A 20-year time series of surface elevation changes of the Greenland Ice Sheet derived from radar altimetry as part of ESA’s Climate Change Initiative

The European Space Agency (ESA) is responding to the need for improved climate data through its Climate Change Initiative (CCI). Space-based observations are exploited to provide long-term measurements of Essential Climate Variables (ECVs). In this work, results for the Ice Sheets CCI (http://www.esa-icesheets-cci.org/ ) are presented. Four parameters of ice sheet mass balance indicators are defined for the Greenland Ice Sheet (GrIS): Surface Elevation Changes; Ice Velocities; Calving Front Locations; Grounding Line Locations. Here, output from all four parameters is shown, with an emphasis on Surface Elevation Changes.

As part of the Ice Sheets CCI, a novel combined repeat track and crossover approach has been implemented for Envisat radar altimetry for the period 2002-2010, which resolves changes along the ice margin, as well as in the ice sheet interior. Non-repeat track data for the last two years of Envisat’s mission are also incorporated, using a different method to the one used for previous years. Furthermore, the results extend back in time through inclusion of ERS-1 and ERS-2 radar altimetry data. This provides a 20-year dH/dt of surface elevation changes covering the Greenland Ice Sheet, as well as five-year running means for the entire period showing regional accelerations and decelerations. These results form the input for the Ice Sheets CCI ECV product. Plans for the upcoming CCI extension include extension of the dH/dt series by CryoSat and Sentinel-3 altimetry.