Adaptively constraining radar attenuation and temperature across the Thwaites Glacier catchment using bed echoes

Abstract

Englacial temperature is a major control on ice rheology and flow. However, it is difficult to measure at the glacier to ice-sheet scale. As a result, ice-sheet models must make assumptions about englacial temperature and rheology, which affect sea level projections. This is problematic if fundamental processes are not captured by models due to a lack of observationally constrained ice temperature values. Although radar sounding data have been exploited to constrain the temperature structure of the Greenland ice sheet using englacial layers, this approach is limited to areas and depths where these layers exist intact. In order to extend empirical radar-based temperature estimation beyond this limitation, we present a new technique for estimating englacial attenuation rates for the entire ice column using adaptive fitting of unfocused radar bed echoes based on the correlation of ice thickness and corrected bed echo power. We apply this technique to an airborne survey of Thwaites Glacier in West Antarctica and compare the results with temperatures and attenuation rates from a numerical ice-sheet model. We find that the estimated attenuation rates reproduce modelled patterns and values across the catchment with the greatest differences near steeply sloping bed topography.