HR: 1340h
AN: C33B-0350    [Abstracts]
TI: Rapid Ice Flow Related Topography from ICESat Altimetry in NE Greenland
AU: * Shuman, C A
EM: Christopher.A.Shuman@nasa.gov
AF: Oceans and Ice Branch, Laboratory for Hydrospheric Processes, NASA Goddard Space Flight Center, Code 971, Room A210, Building 33, Greenbelt, MD 20771 United States
AU: Fahnestock, M A
EM: Mark.Fahnestock@unh.edu
AF: Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Morse Hall, 39 College Road, Durham, NH 03824 United States
AB: Extending approximately 700 km inland from the coast of Greenland, the `Bronlund' Ice Stream in Northeast Greenland has a clear influence on the topography of the ice sheet from the coast to near the central divide. This onset of flow in this feature is associated with high rates of basal melt; flow in the interior is characterized by high strain rates in distinct shear margins. Fahnestock et al. (2001) investigated the topography and ice flow patterns in the interior based on data from SAR interferometry from Joughin et al. (2001). In this paper, we use ICESat precision laser altimetry data to examine the morphology of the shear margins of this feature. ICESat's high frequency sampling, 172 m along-track, provides consistent and accurate elevation data on the relief associated with the shear margins and surface undulations in the stream itself. The marginal shear zones and the undulating internal topography that define the ice stream are clearly illustrated by the sampling of the ICESat data. Repeat tracks obtained during ICESat's first four operational periods enable the impact of clouds on the elevation data to be minimized. The resulting pattern of ICESat tracks, supported by enhanced MODIS imagery, allows us to revisit the previous study based on interferometry, enabling us to study the dynamically generated topography using a consistently sampled set of detailed elevation profiles over large areas. Narrow marginal troughs are shown to be as much as 10 m deep over distances of a kilometer; this is pronounced topography in ice 3 km thick. The relief and extent of the marginal trough on the southeastern edge of the stream is in contrast to the less well-pronounced margin on the northwest. Significant surface undulations, with horizontal extents of approximately 3 ice thicknesses, are found where ice stream flow speeds reach 50 m/year, and change character downstream as flow speeds increase. Changes in the positions of the marginal troughs may be discernable if the ICESat instrument, or a follow-on mission, repeats the same tracks in a few years with similar accuracy.
UR: http://icesat.gsfc.nasa.gov/
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 1894 Instruments and techniques
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting