CoAuthors

Felix Müller (DGFI, Germany); Denise Dettmering (DGFI, Germany); Christian Schwatke (DGFI, Germany)

Since the significant improvements of the Earth gravity field by GRACE and GOCE a space-based dynamic ocean topography can be derived by subtracting geoid heights N of a satellite-only gravity field from altimetric sea surface heights h. As the geoid heights are smooth compared to the spatial along-track resolution of altimetry a consistent filtering of both, N and h, is essential. The profile approach developed at DGFI (Bosch & Savcenko 2010) applies a consistent filtering and provides estimates of the instantaneous dynamic ocean topography (iDOT) along individual ground tracks of any altimeter mission. Thereby multi-mission iDOT-profiles allow studying the variability of the dynamic ocean topography.
In the present study we validate the time-variable dynamic ocean topography by gridding the iDOT-profiles, computing the associated geostrophic velocity field and comparing this with surface currents observed by ARGO floats and Ekman-corrected surface drifters. Spatial and temporal resolution are to be adapted to the availability of the surface current data. We are going to demonstrate that although the gridded iDOT time series provides a smoothed snapshot of the dynamic ocean topography the consistency with the in-situ data is better than with any long-term mean dynamic topography.