Biophysical Regions and Surface Fronts in the Western South Atlantic

SARACENO, M.

Portland, OR, USA

Congreso; AGU Ocean Science Meeting; 2004

Biophysical Regions in the Western South Atlantic are studied based on the analysis of 5 years (1998-2002) sea surface colorimages from SeaWiFS. Seven different regions are defined considering the spatio-temporal distribution of chlorophyll-a: Shelf BreakFront (SBF), Brazil-Malvinas Overshoot (BMO), Brazil-Malvinas Front (BMF), Costal Fronts (CF), Continental Shelf (CS), Malvinas andBrazil Currents (MBC) and Zapiola Ridge (ZR). All regions present a seasonal cycle with a strong component of interannual variability.Chlorophyll-a concentrations can reach 10 mg/m3 and maxima usually occur during spring. Regions are compared to sea surfacetemperature fronts from AVHRR imagery. There is not a direct relationship between SST frontal regions and chlorophyll-aconcentrations. In CF regions SST fronts and chlorophyll-a maxima coincide in position but not always in time. The strong signatureof the Subantarctic Front (SAF) derived from SST images is only well identified in SeaWiFS images within the SBF region; neither thearea corresponding to the Falkland Escarpment nor the Malvinas Return Front are evident in chlorophyll-a. The BMF is present inboth SST and SeaWiFS images. Its range of meridional migration around 38$\deg$S and following the 1000m isobath is ofapproximately 250 Km with both satellite data. Bathymetry and physical forcing like tides and mesoscale dynamics are investigatedto explain the variability of the Biophysical Regions.