Improved retrieval of land ice topography from CryoSat-­2 data and its impact for volume change estimation of the Greenland Ice Sheet

Johan Nilsson, Alex Gardner, Louise Sandberg Sørensen, Rene Forsberg
2016 The Cryosphere Discussions  
A new methodology for retrieval of glacier and ice sheet elevations and elevation changes from CryoSat-2 data is presented. Surface elevations and elevation changes determined using this approach show significant improvements over ESA's publically available Cryosat-2 elevation product (L2 Baseline-B). This when compared to near-coincident airborne laser altimetry from NASA's Operation IceBridge and seasonal height amplitudes from the Ice, Cloud, and Elevation Satellite (ICESat). <br><br>
more » ... g this methodology to CryoSat-2 data collected in Interferometric Synthetic Aperture mode over the high relief regions of the Greenland ice sheet we find an improvement in the root-mean-square-error (RMSE) of 27 % and 40 % compared to ESA's L2 product in the derived elevation and elevation changes, respectively. In the interior part of the ice sheet, where CryoSat-2 operates in Low Resolution Mode, we find an improvement in the RMSE of 68 % and 55 % in the derived elevation and elevation changes, respectively. There is also an 86 % improvement in the magnitude of the seasonal amplitudes when compared to amplitudes derived from ICESat data. These results indicate that the new methodology provides improved tracking of the snow/ice surface with lower sensitivity to changes in near-surface dielectric properties. <br><br> To demonstrate the utility of the new processing methodology we produce elevations, elevation changes and total volume changes from Cryosat-2 data for Greenland Ice Sheet during the period Jan-2011 to Jan-2015. We find that the Greenland Ice Sheet decreased in volume at rate of 289 &amp;pm; 16 km<sup>3</sup> a<sup>&amp;minus;1</sup>, with high inter-annual variability and spatial heterogeneity in rates of loss. This rate is 65 km<sup>3</sup> a<sup>&amp;minus;1</sup> more negative than rates determined from ESA's L2 product, highlighting the importance of Cryosat-2 processing methodologies.
doi:10.5194/tc-2016-109 fatcat:yxj2qq5r65h2ldckwmtszr3ywu