Global ocean mass estimates from GRACE and GRACE-FO, evolution and error analysis.

This study is concerned with the total rate of mass change in the oceans as seen by the GRACE and GRACE-FO missions between Mar-2002 extending to beyond 2023 into the GRACE-FO observation window. We use the same monthly source data in the form of level-2 spherical harmonic coefficients  and find that the selected glacial isostatic adjustment models, ocean mask definitions, and other de-aliasing corrections have a significant effect on the outcome of the barystatic ocean mass rates. In addition to the ICE6G models, and GIA models by Caron and Ivins we also implement GIA models derived from a 3D model forced by ICE-7G ice history. In the end we find barystatic ocean mass rates of change varying between 1.5 to 2.4 mm/yr. The relevance of this result is that the mass component of the sea level change has a larger uncertainty than that we earlier expected. Our conclusion is that it is more difficult to close the sea level budget  which involves ocean volume estimates from satellite altimetry, density estimates from Argo profiling float data and the mass component of sea level changes observed by satellite gravimetry.