9725708 Alley This award is for a coordinated program of data analysis, forward and inverse modeling in support of the West Antarctic Ice Sheet (WAIS) Program. Central to many discussions of West Antarctic stability is the behavior of ice stream C, the lower part of which slowed greatly about a century ago. This has variously been interpreted as evidence of stabilizing feedbacks, or of accidental response to ongoing ice sheet drawdown possibly leading to collapse. Microearthquake observations on ice stream C provide an especially sensitive probe for ice stream motion and behavior, allowing detection of basal motion, and characterization of basal lubrication, flow resistance (sticky spots), flow properties, and response to changing stresses caused by tidal processes or nearby microearthquakes. Using an existing data set, the size, spacing and strength of resistive sticky spots, the rheology of the lubricating material between sticky spots, and the spatial variability of these across seven monitoring stations along still-active and nearly-stopped regions of the ice stream will be determined. Assimilation of these data will require modeling of the ice stream, its basal system and its coupling to the floating ice shelf down glacier. Both forward and inverse modeling will be used to learn more about the ice streams and the parameters that control their behavior. This work should improve our knowledge of the physics of ice stream basal lubrication and ice shelf/ice stream coupling.
