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

Abstract

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.

Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurements

“…Earlier studies (e.g. Watts and Kontoyiannis, 1990;Johns et al, 2005;Kanzow et al, 2006;Cunningham, 2009) found that subtracting a least-squares exponentiallinear fit of the form P Drift (t) = a 1 − e −bt + ct + d from the pressure time series to be the procedure that works best for the PIES. As the SBE26plus recorders were also equipped with quartz pressure sensors, we decided to "de-drift" all five sensors similarly by subtracting exponential-linear fits as described above.…”

Influence of El Niño Wind Stress Anomalies on South Brazil Bight Ocean Volume Transports

“…The BC has been studied by numerous researchers who predominantly attempted to estimate its meridional volume transport based on hydrographic datasets acquired at different latitudes [1,2]. Only a few studies in the scientific literature treat specifically about the interannual variability of the BC volume transport even though many studies describing general dynamic aspects in different variability scales for the whole South Atlantic basin had been published such as Schott et al [3], Stramma et al [4], Lumpkin and Garzoli [5] and Veleda et al [6]. Goni et al [7], using satellite-derived sea height anomaly and sea surface temperature (SST) observations from 1993 to 2008, observed low-frequency variability of the BC front.…”