Satellite Gravity Models and Their Use for Estimating Mean Ocean Circulation

One of the main fields of application of static gravity field models is the determination of the (geodetic) mean dynamic ocean topography (MDT) as the difference of a mean sea surface derived from multi-year satellite altimetry, and a high-resolution static geoid model. In this study the performance of several satellite-only global gravity models is evaluated based on the MDT and derived geostrophic ocean surface currents. These are the GRACE-only model ITG-Grace2010S, the GOCE-only model GOCE_TIM_R2, and the combined gravity model GOCO02S representing a consistent combination of GRACE and GOCE. The geodetic MDT results are validated against independently measured drifter data. Compared to GRACE, the new high-resolution GOCE models improve the estimates of the mean dynamic ocean topography, filtered to degree/order 180, by reducing the differences to the drifter data by 10-12 cm/s. Therefore, they contribute significantly to an improved knowledge of mean ocean circulation.