CoAuthors

Benoit Meyssignac (LEGOS/CNES, France); Jean Michel Lemoine (CNES, France); Alexandre Couhert (CNES, France); Flavien Mercier (CNES, France)

The comparison with in situ Argo profiles and GRACE-based ocean mass has proven to be useful to detect global and regional drift in sea level estimates from satellite altimeters. It is also routinely used to assess the impact of new altimeter standards in sea level products and detect anomalies at interannual time scales. So far, the classical approach is to estimate the steric sea level from a combination of GRACE and satellite altimetry observations and validate it against Argo observations. Historically, GRACE and satellite altimetry data are combined in a reference frame centered on the center of figure of the Earth (CF) for this purpose. This approach is sensitive to the uncertainty in the geocenter motion which limits significantly the accuracy of the cal/val method at both global and regional scales. Yet, GRACE and satellite altimeters move around the center of mass of the Earth (CM) and theoretically the projection of GRACE and altimetry observations in reference frames centered on the CF is not necessary for the cal/val. In this study we combine for the first time new satellite altimetry products with new GRACE observations reprocessed with orbits centered on the CM. We compare this combination with Argo data at both global and regional scale. This approach enables to remove the source of uncertainty associated with the geocenter motion and enables to reach an unprecedented accuracy in the cal/val method based on Grace and Argo.