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3rd HyMeX workshop 1-4 June 2009 Heraklion (Gournes), Crete-Greece

The dynamics and balance of water mass transport in the Mediterranean Sea from gravity satellite data

Isabel Vigo (University of Alicante); David Garcia, Ben Chao and Jose M. Sanchez-Reales

The direct observation of water mass from gravity satellite data provides an important independent tool for validating the estimations of the global budget of the Mediterranean Sea. Here we report on our later results on the direct observation of water mass in the Mediterranean region.

Sea Level Variations (SLV) are produced by a combination of steric and mass-induced SLV, which exact combination is a keystone to understand the climate system of the Earth. SLV can be observed by radar altimetry satellites such as TOPEX/Poseidon (T/P) and Jason-1/2. Steric SLV can be computed from in situ measurements of temperature and salinity profiles, or from Ocean General Circulation Models (OGCM) which eventually assimilate those measurements. Mass-induced SLV can be estimated, since 2002, from Time-Variable Gravity (TVG) measurements by the GRACE (Gravity Recovery And Climate Experiment) mission. We revisit this problem in the Mediterranean Sea analyzing the latest release of GRACE data, which are 3 times longer than in previous studies, and the application of non-isotropic filters to reduce the noise in high degree and order Spherical Harmonics (SH) coefficients. The seasonal signal of observed, steric and mass-induced SLV has been re-estimated. It is shown that the non-seasonal SLV are only produced by water mass changes, which Fukumori et al. (2007) proposed to be produced by winds around the Gibraltar Strait. The water net flux through the

Gibraltar Strait has also been estimated joint to its seasonal variation.