Surface slope control on firn density at Thwaites Glacier, West Antarctica: Results from airborne radar sounding

Abstract

We derive the surface density variations over Thwaites Glacier from a statistical analysis of airborne High-Capability Radar Sounder surface returns acquired in the 2004-2005 summer. We produce a 5 km gridded map with an estimated ±12.5 kg m -3 accuracy. The background pattern of densities decreases inland from ~ 480 kg m -3 to ~ 350 kg m -3. A remarkable ~ 30 km wide vein-shaped anomaly of up to 570 kg m -3 is located ~ 100 km from the coastline. Density anomalies correspond with surface slope breaks but are not necessarily coincident with smaller slopes. They could result from complex wind-driven snow redistribution and/or refreezing of former snowmelt. This inversion technique can significantly improve surface mass balance calculations to understanding of glacier dynamics at regional scales and is valuable to verify and improve Antarctic climate models. It is also a promising approach for future surface analysis of icy moons by planetary radars. Key Points Surface density of Thwaites Glacier is mapped using airborne radar sounding dataA vein-shaped anomaly is detected parallel to the coastline 100 km inlandSurface density pattern is heterogeneous and controlled by surface slope breaks