HR: 15:25h
AN: C53A-08    [Abstracts]
TI: Subglacial water transport throughout Antarctica from ICESAT laser altimetry
AU: * Smith, B E
EM: ben@ess.washington.edu
AF: University of Washington Applied Physics Lab, 1013 NE 40th Street Box 355640, Seattle, WA 98105-6698, United States
AU: Joughin, I R
EM: ian@apl.washington.edu
AF: University of Washington Applied Physics Lab, 1013 NE 40th Street Box 355640, Seattle, WA 98105-6698, United States
AU: Fricker, H A
EM: hafricker@ucsd.edu
AF: Institute of Geophysics and Planetary Physics, Scripps Oceanographic Institution, 9500 Gilman Drive, 0210, La Jolla, CA 92093, United States
AU: tulaczyk, s
EM: tulaczyk@pmc.ucsc.edu
AF: Earth & Planetary Sciences, Earth & Marine Sci., Santa Cruz, CA 95064, United States
AB: A survey of the Antarctic ice sheet using satellite laser altimetry has detected 46 small regions of surface uplift or drawdown in twelve different glacier drainages around Antarctica. Surface displacements are measured relative to the best-fitting plane passing through multiple (5-11) elevation measurements on the same repeat-track, allowing correction for across-track slopes. Volume displacements are derived by interpolating displacements from multiple tracks to a common grid. These ECAs (Elevation Change Anomalies) range from less than four km to more than 60 km across, with vertical displacements ranging from a few decimeters to over ten meters. Typical volume displacements are on the order of 0.05 cubic kilometers over the three-year survey, and the largest displacement is more than 1.4 cubic kilometers. Although the majority of the ECAs are within the Filchner- Ronne catchment, others (including those discussed by Fricker and others, 2007), are found in the Ross Embayment, in the drainages of Byrd Glacier and Lambert Glaciera, and in the interior of Wilkes Land. As have other researchers who have observed ECAs, we take these features to result from water motion at the bed. In all cases where the ice sheet velocity structure is known, the ECAs are in regions of ice stream or tributary flow, which implies that they are associated with melting bed conditions. Some of the ECAs appear to be downstream of linear features in the ice sheet surface, suggesting that they are associated with local minima in the hydraulic potential at the bed. Others have no clear association with surface topography. The relatively small number of ECAs precludes drawing strong conclusions about spatial and temporal correlations between filling and drainage events. However, a few conclusions are clear: Because adjacent ECAs are more likely to have correlated filling or drainage rates than to have anticorrelated filling or drainage rates, it does not appear that water is conserved among the ECAs. This suggests that the ECAs exchange water with other water systems at the bed. Of critical importance for our understanding of ice stream dynamics is whether inflation of the ECAs represents a withdrawal of water from the system that lubricates fast basal motion. If the correlation of drainage and filling over distances of hundreds of kilometers is not coincidental, it suggests either that large-scale channel systems connect the ECAs, or that filling or drainage is triggered by large-scale velocity variations.
DE: 0726 Ice sheets
DE: 0730 Ice streams
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
SC: Cryosphere [C]
MN: 2007 Fall Meeting