Research

A new ocean mean dynamic topography model, derived from a combination of gravity, altimetry and drifter velocity data

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Abstract

We present a new mean dynamic ocean topography product based on the improved geoid model, derived in the Optimal Geoid for Modelling Ocean Circulation (OGMOC) project supported by the European Space Agency. This geoid model is based on the Gravity Recovery and Climate Experiment (GRACE) and the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite missions combined with the newer DTU15GRA altimetric surface gravity and it was optimized to eliminate artificial features common for other geoid models such as striations and orange skin. Subsequently, the model has been augmented using the EIGEN-6C4 coefficients to harmonic degree 2160. The new geodetic mean dynamic ocean topography model DTU17MDT has been derived using this geoid model and the DTU15MSS mean sea surface, with the quasi-gaussian filter optimized to best fit velocities of oceanographic drifting buoys. The new model improves the resolution of important details of the ocean circulation. Finally, the drifter data were integrated into the model to refine its spatial resolution. The new topography product DTU17cMDT, combining the wealth of information from satellite gravity and altimetry and drifters, is rich with more features of the ocean surface circulation. In particular, as shown in the case of the Gulf Stream off the east coast of Florida, DTU17cMDT improves description of the western boundary currents.