Challenges for Greenland-wide mass balance from Cryosat-2 radar-altimetry

As the Greenland ice sheet warms, a change in the structure of the upper snow/firn occurs. This change further induces changes in the reflective properties of the firn seen from satellite radar altimetry. If not identified as changes in the reflective properties of the firn, these may be interpreted as actual surface elevation changes seen from the satellite radar altimetry (Nilsson et al., 2015).Here, we investigate how to correct the elevation change observed from the ESA Cryosat-2 radar altimetry mission to derive elevation change of the air/snow interface of the Greenland ice sheet. The elevation change of this “real” physical surface is crucial, if the goal is to derive Greenland mass balance as done for LiDAR missions.The investigations look into waveform parameters to correct for the observed bias between Radar and LiDAR observations when using Croysat-2 level-2 data. Based on the knowledge gained by analyzing the elevation change derived from the inclusion of various waveform parameters, we pinpoint the challenges associated with the using Croysat-2 observation in mass balance studies. As for mass balance studies utilizing LiDAR observation (ICESat), a strong firn-modeling component is needed; here the information gained from running such models may also provide input for the correction of radar elevation in to surface elevation.