CoAuthors

Meyssignac Benoit (LEGOS-CNES, France); Couhert Alexandre (CNES, France); Mercier Flavien (CNES, France); Zawadszki Lionel (CLS, France); Michael Ablain (CLS, France); Annabelle Ollivier (CLS, France)

As the dominant reservoir of heat uptake in the climate system (93% of the total Earth heat uptake is located in the ocean [Levitus et al. 2012]), the ocean provides a critical measure of the Earth energy imbalance at the top of the Atmosphere. The ocean heat uptake can be inferred through the thermal expansion of the ocean estimated either directly from in situ Temperature profiles or indeirectly with the sea level budget appraoch by combining satellite altimetry and GRACE observations. In this study we revisit the sea level budget approach and propose new estimates of the deep ocean warmimg and the Earth energy imbalance with reduced error bars (compared to previous studies such as Llovel et al. 2014) .
In past studies GRACE and satellite altimetry observations have been estimated and combined in the international reference frame (ITRF). The ITRF is centered on the center of figure of the Earth (CF) which implies that both GRACE and satellite observations have been considered with respect to the CF. But GRACE and satellite altimeters move around the center of mass of the Earth (CM) and the projection of their observations in reference frames centered on the CF generate significant level of uncertainty in the data. In this study we combine Grace and satellite altimetry in a reference frame centered on the CM to remove this source of uncertainty. We use new satellite altimetry products and new GRACE observations reprocessed with orbits centered on the CM. It enables to close the sea level budget over the period 2005-2015 with unprecedented accuracy and to improve estimates of the deep ocean warming and the Earth energy imbalance.