Surface Elevation Change
The surface elevation change (SEC) is directly linked to mass balance of the ice sheet. The surface elevation change is a direct measure of the imbalance between the atmospheric forcing and ice sheet dynamics. Hence, identified as an essential climate variable, SEC is derived from present and past ESA radar altimetry missions.
The era of ESA altimetry missions was initiated with ERS-1 in 1992, and data from ERS-2, Envisat and CryoSat-2 have contributed to an unbroken time series from then to present. At present we have two ESA missions contributing with data for the Greenland ice sheet; Cryosat-2 and Sentinel-3a/b ensuring the time series to be continued.
The nature of the radar measurements enables surface penetration in the interior parts of the Greenland ice sheet and the radar measures a reflecting surface within the upper 2 meters of the snow cover, rather than the snow-air interface.