Seasonal and interannual variability of the southern south Equatorial Current bifurcation and meridional transport along the eastern brazilian edge.

Dóris R A VELEDA, Moacyr ARAÚJO, Marcus SILVA, Raul MONTAGNE, Rodolfo ARAÚJO


The dynamics of the southern band of the South Equatorial Current (sSEC) near to Brazilian shelf is investigated using recent field observations and a regional numerical modeling approach. The field measurements were obtained from five moorings deployed by German CLIVAR (Climate Variability and Predictability Program) cruises (March 2000- August 2004) along a crossshore line at 11oS. The Regional Ocean Model (ROMS) is used to simulate the circulation and thermohaline structures within the ocean area comprised between 5°S-25°S and 20°W-47°W. This integration domain was covered by an isotropic 1/12o horizontal grid and 40 terrain-following layers. The numerical results confirm a seasonal migration of the sSEC divergence along the Brazilian edge, as well as its depth dependence with a maximum southward shift in July at 200 m depth, while a maximum northward displacement occurs in November at this same depth. This intrannual variability coincides with the North Brazil Undercurrent (NBUC) seasonality at 11oS from moorings measurements. Empirical Orthogonal Function (EOF) and numerical results show a minimum NBUC strength during November and a maximum northward transport in July. The mean transport from field measurements is 25Sv while this from numerical simulations is 24.5Sv. The SODA reanalysis with 47 years of monthly mean indicates that the sSEC has not only a seasonal variability as well as quasi-biannual variability.

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