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Center for Nonlinear Studies |
Small-scale: Below-surface melting on Dry Valley glaciers
The McMurdo Dry Valleys of Antarctica are a polar desert, and melting of ice from the ablation zones of glaciers during the 6-week summer is the primary source of water to streams, lakes, and associated ecosystems. In order to estimate runoff for geochemical and ecological responses to past and future climates, a spatially-distributed melt model was developed for the glaciers of the McMurdo Dry Valleys, Antarctica. A one-dimensional, physically-based surface energy balance model was adapted that includes the transmission of solar radiation within the glacier ice and is implemented in FORTRAN77. Together with over a decade of meteorological and glacier measurements, the model strongly suggests that below-surface melting is a more significant contribution to glacier runoff than surface melt through a solid-state greenhouse effect.
Large-scale: Summer speedup of the western Greenland Ice Sheet
Observations in west Greenland suggest surface meltwater draining through kilometer-thick ice can dramatically increase summer velocity, raising concerns about a positive feedback between warming climate and ice sheet mass loss. Using a spatially and temporally extensive network of GPS observations, we confirm that ice sheet acceleration is widespread and closely linked to surface melt. The subglacial hydrologic system of the ice sheet appears to behave similarly to alpine glaciers, but because subglacial cavities collapse quickly under the thick ice, the ice sheet seems to maintain high basal water pressures and sliding all summer whenever surface melt occurs. Reorganization of the basal hydrologic system during summer leads to fall velocities that are slower than winter and highly variable.