Topography and penetration of the Greenland ice sheet measured with airborne SAR interferometry

A digital elevation model (DEM) of the Geikie ice sap in East Greenland has been generated from interferometric C-band synthetic aperture radar (SAR) data acquired with the airborne EMISAR system. GPS surveyed radar reflector s and an airborne laser altimeter supplemented the experiment. The accuracy of the SAR DEM is about 1.5 m. The mean difference between the laser heigh ts and the SAR heights changes from 0 m in the soaked zone to a maximum of 13 m in the percolation zone. This is explained by the fact that the snow i n the soaked zone contains liquid water which attenuates the radar signals, while the transparency of the firn in the percolation zone makes volume sc attering dominate at the higher elevations. For the first time, the effecti ve penetration has been measured directly as the difference between the int erferometric heights and reference heights obtained with GPS and laser alti metry.