HR: 16:00h
AN: C54A-01    [Abstracts]
TI: Identification and Characterization of Dynamic Alpine Subglacial Lakes Using InSAR, Radio- Echo Sounding, and Crevasse Interpretation
AU: * Capps, D L
EM: dcapps@sfu.ca
AF: Centre for Natural Hazard Research Department of Earth Sciences Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
AU: Rabus, B T
EM: brabus@mdacorporation.com
AF: MacDonald, Dettwiler and Associates Ltd., 13800 Commerce Parkway, Richmond, BC V6V 2J3, Canada
AU: Clague, J J
EM: jclague@sfu.ca
AF: Centre for Natural Hazard Research Department of Earth Sciences Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
AB: We use interferometric synthetic aperture radar (InSAR), radio-echo sounding (RES), and crevasse interpretation to identify and characterize two dynamic alpine subglacial lakes in Glacier Bay National Park, Alaska. Although significant literature exists on large subglacial lakes in Antarctica, little research has been done on alpine subglacial lakes. Subglacial and subaerial glacier-dammed lakes and the catastrophic floods (jokulhlaups) that release are a hazard in glacierized mountain regions around the world. Many glacier-dammed lakes form subglacially during periods of glacier retreat and downwasting, but are not identified until they become subaerially exposed or release a jokulhlaup. The two lakes discussed here are dammed by Brady Glacier in southeast Alaska, 120 km west of Juneau. Initially, a conspicuous, 3-km-long crevasse in the glacier drew our attention to Hinge Lake, so named because of its hinge-like appearance. For the InSAR analysis, we utilized 20 ascending and descending ERS-1 and -2 tandem radar images provided by the European Space Agency. We obtained a DEM from Glacier Bay National Park that was based on data from the SRTM mission, with gaps filled using photogrammetry data. We co-registered and processed raw SAR signal data into complex, single-look images, created interferograms, and unwrapped the phase. To simplify the analysis, we assumed zero horizontal glacier movement. This assumption is valid because ice is flowing into a closed depression and all interferograms analyzed in this study show very little or zero horizontal motion. To further characterize the lakes, we conducted a RES survey to determine ice depths and substrate. We deduced principle stresses by interpreting crevasses patterns in combination with vertical displacement data derived from interferograms. A time series of interferograms shows vertical motion over large areas of the two lakes. A hydraulic connection between the two lakes is inferred from contemporaneous vertical displacement of the overlying ice. The RES survey provided minimum depths of floating ice. We explain crevasse patterns using a two-fold stress field caused by simple downslope ice movement and vertical displacement of the overlying ice due to filling and draining of the lakes. This study demonstrates that a combination of InSAR, RES, and glaciological interpretation can effectively identify and characterize alpine subglacial lakes. Knowledge of these lakes is important for understanding glacier motion, outburst flood potential and routing, and glacier mass balance. This research is a component of a dissertation that seeks to identify and characterize the glacier-dammed lakes of Glacier Bay, Denali, and Wrangell - St. Elias National Parks using ground-truthed radar and optical remote sensing techniques. It is our aim to eventually apply these techniques to glacier-dammed lakes worldwide.
DE: 0720 Glaciers
DE: 0746 Lakes (9345)
DE: 0758 Remote sensing
DE: 1630 Impacts of global change (1225)
DE: 1821 Floods
SC: Cryosphere [C]
MN: 2007 Fall Meeting