Surface Melting Drives Fluctuations in Airborne Radar Penetration in West Central Greenland

Abstract

Greenland Ice Sheet surface melting has increased since the 1990s, affecting the rheology and scattering properties of the near-surface firn. We combine firn cores and modeled firn densities with 7 years of CryoVEx airborne Ku-band (13.5 GHz) radar profiles to quantify the impact of melting on microwave radar penetration in West Central Greenland. Although annual layers are present in the Ku-band radar profiles to depths up to 15 m below the ice sheet surface, fluctuations in summer melting strongly affect the degree of radar penetration. The extreme melting in 2012, for example, caused an abrupt 6.2 ± 2.4 m decrease in Ku-band radar penetration. Nevertheless, retracking the radar echoes mitigates this effect, producing surface heights that agree to within 13.9 cm of coincident airborne laser measurements. We also examine 2 years of Ka-band (34.5 GHz) airborne radar data and show that the degree of penetration is half that of coincident Ku-band.