rapid surface elevation reduction, we document melt beneath debris of variable thickness at 60 locations using ablation stakes, the horizontal retreat of 62 ice faces, and debris depth and surface temperature at 200 sites in the debris covered zone. We collected air temperature at three locations and temperature profiles through the debris at eight locations. We will document the orientation and concentration of ice faces using IKONOS imagery and then use a positive degree melt method with these temperature measurements to determine the contributions of melt beneath debris and ice face retreat to the total melt at the terminus.

Debris surface temperature data will be used to validate 30m resolution Landsat infrared data for the Kennicott Glacier and provide a necessary check on the infrared imagery often used in debris-covered glacier research. Thermal conductivity, derived from our profiles of temperature through the debris, in conjunction with our debris thickness data will be used to model the melt produced under the debris covered terminus of the glacier and be compared to our empirical results.

In further research, we will employ the feature tracking method to reveal spatial and temporal changes in advection and its effect on the elevation and extent of the debris-covered terminus of the Kennicott Glacier.

Oct. 13 Chris Florian, INSTAAR.
"A lake sediment record of Arctic Holocene climate using a multi-proxy study of
aquatic primary productivity"

Lake sediment core records are useful in the reconstruction of long-term regional climate. In arctic environments, lacustrine primary productivity is largely controlled by climate through alteration of the duration of ice-free conditions. In warmer times with longer ice-free seasons, total aquatic productivity is increased and species such as green algae and higher plants are more abundant. In colder times, diatoms predominate because their ability to bloom in early summer leaves them less impacted by the shortened growing season. Through the measurement of multiple productivity proxies such as carbon and nitrogen concentrations as well as stable isotopes, algal pigments and diatom species assemblages, a detailed understanding can be gained of the species shifts and changes in the total magnitude of primary productivity throughout the record. This can then be applied to reconstructing the regional climate history. In Qivitu Highlands Lake, located on eastern central Baffin Island in the Canadian Arctic, these proxies are used to develop a record of the last 10,500 years. The early part of the record shows strong early Holocene warmth with neoglacial cooling beginning approximately 6000 years BP. The strongest climate event influencing the record in this region appears to be the Little Ice Age, where all proxies show major changes. Anthropogenic warming is seen in the most recent sediments. This site is particularly sensitive to changes in temperature due to its small size and shallow depth and should therefore accurately record rapid shifts in climate. As of now, the most promising part of this study is the ratio of the pigments lutein (green algae and higher plants) to diatoxanthin (diatoms and chrysophytes), which show that modern conditions have returned to a similar state as during the Holocene Thermal Maximum.

Oct. 06 Adrianne Kroepsch, INSTAAR.
"The curious incident of the well in the Raton: An environmental investigation of alleged hydraulic fracturing impacts"

The present disagreements over natural gas development (namely, the use of hydraulic fracturing, or “frac’ing,” as an extraction mechanism) in the United States and abroad are currently being dubbed the next environmental “superdebate” – on par at least with contention over acid rain in earlier decades and at most with altercations over climate change in more recent years (Byrne, 2011). Natural gas development is controversial for many reasons; chief among them is the potential harm done to groundwater systems in the course of gas extraction by way of aquifer drawdown or contamination (EPA, 2011). While the national media’s focus on the Marcellus Shale might suggest that this controversy over groundwater quality is limited to the Northeast, residents of Colorado’s gas patches know that a large part of the story has been unfolding here for many years, in places like Weld, Garfield, and Las Animas counties. In this talk, I will present a recent case from the forefront of Colorado’s “frac’ing” debate. It is the case of a landowner’s domestic well in the Raton Basin, which became unusable due to sudden turbidity in the hours following the hydraulic fracturing of a nearby gas well (COGCC, 2011). In this interactive INSTAAR grad talk, we will collectively put on the cap of a state official responding to the complaint and work through the actual environmental investigation step- by-step. The real-life verdict will be concealed until the end of the experiment and a tally of interpretations will be taken – by the end of the discussion, how many will agree with the state’s final call on the data, and how many will disagree? At the very least, the exercise should serve as a reminder of the complexity of the groundwater systems many of us rely on and the uncertainty involved in understanding their behavior.

Byrne, D. (2011). Fracking and the road to energy independence. Chicago Tribune.

Colorado Oil and Gas Commission. (2011). Report of Commission and Order, Order No. 1V-363, Docket No. 1102-OV-04.

U.S. Environmental Protection Agency. (2011). Draft Plan to Study the Potential Impacts of Hydraulic Fracturing on Drinking Water Resources. Washington, D.C.: U.S. Environmental Protection Agency.

Sep. 29 Stephanie Higgins, INSTAAR.
"Sinking river deltas: remote sensing of subsidence and topography"

Many of the world's largest river deltas are sinking. Despite decades of research, it is still unclear whether the sinking is natural (caused by sediment compaction and regional tectonics) or man-made (caused by oil extraction and choked sediment supplies). Current techniques for mapping and understanding delta subsidence are not conclusive, because they rely on arrays of devices (GPS or tide gauges) to obtain a few measurements across huge areas. In the last fifteen years, however, Interferometric Synthetic Aperture Radar (InSAR) has emerged as a technique that can produce subsidence maps with much higher spatial resolution than any array-based method. InSAR uses satellite radar data to measure height changes of the earth’s surface. It has a spatial resolution of 20 meters in the horizontal, and up to 5 mm in the vertical, allowing it to map subsidence across deltas in great detail. InSAR can also be used to create topographic maps that penetrate vegetation canopies, so that low-lying topography of vegetated coastlines can be resolved and evaluated for flood risk. This talk will discuss the principles of InSAR, and evaluate InSAR's potential for improving our understanding of delta topography and subsidence.

Sep. 22 Matthias Vanmaerck, INSTAAR.
"Catchment sediment yields are not what they used to be … But what has changed?"

In this talk, I would like to present and discuss the findings of my ongoing PhD-research. It is well known that deforestation and agriculture can significantly increase erosion rates at the hillslope scale. Human impacts on sediment yield at the catchment scale (SY, t km-2 y-1) are , however, less well understood. An important issue that impedes this understanding is our inability to quantify the SY from a catchment before it was affected by human impacts, i.e. the Pre-Anthropocene SY.

To address this research gap, an extensive database of measured SY-data for around 2,000 catchments of various sizes in Europe was established. Based on a selection of these data, consisting of measured SY-data from catchments that are not or little affected by humans, a simple model was developed that allows to estimate the Pre-Antropocene SY of a catchment, based on its topographical and lithological characteristics and its sensitivity to earthquakes. Hence, this model can be applied to currently disturbed catchments, allowing a comparison between the pre-antropocene and

actual SY. In this way, we hope to increase our understanding about the human impact on SY at the catchment scale.

Sep. 15 Andy Wickert, INSTAAR.
"North American topographic and drainage evolution since the Last Glacial Maximum driven by ice sheet - solid earth interactions"

The solid Earth, fluvial system, and climate have been in an interconnected state of change through the last glacial cycle. In North America at the last glacial maximum, ice masses covered much of the continent; as a result of these continental-scale ice sheets, relative sea levels and surface topographies changed dramatically. Drainage basin boundaries moved in response to this changing paleogeography, altering the timing, amount, and location of water discharge to the oceans. I will discuss the components of a self-consistent theory of topographic and sea level change: eustasy, isostatic adjustment, geoid deflection, and true polar wander. These concepts will then be connected to paleogeographic and drainage reconstructions of North America from the last glacial maximum to present, with examples drawn from the Mississippi River and the Bering Strait. Much of our work in understanding the last glacial cycle involves modeling to interpret limited data, so I will also provide a brief introduction to the Community Surface Dynamics Modeling System, an NSF center based at INSTAAR to build a computer modeling framework for Earth surface processes.

Sep. 08 Teresa Legg, INSTAAR.
"Labile and redox-active organic matter sources influence bacterial community structure and groundwater arsenic mobilization."

Research throughout the last decade has generated a generally accepted model for groundwater arsenic (As) mobilization in South and Southeast Asia: labile organic carbon fuels the microbially-mediated reductive dissolution of iron (Fe) oxide minerals, which releases As sorbed to Fe oxides into the groundwater. Humic substances, redox reactive fraction of dissolved organic matter, are present in high- As groundwaters in the GBD (Mladenov, et al. 2010), and could play an important role in groundwater As mobilization (Jiang, et al. 2009; Jiang & Kappler 2008). Recent research at our field site in Araihazar, Bangladesh suggests that natural organic matter in the high- As aquifer contains both labile components and humic substances capable of enhancing Fe-reduction through abiotic or microbially-mediated electron-shuttling (Mladenov et al., 2010). Thus we set out to investigate how different carbon sources influence bacterial community structure and groundwater As mobilization by conducting a sediment incubation experiment. We incubated the sediment and groundwater for 80 days under different treatment conditions: 2 mM acetate (labile carbon); 5 mM AQDS (a redox-active carbon compound); 2 mM acetate and 5 mM AQDS; native humic substances, redox-active components of the DOM; and no addition/control. We found significant (p0.001) shifts in bacterial community structure, as measured by the UniFrac metric (Lozupone & Knight 2005), from the pre-incubation conditions to the post-incubation conditions. In addition, the different treatments induced significant differences in the structure of the bacterial community (p0.001). Also, the relative abundance of Deltaprotebacteria was significantly higher in the incubations amended with 2 mM acetate and 5 mM AQDS than those amended with only 2 mM acetate, only 5 mM AQDS, only native humic substances or groundwater (control). Interestingly, groundwater Fe and As mobilization was also significantly higher in the incubations amended with 2 mM acetate and 5 mM AQDS (p ≤ 0.002). Thus, these results suggest that native Deltaproteobacteria within the aquifer sediment are able to pair the oxidation of labile carbon to the reduction of redox- active, HS-like carbon sources to accelerate Fe- and As- mobilization.

Sep. 01 Ryan Vachon, INSTAAR and Earth Initiatives.
"Science Outreach: calculated approaches to celebrating the act of discovery."

Science Outreach, broader impacts, communications are essential components to most research proposals. There is a widespread recognition that the public could greatly gain from understanding the incredible science that we conduct. There are numerous ways to convey scientific information (school visits to videos, websites to teacher trainings) and just as many sorts of individuals to reach (children to science peers, parents to political opponents). Earth Initiatives, an affiliate of INSTAAR, is a non-profit organization that strives to use its skill sets to communicate scientific concepts to the public and other researchers in manners appropriate for the intended audience. During the graduate student talk, Ryan Vachon will talk about several of the initiatives taking root under the organization and in association with INSTAAR. Additionally, a number of concepts are in development, and the best way to move them forward is to brainstorm with you folks. New ideas are welcome.

Aug. 25 Will Wieder, INSTAAR.
"Tropical forests, methane flares, & undergraduate research at INSTAAR."

As a leader in environmental science research, CU students interested in conducting undergraduate research have access to a wealth of resources and opportunities. Many of us at INSTAAR mentor undergraduate students, but I would like to share information about a new program that pairs early career ENVS work-study students with research labs at INSTAAR. To maximize gains from undergraduate research opportunities for both mentors and mentees, this program also offers participating students training and support which compliments the activities of the host lab. Come learn more about how you can mentor an undergraduate in your lab and hear about the exciting independent work of Hana Fancher, who is working with members of the Townsend Lab on methane production from oil palm effluent settling ponds in Costa Rica.

Spring 2011

Apr. 28 Katie Hayo, INSTAAR.
"Reconstructing sea-surface temperature with alkenones."

The Norwegian Sea is the primary conduit through which warm Atlantic water reaches the Arctic Ocean. As such is has strong implications for both the recently observed Arctic warming and regional biological productivity making it an important location for climate monitoring. This study uses alkenones to reconstruct SST and primary productivity variability within the Norwegian Sea over the past 550 years. Results show a decoupling of phytoplankton vs. zooplankton derived SST reconstructions, confirming the observations of previous studies within the basin. Our results suggest differences in depth habitat and water column structure as the most likely cause of observed differences. Additionally strong inverse relationship was found between primary productivity and changes in solar intensity, suggesting an atypical control over bloom size in the region.

Apr. 14 Morgan Zeliff, INSTAAR.
"Tracing snowpack meltwater: oxygen-18 holds secrets of hydrologic connectivity in the high alpine, Colorado Front Range."

Stable isotopes and hydrochemical constituents of water were used to evaluate the role of groundwater in two high-elevation, snowmelt dominated areas of the Colorado Front Range: The 8-ha Martinelli catchment at 3,440 m and the nearby Saddle site at 3,530 m. The Martinelli site has three shallow (1.5 m) and 3 deep (> 6 m) piezometers, while the Saddle site has 4 sets of deep and shallow piezometers. All wells were screened for their bottom 1.5 m. All shallow piezometers had water only during snowmelt. In contrast, all deep piezometers had water year-round, with water depths generally deeper than 4 m during the winter and water rising to the surface during snowmelt, followed by a long recession limb. Starting in 2006, water samples were collected weekly to monthly from all piezometers, and for precipitation, snow, and surface water and analyzed for stable isotopes and major solute chemistry. The snowpack had a mean δ18O value of -20.43 ‰ (n = 52), ranging from -22 ‰ to -18 ‰ during snowmelt. The 4 per mil difference in δ18O during snowmelt was from fractionation of meltwater as it infiltrated through the snowpack. The mean δ18O value of -19.14 ‰ (n =299) for the piezometers at the Martinelli site did not differ significantly between shallow and deep piezometers (p = 0.1684), nor between the piezometers and either the snowpack or stream. In contrast, shallow and deep piezometers at the Saddle site were significantly more enriched than Martinelli with a mean δ18O value of -16.95 ‰ (p < 0.001, n = 417). A plot of the δ18O versus δD values from all wells along with the Global Meteoric Water Line (GMWL) provides evidence of depletion of these isotopes in the well waters. Mean calcium concentrations at the Martinelli piezometers (89 μeq L-1) were more than an order of magnitude more dilute when compared to mean values from the Saddle piezometers (1684 μeq L-1). Mean silicon concentrations are also significantly (p<0.001) more dilute at the Martinelli piezometers (62 μeq L-1) than mean concentrations from the Saddle piezometers (200 μeq L-1). These results, combined with hydrogeological information, suggest that the Martinelli catchment is an unconfined aquifer with direct hydrologic connection between surface waters and groundwaters and has a groundwater system dominated by direct snowmelt recharge. In contrast, groundwater at the Saddle site appears to be in a confined aquifer with a relatively long residence time and with no direct connection between piezometers and overlying snowmelt.

Apr. 07 Whitney Doss, INSTAAR.
"New insights into glacial deep ocean circulation and carbon storage: A multi-proxy approach using benthic foraminiferal elemental ratios."

Paleoatmospheric measurements generated from Antarctic ice cores have revealed the intriguing and oft-cited correlation between levels of carbon dioxide and air temperature over the past 800,000 years. This has sparked considerable debate over the extent of the role of this greenhouse gas in controlling or amplifying the glacial-interglacial transitions. Since the Vostok measurements only provide a “snapshot” of past climatic conditions and don’t reveal causal mechanisms, more data is required to understand natural carbon cycle variability in the past. The deep ocean is widely recognized to have been the repository of excess carbon during glacial episodes, accounting for the observed ~90 ppm drawdown of atmospheric pCO2. So how might ocean biogeochemical processes have naturally changed such that the ocean became an even larger carbon “sink”? One way to increase the surface ocean’s uptake capacity for atmospheric CO2 is to shift the speciation of the dissolved inorganic carbon pool in seawater away from aqueous CO2 and towards the carbonate ion (CO32-). Very simply put, we may consider average ocean CO32- concentrations and atmospheric pCO2 to be inversely related.

My research investigates the link between the marine carbonate system and atmospheric CO2 during the last glacial cycle. It is hypothesized that changes in the carbonate system reflective of increased deep ocean carbon storage will be recorded in deep ocean [CO32-]. The boron content of the calcite tests of bottom dwelling, single-celled protists called benthic foraminifera has been shown to reliably record deep water ΔCO32- with respect to calcite (ΔCO32- = [CO32-]in situ – [CO32-]saturation) over glacial-interglacial timescales. In other words, benthic foraminiferal B/Ca allows us to investigate the timing and magnitude of CO2 rearrangement to the extent that it was represented at the location of a particular deep ocean sedimentary core. I will present my preliminary B/Ca records from 3 cores spanning ~2.2 to 3.6 km water depth in the deep eastern equatorial Pacific. Additionally, I will introduce a recent approach to investigate both chemical and physical aspects of the glacial ocean using a full suite of benthic foraminiferal trace metal measurements. This “multi-proxy” method utilizes measured concentrations of boron (B), magnesium (Mg), cadmium (Cd), and zinc (Zn) as proxies for ΔCO32-, bottom water temperature, labile nutrient status, and refractory nutrient status, respectively.

Mar. 31 Jessica Weinkle, Center for Science and Technology Policy Research.
"Hurricane Insurability: What is the problem?"

Since the mid 90's, claims have run ramped that changes in hurricanes have led to increased damage costs. While most play lip service to the socioeconomic basis for such rising costs, homeowners insurance premiums have also risen. Today, there are claims that climate change has led to a "crisis" of insurance availability and affordability. In Thursday's talk I will introduce the public policy debate as it stands in Florida and ask if the problem is one of looming climate change, evil insurance companies, or poorly constructed state regulations.

Mar. 10 Brie Van Dam, INSTAAR.
"Atmosphere-snowpack ozone exchanges in the Arctic: an overview of methods, initial results and significance."

The snowpack is an active photochemical environment, driving important chemical interactions at the snow-atmosphere interface. With changes occurring both in the amount of pollutants transported to the Arctic, as well as changing amount and physical properties of the snowpack, significant effects in chemical budgets in the Arctic troposphere are possible. This indicates a need to understand the current dependencies of ozone exchange at the snow surface; yet despite this need, measurements of ozone deposition velocities reported in the literature are highly variable, and the processes impacting ozone behavior within and above the snowpack are not well understood. In order to address these concerns, a study with continuous, year-round measurements of ozone exchanges between the atmosphere and snowpack was implemented at Summit, Greenland between June 2008 and July 2010. Another campaign began at Toolik Field Station in northern Alaska in September 2010 and will continue through this winter and spring season. These measurements consist of a variety of observations used to investigate gas exchanges by implementing multiple techniques such as eddy covariance fluxes and gradient derived methods. Year round measurements at multiple sites in the Arctic and other snow covered regions will greatly improve our description of the processes controlling the exchange of ozone over polar snow, and how this will ultimately have an impact on the tropospheric ozone budge

Mar. 03 Rachel Gabor, INSTAAR.
"Using fluorescence spectroscopy and PARAFAC analysis to characterize the water-soluble organic matter in a first order alpine catchment

The increasing concentrations of dissolved organic matter observed in many northern latitude regions1 have potentially significant effects on both ecosystem dynamics and water treatment processes. Many hypotheses for the cause of this change in aquatic concentrations are dependent on changes in catchment processes2. Thus, to better understand the dynamics of dissolved organic matter, it is important to elucidate the connection between soluble organic matter in soil and dissolved organic matter in associated streams, with a particular focus on the chemical character of each organic matter pool. In this study, fluorescence spectroscopy has been used to characterize the water-soluble organic matter in the soil of a first-order catchment within the Boulder Creek watershed. Soil samples were collected with an aim to identifying both spatial and temporal patterns in the soil, as well as comparing extraction techniques. Little variation was found temporally, however, there was a noticeable difference in DOM quality between north- and south-facing slopes and the riparian zone. The moister, more vegetated, north-facing slope has a more advanced weathering profile and longer-lived snowpack, and the organic matter had a younger, more microbially-dominated signal with more reduced character compared to the south-facing slope. By placing these signals into the scope of the larger watershed and comparing them to correlated aquatic samples, it should be possible to develop a clearer picture of the role of terrestrial inputs to dissolved organic matter dynamics and how first order catchments influence larger watersheds.

Feb. 24 Keith Musselman, Civil Engineering, UCLA.
"The use of detailed forest structure to explain plot scale snowmelt patterns in a conifer forest: improving physically based model representation of sub-canopy hydrometeorology. Results from a southern Sierra Nevada CZO, Sequoia National Park, CA."

We present the use of detailed canopy structure as measured by hemispherical photographs taken at locations coinciding with 24 ultrasonic snow depth sensors, coupled with above canopy radiation measurements, to estimate sub-canopy solar irradiance. We relate both the detailed canopy structure and simulated direct beam fluxes to three years of measured sub-canopy snow dynamics recorded by the automated depth sensors and repeated density measurements (i.e. SWE ablation indicators) along a sub-alpine elevation gradient. The relationships observed at the scale of our forested research plots serve to inform optimal treatment of canopy structure in physically based snow models as well as to guide the use of increasingly available LiDAR data for basin level hydrological applications. To improve understanding of the feedbacks between atmospheric processes, forest canopy structure and the spatiotemporal evolution of snow properties and soil moisture, we apply a one-dimensional snow, vegetation and soil model (SNOWPACK) with a modified treatment of high resolution canopy transmissivity. The results of this work may be used to inform the development of improved forest cover parameterizations necessary for regional climate models, macro-scale hydrologic models, and ecosys

tem models.

Feb. 17 Ursula Quillman, INSTAAR.
"The 8.2 ka event on the NW Iceland Shelf as recorded in paired d18O and Mg/Ca measurements of the benthic foraminifer Cibicides lobatulus."

The 8.2 ka event was a short-lived climate excursion that holds important information about causes of abrupt climate changes during the otherwise climatically stable Holocene epoch. The 8.2 ka event was first documented in Greenland’s ice core records as a sudden drop surface air temperatures, ranging from 3 to 8°C degrees, depending on various reconstructions. The cooling has been attributed to the catastrophic drainage the proglacial lakes Agassiz and Ojibway during the final deglaciation of the Laurentide ice sheet into the North Atlantic Unequivocal proof that freshwater from theses proglacial lakes triggered the 8.2 ka event climate excursion is lacking. And there is limited knowledge of how the 8.2 ka event is expressed in the ocean - in timing, in duration, and in rates of temperature and salinity changes - because open ocean sedimentation rates are generally low and thus provide poor temporal resolution compared to the highly resolved Greenland ice core records.

We aimed to determine the timing of the onset and termination of the 8.2 ka event, the evolution and magnitude of temperature change, and whether the cooling was accompanied by a freshening in the marine realm by sediment core MD99-2266 from the mouth of Ìsafjarðardjúp, the largest fjord in NW Iceland. MD99-2266 contains 38 m of Holocene sediment. We concentrated the analysis on the interval from 8400 to 7600 cal yr BP that likely captured the 8.2 ka event signal. The chronology for MD99-2266 is based on 20 radiocarbon dates and the depth of the Saksunarvatn tephra. The interval from 7600 to 8400 cal years BP is bracketed by dates at 1398-1399 cm (7315±75 cal yr BP, 6390±20 14C years) and at 2237-2238 cm (8816±85 cal yr BP, 7885±15 14C yr); three additional dates lie within this interval. The high sedimentation rates in our record allowed us to subsample every 10 cm at an ~18-year resolution. We reconstructed temperature by measuring Mg/Ca of Cibicides lobatulus, a benthic foraminifer. To convert the Mg/Ca ratios to temperatures, we developed a new Mg/Ca temperature calibration for C. lobatulus based on 26 surface sediment samples and core tops from 16 locations in the high latitude North Atlantic.

We reconstructed the oxygen isotopic composition of seawater (d18Osw) to detect any freshening signal by taking the Mg/Ca derived temperatures to separate the d18Osw contribution from the oxygen isotopic composition of C. lobatulus (d18Ocalcite) in the same samples. All of our proxies indicate a prominent climate excursion, coinciding with the 8.2 ka event as registered in the GISP2 ice core record. Mg/Ca derived temperatures showed a cooling of ~2.7-4°C between ~8300 and 8170 cal yr BP accompanied by lighter d18Osw values of ~0.6-1.1‰ between ~8260 and 8220 cal yr BP. The percentages of the arctic species, Cassidulina reniforme, spiked from a mean of 5% to a high of 11% at ~8235 and 8240 cal yr BP; the percentages of the arctic species, Elphidium excavatum f. clavata, spiked from a mean of 4% to a high of 15% at ~8240 cal yr BP. Carbonate weight percent, a proxy for bioproductivity on the Icelandic shelf dropped during the cold event. The interval of low CaCO3 started at ~8260 cal yr BP with a drop from ~ 16% to ~10%; the lowest CaCO3 of 9.6 % occurred at 8240 cal yr BP. The interval of low CaCO3 ended at ~8220 cal yr BP. The 8.2 ka event lasted ~170 years with a 40-year peak cooling interval in our record, thus matching the 8.2 ka event as recorded in Greenland ice core records.

Feb. 10 Shelly Sommer, INSTAAR.
"Cite it right: Demonstration of EndNote Web, with a side of Zotero."

Using EndNote Web or another web-based tool for managing your citations will save you months of time over the course of your career. INSTAAR librarian Shelly will demonstrate how to sign up for an EndNote Web account; how to collect, organize, and format citations; and how to use Cite While You Write in your Word documents. We will also look briefly at similar tools (EndNote, Papers, RefWorks, and Zotero).

Feb. 03 Tyler Jones, INSTAAR.
" My summer glaciology course in McCarthy, Alaska."

The 1st International Summer School in Glaciology was held during June 2010 in McCarthy, Alaska at the Wrangell Mountain Center. McCarthy is located roughly 8 hours drive south of Fairbanks in south central Alaska. McCarthy is a small village (the population was 42 in the last census) in immediate vicinity to 5000 sq km of glaciers originating in the Wrangell Mountains, part of the Wrangell – St. Elias National Park (the largest in the US).

The course offered students, myself included, a comprehensive overview of the physics of glaciers and current research frontiers in glaciology. I will give an overview of my experience in McCarthy, relate some fun facts about this unbelievable town, and summarize some of the current ongoing research as best I can. Come learn a little bit about glacial lake outburst floods, ice penetrating radar, laser altimetry, sea level rise, and whatever else I can remember! I'll also mention the history of copper mining at Kennecott (the richest known concentration of copper in the world), why there is no road to McCarthy (nobody wants one) and how it felt to be a vegetarian for three weeks (pretty darn good).

Jan. 20 Ryan Vachon, INSTAAR.
"Accessing "Swing Thinkers": Communicating Climate Science to the Frustrated and Confused (film included)."

Conveying scientific information is often beleaguered by disengaged minds. Confusion, frustration, intimidation by sheer volumes of information and a feeling of powerlessness result in paralysis. Climate science is a perfect example. However, in truth, disenfranchised individuals are deep wells of latent motivation and vigor that can power much creative thinking, and action in schools, communities and government circles. Similar to the huge potential energy that politicians seek to woo of swing voters, science-numbed people, “swing thinkers”, can be engaged and activated. What does it take? Transformation. With an emotional and intellectual conversion, internalization of information begins. In turn, this knowledge powers innovation and wise decision-making.

The road to activating swing thinkers is not easy. Through examination of practical experiences and consultation with communications and mediation specialists, a pedagogy has been developed to lubricate the cogs of imagination, energize the frustrated and educate the swing thinkers. Indeed, how information is presented is a key factor to consider, however, there are preceding steps essential to get to the point where unimpeded information retention can occur. In this presentation we will present a paradigm for effectively engaging swing thinkers. We will illustrate this process, in part, with an adventure science film about high altitude ice coring.

Fall 2010

Dec. 02 Joey Knelman, INSTAAR.
"Plant-microbe interactions in deglaciated landscapes."

Deglaciation, increasingly an emblem of climate change, exposes new substrate and provides a natural chronosequence, a space for time substitution, with which to examine long-term ecosystem development within a single site. The relative simplicity of chronosequence biotic communities and nutrient dynamics has facilitated advances in ecological theory regarding soil development, shifts in plant functional groups, and species-species interactions. Given that all these phenomena are linked to belowground microbial communities, such sites provide unique opportunities to develop new microbial-based understandings of processes from biogeochemical cycling to plant community assembly. I will present research that evaluates feedbacks between plants and microbes by assessing shifts in bacterial community structure and function in coordination with plant colonization based on recent analysis of bacterial 16s ribosomal DNA sequencing from our study site at the Mendenhall Glacier in Juneau, AK. I will touch on ongoing work in plant-associated mycorrhizal and fungal endophyte communities in these environments.

Nov. 18 Jennifer Petrzelka, INSTAAR.
"The effects of a climate manipulation experiment on snow properties and snow surface energy balance, Niwot Ridge, Colorado."

It is widely accepted that global warming is occurring as a result of increasing greenhouse gases (IPPC, 2007). Changes in climatic variables alter snow properties such as snow depth, snow grain morphology, stratigraphy, and density. These characteristics play an important role in radiative fluxes through the snowpack. Understanding the energy budget of the snow surface is essential to providing information on a number of processes, such as snowpack ripening, snow metamorphism, snowmelt production and runoff, and biochemical cycling.

The consequences of a changing climate has created a desire among scientists to develop a methodology to simulate global warming in order to study the effects it may have on hydrological, ecological, and biological systems. A global warming experiment that uses infrared heaters to warm plots has been implemented on Niwot Ridge, Colorado since 2008, at three sites along an elevational gradient. An important aspect in interpreting these experiments, as well as developing a better understanding of interactions between climate, hydrology, and ecological processes is how the snowpack responds to radiative forcing caused by IR climate manipulation experiments.

Preliminary results from the 2009-2010 winter season illustrate significant differences in snowpack formation and snow properties between heated and control plots, as well as between all three sites. At the lower subalpine site, heated plots became snowfree 24-48hrs after every storm. At the upper subalpine site, melt occurred a week earlier in the heated plots, and the entire site became snowfree by June 11. On the contrary, the alpine site did not become snowfree until June 19, and heated plots varied in melt out date from 0-5 days earlier than control plots. Part of the explanation lies in the thermal regime of the snow. The formation of caves in the alpine and subalpine sites due to the uneven distribution of energy from the heaters altered the flow of heat causing different snowmelt characteristics.

Nov. 11 Ryan Daly, INSTAAR.
"An investigation into the seasonality of biogenic volatile organic compound emissions."

Vegetation naturally emit a variety of highly reactive hydrocarbon compounds, classified as biogenic volatile organic compounds (BVOC), which are known to have large implications on atmospheric chemistry. Once released into the troposhpere, BVOC participate in reactive nitrogen, hydroxyl and ozone chemistry as well as secondary organic aerosol formation. The resulting air quality impacts warrant a thorough understanding of BVOC emission behavior, critical for effective regional modeling and legislative decision-making. This work aims to improve the database and algorithms used in biogenic emission models by examining the seasonal trends of two classes of BVOC, monoterpene (MT) and sesquiterpene (SQT) hydrocarbons. A field site established at a local tree nursery provided an opportunity to easily monitor the emissions of naturally growing vegetation throughout a growing season. The emission rates of five tree species native to Colorado forests were measured monthly between February 2009 and February 2010. Emissions were found to exhibit seasonal patterns with higher rates observed between spring and late summer, falling to a low through winter months. However, seasonal trends prove to be very complex with drastic variation in seasonal shape and strength for different vegetation species. These findings are discussed and call into question the methods used for calculating normalized emission rates used by atmospheric models.

Nov. 04 Lee Stanish, INSTAAR.
"The diversity and biogeography of microbial communities in Antarctic Streams: Cyanos rule!"

The McMurdo Dry Valleys of Antarctica are among the coldest and driest ecosystems on the planet. Microbial life dominates, particularly in the glacial melt water streams that flow during the austral summers. In such a water-limited environment, Dry Valley streams are hotspots of biological activity. In streams with suitable physical and hydrologic characteristics, thick microbial mats can develop and attain high biomass. Microscopic observations demonstrate that these mats are dominated by photosynthetic microbes, although these mats are known to be important sites for nutrient cycling and therefore must support more functionally diverse organisms. The goal of this project is to characterize the bacterial diversity in dry valley stream microbial mats and to determine the spatial variation in microbial communities across valleys. DNA was collected from microbial mats and 16S ribosomal RNA gene sequences were obtained using high-throughput pyrosequencing. This talk will present preliminary results on microbial community diversity across spatial and environmental gradients.

Oct. 28 Adriana Bailey, ATOC/CIRES.
"Using stable water isotopes to distinguish aerosol chemistry from transport."

Very often, changes in atmospheric constituents are strongly influenced by atmospheric transport and mixing processes, and it is difficult to separate out changes due to chemistry. Changes in particle number, size, and composition due to in situ nucleation and growth or evaporation may be difficult to differentiate from changes due strictly to advection. This can be especially problematic for Eulerian observation frameworks. The stable isotopic composition of water vapor is a powerful tracer of atmospheric mixing. During periods when distinct air masses exchange without undergoing condensation or evaporation, the inverse of total water vapor is linearly proportional to the δD value—the fraction of heavy-to-light vapor with respect to a reference standard. We present a new technique that exploits this relationship to account for the effect of mixing on observed changes in aerosol size distributions. We use simultaneous measurements of aerosols and vapor isotopologues, measured at the Mauna Loa Observatory with an Ultra-High Sensitivity Aerosol Spectrometer and a Picarro water vapor isotope analyzer. Using a two-member mixing model, the mixing exchange coefficient is constrained by the water isotopologue information, allowing aerosol changes due to advection to be singled out. The production rate is thus explicitly solved for, even during periods when atmospheric transport clearly dominates.

Oct. 21 Ursula Quillman, INSTAAR.
"Holocene subpolar gyre evolution and implications for paleonutrient transport to high latitudes."

Pronounced changes in the water mass properties of the northern North Atlantic have taken place over the last decades and substantial evidence is being provided over the past five years that the observed changes are caused by exchanges between polar water masses and subtropical water masses in the North Atlantic subpolar gyre (SPG). However, mechanisms and implications of SPG are not well understood. By looking at Holocene SPG evolution we can add to our understanding of ongoing and future changes in SPG dynamics.

We present the results of Mg/Ca and Cd/Ca ratios measured on Globigerina bulloides, a planktic foraminifer, from core NEAP4K from Björn Drift in the northern Iceland Basin south of Iceland (61° 29.91 N, 24° 10.33 W, 1627 m water depth), which lies in a critical position to monitor fluctuations in the density and nutrient structure at the eastern SPG boundary. We calculate the temperature from the Mg/Ca ratios in G. bulloides and combine it with δ18Ocalcite to extract the δ18Osw contribution, which covaries with salinity in the upper oceans. Dissolved Cd has a similar distribution as the nutrient phosphate and therefore the Cd/Ca ratios are used as paleonutrient tracers.

We document regime shifts in the water mass characteristics at our study site at ~9.7, 7.7, 6.0, 3.8, 2.6. 1.9, and 0.9 kyr BP. The SPG went generally from more extended modes in the early Holocene to more contracted modes towards the present, except between 7.7 and 6.0, 2.6 and 1.9 and after 0.9 kyr BP when the SPG was extended again. During the extended modes the water masses showed more polar water characteristics and during the contracted modes more subtropical Atlantic water characteristics. Higher nutrient levels at the study site were present during extended SPG modes.

Oct. 07 Kurt Refsnider, INSTAAR.
"Reorganization of ice sheet flow patterns In Arctic Canada prior to the mid-Pleistocene transition."

The Foxe sector of the Laurentide Ice Sheet (LIS) experienced a complex and dynamic interplay between cold-based, non-erosive ice on uplands, fast-moving outlet glaciers that carved deep fiords through the Arctic Cordillera, and even more erosive ice streams that occupied larger straits and sounds, transporting ice from the Foxe Dome to calving margins in Baffin Bay and the Labrador Sea. The high topography of Baffin Island forms a broad barrier to the flow of ice to these calving margins and gradually has been dissected since the onset of Northern Hemisphere glaciation. However, evidence for the evolution of LIS erosion and basal thermal regime patterns during successive glaciations is poorly preserved in the geologic record. We use a new approach utilizing published till geochemistry and cosmogenic radionuclide (CRN) data to constrain the development of the fiorded coastline and the distribution of cold-based ice across central Baffin Island in both spatial and temporal domains over many glacial-interglacial cycles.

The combination of till geochemistry data, which is used to characterize till weathering, and modeled CRN burial-exposure histories provides strong evidence for a shift in basal thermal regimes across the interior plateaux of Baffin Island between 1.9 and 1.2 Ma. While it may be coincidence that this time interval abuts the onset of the mid-Pleistocene transition (MPT), it has been hypothesized that changes in subglacial conditions were potentially an important mechanism in altering LIS dynamics across the MPT. Prior to this time, ice was likely wet-based and erosive across the majority of the Baffin Island interior, but by 1.9-1.2 Ma, some parts of the landscape became perpetually covered by cold-based ice during glaciations, a pattern that persisted through the last glacial cycle. The modern fiord system also must have developed by this time, and preferential channeling of ice flow into major fiords may have been sufficient to effectively shut off ice flow across the landscape between outlet glaciers. These results imply that there was a major shift in the basal thermal regime across the northeastern LIS, and the subsequent expansion of cold-based ice and the concentration of ice flow in fewer outlet systems across this region may help explain the cause of the mid-Pleistocene transition from 41- to 100-kyr glacial cycles.

Sep. 30 Francesco Pausata, University of Bergen.
"Past climate variability: model analysis and proxy intercomparison."

By comparing model simulations and proxy data we provide new insights into atmospheric climate variability in the North Atlantic region during the late Quaternary (21 000 yr BP to present day). By analyzing a set of climate model simulations for the Last Glacial Maximum (LGM) and the Pre-industrial we describe the character of past atmospheric circulation variability and investigate the mechanisms behind it. Moreover, we analyze the impact of our findings on proxy records of past North Atlantic climate variability.

Further, by comparing proxy data with a model simulation of the Mid-Holocene we address the controversy regarding different temperature trends recorded by marine proxies in the North Atlantic Ocean.

Finally we tackle the impact of abrupt climate changes in the North Atlantic, such as Heinrich events, on Asian monsoon systems and on what in turn is actually recorded by cave deposits in southern and eastern Asia.

Sep. 23 Brian Seok, INSTAAR.
"What's causing morning nitric oxide 'pulse' above the canopy at a forested site in northern Michigan?"

Nitrogen oxides (NO + NO2 = NOx) and ozone (O3) concentrations below, in, and above the canopy were measured continuously during the summer and fall of 2008 from the Ameriflux tower at the University of Michigan Biological Station (UMBS). Temperature throughout the canopy and turbulent wind speed data above the canopy were also collected. The composite isopleths of the collected chemical vertical profile data show a rapid rate of increase in nitric oxide (NO) concentrations (Δ0.1 ppbv/hr) during sunrise (between 6 and 9 am EST) in the upper part of the canopy. There are several hypotheses to the source and cause of this observed morning NO concentration peak inside the canopy. One explanation could be upward transport of NO emitted by the soil to the crown-layer. An alternative hypothesis is that the source of the NO "pulse" in the morning is the result of photodissociation of nitrogen dioxide (NO2) accumulated overnight inside the canopy. In addition to interpreting the collected profile data, a single column canopy model is used to test these hypotheses and examine the combined effect of emissions, transport, chemistry, and deposition inside the forest canopy in modulating NOx and O3 atmosphere-biosphere exchange. Finally, I will reflect on how this research project is teaching me a valuable lesson in life and preparing myself for scientific career.

Sep. 16 Megan Bresnahan, Assistant Professor of Engineering Research and Instruction Librarian.
"Making the most of research resources in the sciences."

Participants will learn to effectively search library databases and other research tools for quality scientific literature and data. This workshop will focus on research strategies related to both scholarly databases, such as the Web of Science, and less traditional sources of information, such as Google Scholar. The speaker will also introduce attendees to Zotero, a free plug-in for the Firefox browser that allows users to quickly capture and cite references for a variety of sources, including journal articles, websites, blogs, and even photos Participants are asked to bring their laptops to this session.

Spring 2010

Apr. 29 Larry Bowlds, Managing editor of Arctic, Antarctic, and Alpine Research, INSTAAR.
"The parts of publishing a paper other than peer review."

Publishing a paper requires much more than a successful peer review. These steps include the following.

(1) Find the right journal for possible submission. Journals may have international or regional coverage. Journals may or may not have a Web presence. Journals may have a broad or narrow focus. The journal’s impact factor may determine its relative importance and its potential readership. Journals may or may not have page charges; these charges may be mandatory. There may be processing fees. Charges for color are usually mandatory for print, but smaller or free for online. Reprints almost always cost, but a PDF may be an economical alternative if available. The decision to choose a particular journal may also be affected by the journal’s frequency (is the journal monthly or quarterly). Before making a decision, ask the Editor about average review time, average time from acceptance to publication, and the journal’s backlog of unpublished manuscripts.

(2) Prepare the manuscript properly. Know the journal’s word-processing requirements. Know the journal’s style for citations, section headings, and references. Spell-check everything. Use the correct lettering size and font when drafting figures. Draft the figures as a set. If possible, draft the figures at publication size. Check the resolution of the figures by using the 400% rule. Do not draft in color if you plan to publish in grayscale unless the journal will post your color figures on the Web.

(3) After manuscript acceptance, maintain contact with the Editor. The Editor must know where you are at all times. The Editor must have a good e-mail address. Read everything word-for-word. Adhere to the Editor’s timelines. Finally, request a PDF of the final version of your paper.

Apr. 15 Bailey Simone, INSTAAR.
"Chemical characteristics of dissolved humic substances from arsenic-rich shallow groundwater in Bangladesh."

The release of dissolved arsenic into groundwater from geogenic arsenic bound to sediments is thought to be influenced by dissolved organic matter (DOM) through several biogeochemical processes. It has been shown that the DOM pool in a groundwater system in Bangladesh includes both reactive humic substances and labile substrates for microbial growth. Humic substances may promote the release of sediment bound arsenic through direct chemical processes, specifically the formation of humic-As complexes and competition between As and humics for sorption sites. Microbial degradation of the labile DOM substrates may enhance arsenic mobilization by creating reducing conditions with the ferric iron in the Fe-oxides of the sediments serving as the ultimate electron acceptor for microbial growth. Dissolved humics in the groundwater may enhance this process by acting as electron shuttles, and the additional release of sorbed humics by reductive dissolution of Fe-oxides may fuel a redox cascade. I will discuss the chemical characteristics of dissolved humics from groundwater, and surface water in an As-rich region in Bangladesh. Chemical characterization included fluorescence and carbon-13 nuclear magnetic resonance (13C-NMR) spectroscopy, elemental and lignin phenol content and 14C analysis. In general, the groundwater humics had characteristics similar to wetland fulvic acid, indicative being derived from plant and soil precursor materials. Whereas, the surface water humic sample had a characteristics showing a greater contribution of precursor material from microbial biomass. Taken together these results provide chemical evidence that microbially mediated reductive dissolution of Fe-oxides in As-rich groundwaters, releases both As and humics, which may in turn enhance electron shuttling capacity in the groundwater system.

Apr. 08 Phil Taylor, INSTAAR.
"Stoichiometric control of organic carbon-nitrate-phosphorous relationships from soils to sea."

Human creation of reactive nitrogen has risen an order of magnitude since the dawn of the Industrial Revolution. This dramatic reorganization of a global biogeochemical cycle has brought substantial benefits, but increasingly causes detrimental outcomes for both people and ecosystems. One such problem is the accumulation of nitrate and bioavailable phosphorus (P) in aquatic ecosystems. Here we establish that ecosystem nitrate and P accrual exhibits consistent and negative nonlinear correlations with organic carbon (C) availability along a hydrologic continuum from soils, through freshwaters and coastal margins, to the open ocean. Across this diversity of environments, we find evidence that resource stoichiometry (organic C:nitrate and organic C:P) strongly influences nitrate and P accumulation by regulating a suite of microbial processes which couple DOC and nutrient cycling. Collectively, these microbial processes express themselves on local to global scales by restricting the threshold ratios underlying nitrate and P accrual to a constrained stoichiometric window. Our findings help explain the fate of nitrate and P across disparate environments, which has significant implications for the management of a rapidly changing N cycle.

Apr. 01 Samantha Weintraub, INSTAAR.
"Estoy cansada, pero feliz: 7 weeks in the rainforest classroom of Costa Rica."

Due to its topography, climate, geology and location, the nation of Costa Rica, slightly smaller than the state of West Virginia, contains 4% of the globe’s biodiversity. This winter, I had the privilege to spend 7 weeks exploring the diverse ecosystems of Costa Rica. Hosted by the Organization for Tropical Studies (OTS), I participated in a graduate course designed to train young scientists in ecological research methods. While visiting dry forests, coastal zones, lowland wet forests and montane oak forests, we honed our skills in close observation while learning how to formulate and test biological hypotheses. We also investigated the effects of deforestation and land use change on forest function and ecology. The diversity of life forms we encountered was mirrored by the diversity of student and faculty participants, hailing from different regions and nations. The course was a wonderful collaborative experience. Come hear stories and see pictures of my exciting adventures in the neotropics!

Mar. 18 Adina Racoviteanu, INSTAAR.
"Himalayan glaciers: Integrating remote sensing, field methods and indigenous knowledge about climate change."

Anecdotal evidence from glacier termini observations in the Himalayas point to “alarming” rates of retreat in the past decades, and rapid formation of moraine-dammed lakes. Recent media reports present contradictory information on either “disappearing glaciers” or “healthy, stagnant glaciers”. Such statements are often supported by dispersed, limited information on glacier trends. Concomitantly, local communities in the Western Himalayas report changes in glacier extents, snow cover and weather patterns. In response to water scarcity, indigenous Himalayan cultures have begun a number of adaptive responses such as meltwater harvesting to construct “artificial” glaciers. Here I compare and contrast spatial patterns of glacier changes in the dry Western Indian Himalaya (Ladakh and Lahul-Spiti) with the wet, monsoon-influenced Eastern Himalaya (Khumbu and Sikkim). I will complement the scientific work with climate changes reported by local communities and recorded in video, oral testimonies and ground photography. This research is the result of field work conducted in India and Nepal over the past five years.

Mar. 11 Rachel Gabor, INSTAAR.
"Dissolved organic matter cycling in the Boulder Creek Watershed."

As part of the Boulder Creek Critical Zone Observatory, water samples were collected from several sites along Boulder Creek at regular time intervals beginning in May 2008. The concentration and quality of the Dissolved Organic Matter (DOM) in these samples was analyzed to understand the response to seasonal changes and variations in flow rates. Filtered samples were fractionated using XAD-8 resin and both whole water and fulvic acid fractions were analyzed for dissolved organic carbon concentration as well as with fluorescence and UV-VIS spectroscopy to determine its chemical character. In addition to stream measurements, surface soil samples along several transects were collected from Gordon Gulch as well as deeper samples from soil pits on both north-facing and south-facing slopes . DOM from these samples was leached with potassium sulfate and analyzed using the same techniques as the stream samples to compare the characteristics of the terrestrial organic matter available to be leached from the watershed with that of the DOM in the stream. While available soluble organic matter was significantly higher at the surface and tended to steadily decrease with depth, amount and chemical character did vary with soil horizon. These results were compared to the chemical signature of the DOM from the stream the catchment feeds. Organic matter from the surface was much more similar to the stream DOM than matter near bedrock

Mar. 04 Dylan Ward, INSTAAR.
"The use of ablation-dominated medial moraines as samplers for ¹⁰Be-derived erosion rates of glacier valley walls, Kichatna Mts., AK."

We use cosmogenic 10Be concentrations in amalgamated rock samples from active, ice-cored medial moraines to constrain glacial valley sidewall backwearing rates in the Kichatna Mountains, Alaska Range, Alaska. This dramatic landscape is carved into a small ~65 Ma granitic pluton about 100 km west of Denali, where kilometer-tall rock walls and “cathedral” spires tower over a radial array of over a dozen valley glaciers. These supraglacial landforms erode primarily by rockfall, but erosion rates are difficult to determine. We use cosmogenic 10Be to measure rockwall backwearing rates on timescales of 103–104 yr, with a straightforward sampling strategy that exploits ablation-dominated medial moraines.

A medial moraine and its associated englacial debris serve as a conveyor system, bringing supraglacial rockfall debris from accumulation-zone valley walls to the moraine crest in the ablation zone. We discuss quantitatively several factors that complicate interpretation of cosmogenic concentrations in this material, including the complex scaling of production rates in very steep terrain, the stochastic nature of the rockfall erosion process, the unmixed nature of the moraine sediment, and additional cosmogenic accumulation during transport of the sediment.

We sampled medial moraines on each of three glaciers of different sizes and topographic aspects. All three moraines are sourced in areas with identical rock and similar sidewall relief of ~1 km. Each sample was amalgamated from 25-35 clasts collected over a 1-km longitudinal transect of each moraine. Two of the glaciers yield similar 10Be concentrations (~1.6-2.2x104 at/g) and minimum sidewall slope-normal erosion rates (~0.5-0.7 mm/yr). The lowest 10Be concentrations (8x103 at/g) and the highest erosion rates (1.3 mm/yr) come from the largest glacier in the range with the lowest late-summer snowline. These rates are reasonable in an alpine glacial setting, and are much faster than long-term exhumation rates of the western Alaska Range as determined by thermochronometric studies.

Feb. 25 Whitney Doss, INSTAAR.
"RV Knorr Oceanographic Cruise 197-3: Demerara Rise 2010."

In a paper published in Paleoceanography (2005) entitiled “Glacial water mass geometry and the distribution of δ13C of ΣCO2 in the western Atlantic Ocean” Curry and Oppo used δ13C of benthic foraminifera to reconstruct glacial deepwater geometry in the western Atlantic. However, there remains little data from ~30S - ~25N at water depths shallower than 2km, which is needed to reconstruct the northward penetration of the glacial equivalent of Antarctic Intermediate Water. The main stated goal of this cruise located in the western tropical Atlantic was to collect cores to fill that gap. The cruise was a combination of surveying (3.5 kHz and swath bathymetry) to identify good coring locations, coring (multicore for surface sediment, gravity core for Holocene sediment, and long piston core for older sediment), and water collection (for 18O, C13, salinity, trace elements, and Nd isotopes.) We also collected large volume water samples for C14 at one station. In the ship’s lab, we collected multi-sensor track data on the gravity and long cores, and preformed some initial biostratigraphy that can be tied back to the MST data. Additionally, we slabbed multicore tops to preserve them for live benthic analyses and archived all the rest. During my talk I will present photos of the coring operations and labwork at sea, and further discuss the motivation, materials and methods employed on the RV Knorr. (And I will also explain why our cruise track looks like an Etch-A-Sketch).

Feb. 18 Rory Cowie, INSTAAR.
"Use of isotopic and geochemical tracers to identify source waters and subsurface residence times within headwater catchments in Boulder Creek Watershed, Colorado."

An outstanding question for snowmelt-dominated watersheds of the western US is the response of stream flow to changes in climate. We know little about mountain aquifers because they involve structurally complicated rocks, extreme head gradients, and dramatically fluctuating recharge due to seasonal snowmelt. In general, the western United States is predicted to face warmer temperatures and more frequent and prolonged droughts, and we can expect to see a decrease in annual snowpack, earlier onset of snowmelt, and increased evaporation. Understanding streamflow generation under these climatic conditions will become increasingly important as hydrologic inputs change drastically and outputs are increasingly needed for human consumption. To improve our understanding of surface/groundwater interactions, we are simultaneously collecting surface water, subsurface, and precipitation samples at four gauged headwater catchments along a 1,500-m elevational gradient: (1) Green Lakes Valley (3,500 m); (2) Como Creek (2,900 m); (3) Gordon Gulch (2,400 m); and Betasso (1,830 m). All water samples are analyzed for geochemical and isotopic (δ18O, δD) composition. The average residence time for subsurface flow is calculated by comparing the smoothing of the δ18O input (precipitation) and output (streamflow) using a convolution algorithm. The calculation of residence times is also constrained by measuring concentrations of tritium (3H), a naturally occurring radioisotope, to better understand sub-surface transit times. A two-component mixing model is used to determine source waters from old (reacted) waters and new (unreacted) waters. End member mixing analysis (EMMA) is a statistically unbiased technique that will also be used to identify the most important end members contributing to stream flow. The application of Principle Component Analysis (PCA) using the isotopic and geochemical measurements collected improves the accuracy of end member selection. Successful application of hydrograph separation and EMMA determines the proportions of sources contributing to stream flow and groundwater recharge. Additionally, the evolution of isotopic signatures (δ18O, δD) of snow will be analyzed through the transition from new precipitation to infiltration into the system during melt.

Feb. 11 Kate Zalzal, INSTAAR.
"Volcanoes in the Arctic System (VAST): Success, challenges, and future ."

Stratospheric aerosols from explosive volcanism can alter the radiative balance of the planet. Eruptions are increasingly considered a powerful forcing on climate variability and tephras (volcanic ash), from Quaternary Icelandic volcanism, are used to independently date sediments across the British Isles and northwest Europe. Volcanoes in the Arctic System (VAST), a collaborative NSF grant awarded in 2007, seeks to better understand the role of volcanism in the Arctic System and to optimize the utility of tephra layers deposited across the Arctic. Here I present the current status of the VAST project including the extraction of tephras from distal lacustrine archives on Ellesmere Island, Baffin Island and Svalbard, Norway. Geochemical fingerprinting via microprobe analysis of these tephras is necessary to identify a volcanic source and potential eruption date, however this remains challenging when dealing with extremely small (20-50 micron) tephra shards. In addition to plume trajectory, the distribution and abundance of tephras within marine cores on the Icelandic and east Greenland shelf, provides insight into modes of delivery (primary air fall, glacial outwash, sea ice transport) and the associated climatic and oceanic conditions. The VAST project also attempts to evaluate the sensitivity of the Arctic System to high- and low-latitude eruptions through climate modeling and comparisons of model output to paleoenvironmental reconstructions. Future work includes developing tephra stratigraphy from sites on Baffin Island and northwest Iceland and investigating land-cover response to eruptions.

Feb. 04 Kate Hayo, INSTAAR.
"Climate variability of the Medieval Climate Anomaly and Little Ice Age ."

Temperature and salinity for the last 2400 years were reconstructed from Mg/Ca ratios and oxygen isotopes from sediment cores from Chesapeake Bay (eastern US) to evaluate Medieval Climate Anomaly (MCA) and Little Ice Age (LIA) climate variability. Results show that MCA temperature maxima reached 16?C between 600 and 950 CE and LIA cooling began about 1000 CE reaching minima of ~8 to 9?C about 1150, 1350, and 1650-1800 CE. MCA warmth in the eastern US preceded the classic European Medieval Warm Period (950-1100 CE) and peak warming in the Nordic Seas (1000-1400 CE). In addition, the inception of LIA cooling was asynchronous across the North Atlantic. Precipitation variability in the eastern US included multiple dry intervals from 600 to 1200 CE, which contrasts with wet medieval conditions in the Caribbean. The eastern US experienced a wet LIA between 1650 and 1800 CE when the Caribbean was drier. These results suggest ocean-atmosphere processes influence MCA-LIA climate variability producing large regional temperature and precipitation anomalies.

Jan. 28 Shelly Sommer, INSTAAR.
"Navigating the information landscape: using library databases and tools effectively: Mad Search Skills and Library Database Smackdown."

Using library databases effectively makes life as a scientist a lot less painful. They are the maps to the information landscape. And maps are definitely needed to cope with the annual doubling of information produced, navigate rapid technological changes, and anticipate shifts in the distribution and character of information.

Shelly will lead a fast tour of the five library databases most useful to INSTAARs, focusing on when to use them and how to structure a good search. Bring a laptop if you like to follow along. By the time we’re done comparing and contrasting, you’ll know:
- When is Google Scholar enough, and when should I move to something else?
- Am I really finding everything?
- How do I get a good retrospective on a topic?

After that we’ll have a free-for-all discussion about library databases and tools, so bring your toughest/most fundamental/most oddball questions.

Fall 2009

Dec. 03 James Cullis,.
"Understanding the hydrologic factors affecting the growth of the nuisance diatom Didymosphenia geminata in rivers and the potential for using managed flood releases to control future growth."

Didymosphenia geminata is a nuisance diatom species impacting many mountain streams in Colorado and the western US. In recent years there has been an apparent increase in the tendency to bloom in traditional habitats as well as spreading to new watersheds. The most significant impact being the invasion of rivers in New Zealand where it has been identified as a threat to the sustainability of stream ecosystems. D. geminata appears to be more common in regulated streams downstream of reservoirs and lakes. One of the few controlling factors on growth is the physical removal due to elevated shear stress and bed disturbance. This has resulted in the consideration of managed flood releases from reservoirs as a potential mitigation measure. The objective of this research is to investigate the role of spatial and temporal variations in shear stress and potential bed disturbance in the removal of D. geminata based primarily on a number of study sites in Boulder Creek, CO. Initial results indicate that high flow events are significant in the removal of D. geminata and that a critical threshold may exist based on the non dimensional Shield's stress which is associated with the potential for bed disturbance. The results of the study will be useful in determining the magnitude, duration and timing of flood events necessary to control the growth of D. geminata which can then be considered along the the many other competing demands for water from reservoirs in the western US.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Selected Abstracts INSTAAR Grad Student Talks

Selected Abstracts
INSTAAR Grad Student Talks