INTERGEO Agenda - english

Major applications of the GRACE and GRACE-FO satellite gravimetry missions address mass redistribution of water and ice on the Earth’s surface, often with a direct link to climate research. Such applications are commonly based on global gridded datasets of mass distribution anomalies. Such Level 3 data products from satellite gravimetry are derived by individual institutions either directly from Level-1 observations or from Level-2 gravity field solutions. Different Level-3 products use different methodologies and therefore yield different results. This contribution examines and compares, both qualitatively and quantitatively, the Level-1-based Mascon data products from the Jet Propulsion Laboratory (JPL), the Goddard Space Flight Center (GSFC) and the Center for Space Research (CSR), as well as a data product based on Level-2 data from the Technische Universität Dresden (TUD). Various components of temporal changes are considered, such as mean linear change, seasonal signals, and non-linear and non-seasonal components. Furthermore, the integrated mass changes of selected regions are analysed and compared. These include the Antarctic and Greenland ice sheets, as well as ocean areas adjacent to the ice sheets. The results show that the four products are largely consistent in terms of the temporally mean rate of mass change. Significant discrepancies occur primarily over the ice sheets and cover less than 3% of the Earth’s surface. A comparison of the annual signal reveals that the TUD product differs from the other products in certain locally confined coastal regions. Furthermore, spatially coherent phase differences in the seasonal component of ocean mass changes are observed, which can be attributed to differences in the treatment of the atmospheric background model. Small-scale differences resulting from different grid size definitions are observed between all products. The results of the integrated mass change over the Antarctic and Greenland ice sheets show that all products show ice-sheet mass loss and that the linear trend varies by a maximum of 20 Gt. However, when considering the ocean areas adjacent to the ice sheets, clear differences become apparent. Here, the various products show trends that are, in some cases, contradictory. This can be explained by the different strategies employed to avoid leakage effects. It highlights the need for further research into method comparison and method development.