GRACE and satellite altimetry to measure ocean mass and density changes between 2002 and 202

Abstract

From GRACE and GRACE-FO we get time variable information from the Earth’s gravity field since 2002. The monthly time series obtained from science centers can be represented as a surface water layer. By sampling the oceans at mascons we obtain a mass against time signal which represents the barystatic component of the sea level rise signal which is confronted with satellite altimetry since 1992, the combination of both geodetic results allows to estimate the density change in the ocean domain for which profiling float measurements can be used as an independent source. Of particular interest is the effect of glacial isostatic adjustment which shows up in both gravimetry and altimetry. The GIA correction determines for a part the implementation of the geocenter correction that is used during the GRACE data processing. Depending on the processing choices to represent ocean mass and the GIA correction that is required we find barystatic sea level rates varying between 1.9 and 2.4 mm/yr whereby we remark that the uncertainty is larger than previously expected. The volume change in the oceans is remarkably stable, it remains at 3.7 mm/yr with a noticeable acceleration of 0.2 mm/yr2. This means that the density change due to temperature and salinity changes in the ocean domain varies between 1.3 and 1.8 mm/yr.