Mean surface geostrophic circulation of the Mediterranean Sea estimated from GOCE geoid models and altimetric mean sea surface: initial validation and accuracy assessment

Different combinations of the EGM2008 global model and the GOCE space-wise solution are used to estimate the geodetic mean dynamic topography and the corresponding surface geostrophic circulation of the Mediterranean Sea. In order to assess the accuracy of the GOCE-derived products for oceanographic applications, the mean currents obtained from the geoid models are compared with the mean surface geostrophic velocities measured by drifters and satellite altimetry data. The mean dynamic topographies based on GOCE data combined with EGM2008 generally describe the main circulation patterns and dynamical features in the Mediterranean Sea, except in few coastal regions and in the semi-enclosed Adriatic and Aegean Seas, and improve the results obtained with previous geoid models. The root mean square differences between the geostrophic velocities and the GOCE/EGM2008-derived currents are smaller than 10 cm/s in all the sectors of the Mediterranean basin, whereas they are larger than 12 - 15 cm/s using the EGM2008 solution. The minimum discrepancies and the best complex correlation coefficient are achieved from the EGMSPWbc solution based on an order-wise block diagonal approximation of the GOCE error covariance structure.