Evidence for and Against Temperate Ice in Antarctic Shear Margins From Radar-Depth Sounding Data

Abstract

The majority of ice mass loss from Antarctica flows through narrow, fast sliding regions of ice. The lateral boundaries of these regions, termed shear margins, are characterized by lateral shear strains in excess of ∼10−3 yr−1. Shear heating within these margins could warm ice significantly–even to the melting point–but other processes such as lateral advection of cold ice and fabric development compete with this effect. Radar observations can help constrain where temperate ice exists because englacial temperature increases electric conductivity which increases radar attenuation. We utilize the temperature-dependent attenuation of ice to develop a novel method for constraining englacial temperature in shear margins by combining existing thermal models with very high frequency radar depth-sounding data. We find evidence supporting temperate shear margins in 18 locations and find evidence for non-temperate margins in 37 locations, notably in the Amundsen Sea Embayment.