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Title: Characterization of Deep Internal Layers and Basal Conditions Around the WAIS Divide Drill Site by Surface-Based Radar
Author: Laird, C.M., Blake, W.A., Gogineni, P.S., Allen, C.T., Leuschen, C.J. and Braaten, D.A.
Periodical: American Geophysical Union, Fall Meeting 2008, abstract #C31A-0463
Abstract: We used an ultra-wideband, very high frequency (120 to 300 MHz) surface-based radar to simultaneously map ice thickness, deep internal layers and the ice-bed interface around the West Antarctic Ice Sheet (WAIS) Divide deep drill site at a fine resolution. The radar was built by the Center for Remote Sensing of Ice Sheets (CReSIS) as part of the Polar Radar for Ice Sheet Measurements (PRISM) project with the main goal of developing and testing surface-operated radars to characterize ice thickness and bedrock conditions in Antarctica and Greenland. The system was fine-tuned in the field to a center frequency of 150 MHz with a bandwidth of 20 MHz to produce greater sensitivity. The survey covered a 30 km by 8 km area with 1-km line spacing along a polar stereographic grid that overlapped both the drill site and the WAIS Divide. The data have been processed for general use and are available on the CReSIS website (www.cresis.ku.edu). Echograms and digital ice thickness, bed elevation and bed reflectivity maps have been produced while analysis continues. Our major findings to date include: 1) internal layers are observed nearly continuously to 2800 m depth, as much as 500 m below the deepest previously mapped layers in this region, 2) internal layers have been detected to within 350 m of the bed, covering about 90% of the ice thickness, 3) ice thickness varies between approximately 3100 m and 3550 m over the grid and is about 3500 m at the drill site, 4) basal returns were mapped nearly continuously along grid lines and vary by more than 30 dB, indicating a wet bed at the drill site and frozen conditions elsewhere. The data will aid rigorous interpretations of the WAIS ice cores (including impurity records and the depth/age scale) and the morphology and evolution of the WAIS (mean annual accumulation rates, spatial extent, divide migration and volcanism). Fine-resolution information on deep internal layers, basal conditions and ice thickness/bed elevation will help refine glacial, sea-level and climate-change histories by constraining both forward and inverse dynamic ice flow models.
Year: 2008