Mass changes of the Greenland and Antarctic Ice Sheet from GRACE and GRACE-FO: products, validation and interpretation

Gravimetric Mass Balance (GMB) products for the ice sheets in Greenland (GIS) and Antarctica (AIS) were derived within the ESA Climate Change Initiative continuation projects GIS_cci+ and AIS_cci+, respectively. We made use of the entire series of time variable gravity fields acquired by GRACE and its successor GRACE-FO (Follow-On), spanning almost 19 years between 2002 and 2020. Our products are based on the monthly solution series CSR RL06, which was chosen based on a quality assessment conducted for a wide range of available solutions. The GMB product comprises (a) time series of monthly mass changes for the whole ice sheet and for individual drainage basins, and (b) gridded mass changes covering the entire ice sheet. For GIS we compare two variants of GMB products derived by means of differing methods, i.e. from a regional integration approach based on tailored sensitivity kernels applied by TU Dresden and from a point mass inversion approach utilised by DTU Space. All products are freely available through the project websites and an interactive data portal hosted at TU Dresden (data1.geo.tu-dresden.de).

The GMB products allow us to study temporal variations in the ice sheets’ mass balance from the basin integrated time series. Changes in the spatial mass balance patterns are quantified by means of the gridded products. Independent data sets are used to validate our products. To validate the full mass change signal of the AIS, comprising both changes in ice dynamics and surface mass balance (SMB), we make use of an Antarctic mass change time series from a multi-mission satellite altimetry analysis. For both ice sheets, changes in cumulated SMB variations predicted by a regional atmospheric climate model (i.e. RACMO2.3p2) are compared to the GMB basin products. This intercomparison is limited to temporal components not related to changes in ice dynamics (e.g. seasonal variations). Both independent data sets bridge the gap between GRACE and GRACE-FO, providing valuable information to ensure a seamless continuation of the GRACE time series by GRACE-FO.