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Estimation of the ocean Mean Dynamic Topography in the Mediterranean and Black Seas by combination of altimetry and GRACE/GOCE geoids

Luciana Fenoglio-Marc(1), Juergen Kusche(2), Matthias Becker(1) and Emil Stanev(3)

(1) Darmstadt University of Technology, Petersenstrasse 13, 64287, Germany
(2) Delft University of Technology, Kluyverweg 1, 2600, Netherlands
(3) Oldenburg University, Carl-von-Ossietzky Str. 9-11, 2503, Germany

Abstract

For the combination of satellite altimetry with the new gravity missions of GRACE and GOCE, the Mediterranean – Black sea region represents an interesting field for modelling and validation.

We investigate the importance of using GRACE and GOCE data regionally in areas dominated by continental shelf and steep topography breaks, were the ocean Mean Dynamic Topography (MDT) is characterised by scales shorter than 50-100 km.

In a first step we study the contribution of the most recent satellite-only gravity field model (EIGEN-GL04S1) for estimating the ocean MDT. This gravity model, derived from GRACE and LAGEOS data, should greatly improve the estimate of the MDT at scales larger than 300 km. The MDT is obtained by subtracting the EIGEN-GL04S1 geoid from a regional altimetric Mean Sea Level Surface over 1993-2005 and by filtering the shorter scales. We compare this synthetic MDT estimates with the mean dynamic topography outputs from regional ocean models.The short scales missing in EIGEN-GL04S1 and in the synthetic MDT are investigated by comparing the short scales of the altimetric MSS and of the mean dynamic topography outputs of ocean models .

In a later step, we will make use of the static high resolution GOCE gravity field and of altimetric sea level heights to derive absolute dynamic ocean topography and to assess the performance of the regional oceanographic models. With simulations and analyses we especially aim at the improvement of the shelf circulation ocean modelling using GOCE data and assimilation of the low resolution MDT. Turbulent eddy kinetic energy simulated in the ocean models with and without assimilation will be considered. The time-varying and mean near-shore transport in regions with different topographic controls (deep sea, slope area, continental shelf) and the water, heat and salt transport along the continental shelf break and shelf regions will be evaluated.

We will use GOCE Level 2 spherical harmonic models as input. Investigations will focus towards the error assessment in the three data sets (gravity models, altimetry, regional oceanographic models) and the combination procedure.

 

Workshop poster

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry