Deep Ice Stratigraphy and Basal Conditions in Central West Antarctica Revealed by Coherent Radar

We discuss results from a high-sensitivity, multichannel, very high frequency, and surface-based radar depth sounder/imager. The instrument was used to map deep internal layers and characterize basal conditions over a 240-km(2) grid in the vicinity of the West Antarctic Ice Sheet Divide ice core site. The ice thickness at the core site was found to be about 3470 m, and we detected internal layers to within 350 m of the ice/bed interface. Radar-detected layer stratigraphy does not show evidence of flow-induced disturbances that might complicate the depth-age relationship and the interpretation of climate history preserved in the ice. We also found that bed reflectivity over the region varies by more than 30 dB. Approximately 15 dB of this variability appears to be the result of transitions from a frozen to a thawed bed in a number of places. The remainder probably results from changes in bed roughness. Our data are important for planning drilling to the bed, as well as providing constraints and boundary conditions for regional ice-flow models.