HR: 0800h
AN: C41B-0478    [Abstracts]
TI: Detection of Candidate Subglacial Lakes Using ICESat and a Newly Discovered 1000 km**2 Lake System
AU: * Urban, T J
EM: urban@csr.utexas.edu
AF: Center for Spaace Research, Univ. of Texas, 3925 W. Braker Suite 200, Austin, TX 78759, United States
AU: Schutz, B E
EM: schutz@csr.utexas.edu
AF: Center for Spaace Research, Univ. of Texas, 3925 W. Braker Suite 200, Austin, TX 78759, United States
AB: We examine ICESat laser altimetry over Antarctica spanning 2003-2007. Crossovers are computed between 10 fully-calibrated laser campaigns of approximately 33 days each. Scrutinizing these changes, certain locations appear to exhibit more or less consistent patterns: either elevation increases or decreases, with others exhibiting some fluctuation. Several of these spots can be correlated with the known subglacial lake inventory, and many new areas are observed near catchment boundaries throughout the continent. One newly discovered area in East Antarctica has been identified as a candidate lake, or system of subglacial lakes, affecting surface elevations across an area on the order of 1000 km**2. This distinctive area appears to cross two catchment boundaries, spanning three different drainage basins. This spot is located far enough south to be sampled by more than 30 ICESat repeat tracks. Detailed elevation histories are presented and other properties of this new lake system are investigated. Given the exceptional performance and data characteristics of ICESat (2-3 cm precision, less than 10 cm accuracy, 170 m along-track resolution, latitudes to 86 deg.), a quick method for detecting localized elevation variability, or candidate active subglacial lake regions, is via crossover computation. Crossover analyses are more efficient computationally and more accurate than repeat-track analyses which will contain some level of cross-track slope and/or interpolation errors. However, data density of repeat-track methods are nearly an order of magnitude greater than crossovers for ICESat, and therefore suspected regions can be targeted for follow-up study in smaller dedicated repeat-track analyses. The accuracy of ICESat is sufficient for direct crossover height differences to be used in the calculation of rates of elevation. We show elevation rates derived from ICESat crossovers and illustrate their spatial and temporal variability. We then define certain characteristics at the crossovers (based on elevations rates), and later repeat-track elevation profiles, which help to detect candidate subglacial lakes, based upon characteristics of known active water systems, including the newly discovered subglacial system.
DE: 0726 Ice sheets
DE: 0730 Ice streams
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1827 Glaciology (0736, 0776, 1863)
DE: 1855 Remote sensing (1640)
SC: Cryosphere [C]
MN: 2007 Fall Meeting