CPOM research on the impact of surface melting on radar penetration in Greenland

An article led by CPOM PhD researcher Inès Otosaka on ‘Surface Melting Drives Fluctuations in Airborne Radar Penetration in West Central Greenland’ has been published in Geophysical Research Letters (August 2020).

Radar waves emitted by satellites can be used to measure changes in surface elevation of the Greenland Ice Sheet. However, they do not reflect off the ice sheet surface itself, but penetrate into the snow to a depth of about 15 m for radar wavelengths of 2.3 cm. When the snow melts, meltwater can percolate into the snow or refreeze at the surface. Layers of refrozen ice sharply reduce the degree of radar penetration and may be mistaken for an elevation increase in radar measurements. In this paper, the researchers combine firn cores and modelled firn densities with seven years of airborne radar data collected during field campaigns in West Central Greenland to quantify this effect. They identify internal layers corresponding to annual stratigraphy within the snowpack and show that more melt means less radar penetration into the firn. The unprecedented surface melting which occurred across Greenland in 2012 caused a sharp reduction in the degree of radar penetration, from 11.5 m to 5.3 m. However, if the effects of penetration are corrected for, radar altimeters can accurately measure the surface elevation of the ice sheet.