Strong Potential for the Detection of Refrozen Ice Layers in Greenland's Firn by Airborne Radar Sounding

Abstract

The formation of impermeable ice layers within Greenland's firn can significantly increase surface meltwater runoff by capping percolation, thus increasing the continent's immediate contributions to sea level rise. Detection of these layers by airborne radar sounding would permit large scale assessment of their spatial coverage and temporal evolution. We present an electromagnetic forward model for radar scattering in dry firn, as well as a statistical model of firn density profiles, which together allow us to robustly simulate airborne radar sounding measurements in the ice sheet near-surface. We use these models to simulate the response of the University of Kansas Accumulation Radar to refrozen ice layers thinner than the radar vertical resolution. Our results suggest that continuous ice layers are detectable as anomalously bright reflections within the firn, so long as the background density does not exceed 0.72 g/cm3. We find that approximately 81% of single ice layers thicker than 2 cm are detectable, as well as over 90% of all multi-layer configurations. This suggests that the Accumulation Radar is an effective tool for studying the spatial and temporal coverage of thin ice layers in Greenland's firn, but such a survey would likely still underestimate the total areal extent.