On the relationship of satellite retrieved surface temperature fronts and chlorophyll-a in the Western South Atlantic

SARACENO, M., C. PROVOST AND A. R. PIOLA

JOURNAL OF GEOPHYSICAL RESEARCH

Año: 2005 p. 1 - 16

0148-0227

The time-space distribution of chlorophyll a in the southwestern Atlantic is examinedusing 6 years (1998–2003) of sea surface color images from Sea-viewing Wide Fieldof View Sensor (SeaWiFS). Chlorophyll a (chl a) distribution is confronted with seasurface temperature (SST) fronts retrieved from satellite imagery. Histogram analysis ofthe color, SST, and SST gradient data sets provides a simple procedure for pixelclassification from which eight biophysical regions in the SWA are identified, includingthree new regions with regard to Longhurst (1998) work: Patagonian Shelf Break (PSB),Brazil Current Overshoot, and Zapiola Rise region. In the PSB region, coastal-trappedwaves are suggested as a possible mechanism leading to the intraseasonal frequenciesobserved in SST and chl a. Mesoscale activity associated with the Brazil Current Frontand, in particular, eddies drifting southward is probably responsible for the high chl avalues observed throughout the Brazil Current Overshoot region. The Zapiola Rise ischaracterized by a local minimum in SST gradient magnitudes and shows chl a maximumvalues in February, 3 months later than the austral spring bloom of the surroundings.Significant interannual variability is present in the color imagery. In the PSB, springs andsummers with high chl a concentrations seem associated with stronger local northerlywind speed, and possible mechanisms are discussed. Finally, the Brazil-Malvinas front isdetected using both SST gradient and SeaWiFS images. The time-averaged position of thefront at 54.2
W is estimated at 38.9
S and its alongshore migration of about 300 km.