HR: 08:45h
AN: C31A-04    [PDF]
TI: ICESAT/GLAS Reveals Ice Sheet Surface Features at Ice Stream Shear Margins in West Antarctica.
AU: * Smith, B E
EM: ben@ess.washington.edu
AF: University of Washington Department of Earth and Space Sciences, box 351310 Johnson Hall 63, Seattle, WA 98195
AB: The shear margins surrounding ice streams are marked by grooves and ridges in the ice surface. These scars remain after ice streams become inactive, recording the structure of the ice streams, and allowing investigations of the history of the ice stream system. The positions of the scars are readily found in satellite imagery of WAIS, but the character of the surface undulations is more difficult to determine. NASA's GLAS (Geoscience Laser Altimeter System) mission has produced several thousand kilometers of high-resolution elevation profiles over the West Antarctic ice streams. These profiles reveal the shape of the margin scars at high vertical and horizontal resoultion. Here I examine the marginal features of both active and passive ice streams, and track their evolution from the inland tributary region to the Ross Ice Shelf. I find the horizontal position of the marginal features using AVHRR (Advanced High Resolution Radiometer) and SAR (Synthetic Aperture Radar) imagery, and determine their vertical structure from GLAS data. Three main factors contribute to the formation of marginal features: The change in basal drag at the edge of the ice stream produces a break in the surface slope. The high strain rate associated with fast flow in the margin produces an effective softening of the ice, leading to flattening of the surface. Changes in the elevation and width of the ice stream produce slope breaks at the outside of the margin where slow-moving ice cannot rapidly respond to changing boundary conditions. I present the results of finite element modeling demonstrating the surface characteristics associated with these three processes and relate them to the features seen in the ice sheet.
DE: 1640 Remote sensing
DE: 1827 Glaciology (1863)
DE: 3210 Modeling
SC: Cryosphere [C]
MN: 2003 Fall Meeting