Envisat-derived elevation changes of the Greenland ice sheet, and a comparison with ICESat results in the accumulation area

We show, for the first time over the Greenland ice sheet, that an along track method for deriving rates of elevationchange can successfully be applied to Envisat radar altimetry data (2002–2010). The results provide improved resolution and coverage compared to previous results obtained from cross-over methods. Also, we find that temporal changes in the elevation change rate can be derived from Envisat data, and show clearexamples of this by generating five-year running means for selected areas of the Greenland ice sheet. For a period between 2003 and 2009, the elevation of the ice sheetswas measured by both the laser altimeter on board ICESatand the radar altimeter on board Envisat. We compare rates of elevation change derived from ICESat and Envisat for this time span inwhich both sensors were operating.We focus on the area above the equilibrium line altitude, in order to specifically derive information on snow parameters. A comparison of the elevation changes observedby the two sensors shows a complex pattern, which can be explained regionally by model output describing the changes in both firn air content and accumulation rates.