Constraining Basal Conditions across the Amundsen Sea Embayment of West Antarctica using a Synthesis of the PASIN and HiCARS Radar Sounding Data

Recent observational studies and models have shown that ocean forcing, bed topography, and basal conditions are major controls of the behavior of the Amundsen Sea Embayment of the West Antarctic Ice Sheet. This region contains Thwaites Glacier and Pine Island Glacier, the two most rapidly changing glaciers in Antarctica. Because they are adjacent, interactions between these two glaciers could potentially cause further destabilization as either glacier retreats. Accordingly, it is important to understand the basal conditions on the Thwaites-Pine Island boundary in order to accurately model the present and future behavior of these glaciers. Previous airborne geophysical surveys in this area have provided dense radar sounding coverage using multiple radar sounding systems, including the UTIG HiCARS system and the BAS PASIN system used in the 2004 AGASEA survey. Because the boundary region between Thwaites and Pine Island Glacier is at the respective boundaries of the UTIG and BAS surveys, accurate characterization of the basal conditions requires a synthesis of the data produced by the BAS and HiCARS systems. To this end, we present estimates of bed reflectivity spanning both glacier catchments. These estimates were produced using empirically determined attenuation rates. To improve the consistency of these attenuation rates, we fit across a two-dimensional area, rather than a one-dimensional line as in previous work. These estimates also include cross-calibration to account for the radar sounding systems' differing power and center frequency. This will provide the first cross-survey map of basal reflectivity spanning the entire Amundsen Sea Embayment.