GREENLAND

SHEAR MARGIN DYNAMICS: Observed increase in marine-terminating outlet glaciers over the Greenland Ice Sheet has been associated with warming. Regional variability in mass discharge from marine-terminating glaciers has been attributed to surface processes, local mass balance, and ocean-ice interactions at the terminus. This is a collaborative effort with Byron Parizek, Eric Larour, Helene Seroussi, and Mathieu Morlighem and Ken Jezek. Our group has sought to constrain the impact of surface processes on observed changes in outlet glacier thinning and speed-up through understanding the role direct surface melt water injection has on the shear margins of Jakobshavn Isbrae. We have identified spatially coherent, seasonally stable regions of water-filled crevasses along the shear margins, which drain each summer. We were the first to quantify the potential magnitude of melt water they can deliver to the bed and through the use of remote sensing, and modeling tools, we will further constrain the degree to which they have an impact on dynamics within the ice stream as well as outside through enhanced basal sliding or through cryo-hydrologic warming. This work is supported by NASA 

METEOROLOGICAL DRIVERS ON SURFACE MELT: This is a collaborative project with Dave Reusch and Chris Karmosky to diagnose spatio-temporal energy balance components responsible for the occurence and magnitude of surface melting over the Greenland Ice Sheet. My group is involved to develop, validate, and implement a multi-sensor fusion approach which involves the use of passive microwave data to characterize melt occurence. Once locations are identified as experiencing melt, these regions are decomposed into melt magnitude (skin liquid water fraction) through an analytical inversion through calibrating coupled optical and thermal signatures with a numerical snow/firn/ice melt model. Calibration is facilitated through the use of Artificial Neural Networks. This work is supported by NSF 

WEST GREENLAND GPS ICE DISPLACEMENT NETWORK: This is a collaborative project with Jay Zwally and Konrad Steffen. Over nearly the last two decades a collection of GPS recievers has been deployed on the ice sheet to monitor ice sheet motion in the ablation zone across the equilibrium line (ELA). My group is involved in managing the network and analyzing data to understand longitudinal relationships between changes in surface mass balance (melting, runoff, infiltration) and ice dynamic response. This work is partially supported by NASA 

SEASONAL FLUCTUATIONS IN BASAL LUBRICATION: This is a collaborative project with Ryan Walker. This efforts seeks to quantify seasonal variability in basal lubrication through inversion of summer and winter basal friction over the ablation zone of west Greenland Ice Sheet using the numerical ice sheet model ISSM.

SUPRAGLACIAL LAKES AND ALBEDO: This is a collaborative project with Thomas Mote. This work explores the impact of supraglacial lakes on regional ice sheet surface albedo. We establish that 10% of seasonal variability of summer-time albedo is attributed the collective impact of proliferated lakes in the ablation zone of the Greenland Ice Sheet.

ANTARCTICA

SUPRAGLACIAL HYDROLOGY: Increased surface melt rates along the margins of the Greeland Ice Sheet have accelerated meltwater production, consequently resulting in increased melt infiltration to the bedrock/ice interface. Infiltration is facilitated through drainage of surpaglacial lakes, through fractures and crevasses as well as moulins. Our aim to improve our understanding of the evolving supraglacial environment.

Our work has quantified the spatial clustering distribution of lakes and linked it to variability in melt production, drainage rates and other components of the supraglacial hydrology.

We also established the impact of subglacial topography on the distribution of lakes and quantified the relationships between lake distributions and ice flow dominated by internal deformation versus basal sliding.

EVOLUTION OF OF ANTARCTIC DRY VALLEY HYDROLOGY: This is a collaborative project with Michael Gooseff. The efforts seeks to understand changes in the Dry Valley's hydrologic system in response to regional warming. We employed collection of surface spectra using a portable spectroradiometer during the 2011 field season. We use high resolution satellite imagery to evaluate snow patch and wetted zone dynamics. Changes in surface moisture are monitored through analytical inversions from satellite imagery. The project was supported under NSF EAGER.

Our team was the first to map and characterize supraglacial channels and establish hydrologic networks responsible for routing surface melt. We established three primary hydrologic networks and their prevalence throughout the ablation zone. These networks drive mass transfer between lakes impacting drainage behavior and supply crevasses and moulins which are the most efficient mechanisms for meltwater injection to the base of the ice sheet.

We are collaborating with Lora Koenig to understand the implications of newly discovered lake subsurface water stored over the winter. We are employing satellite data analysis to corroborate spatio-temporal variability in lakes with observed subsurface water from IceBridge shallow radar data. We are also developing a numerical lake evolution model that will allow us to diagnose conditions responsible for the presence of stored subsurface water. These efforts have been supported under several NASA funded projects.