The Cape Frio Upwelling effect over the South Brazil Bight northern sector 
shelf waters: a study using AVHRR images 
Jo&o A. Lorenzzetti' and Salvador A. Gaeta? 
‘National Institute for Space Research-INPE 
Säo José dos Campos, SP Brazil 
2 Oceanographic Institute of University of Sáo Paulo-IOUSP 
Säo Paulo, SP Brazil 
Comission VII, Working Group 8 
KEY WORDS: “AVHRR, Upwelling, Brazil,Cabo Frio, Nitrate, Chlorophyll a” 
ABSTRACT 
Daily Sea Surface Temperature (SST) maps derived from AVHRR HRPT data have been produced and analysed for the 
SE coast of Brazil and adjacent oceanic waters since September of 1992. For the summertime and beginning of autumn 
strong upwelling events are easily seen in some of these images when cloud coverage permits. A subset of these images 
was analysed together with in sifu hydrographic, nutrients, and phytoplankton biomass data collected during an 
oceanographic cruise of COROAS (Oceanic Circulation in the Western Region of the South Atlantic) project done in the 
central sector of the South Brazil Bight (SBB). For well developed upwelling events‘lasting for more than 10 days, the 
SST maps show very extensive tongues of cold upwelled water being advected southwestward and reaching the center of 
the SBB. The plumes of upwelled water are spatially very well correlated with the upwelled nitrate and phytoplankton, It 
is postulated in this report that the horizontal advection of cold upwelled waters can be one of the important factors 
affecting the chemical and biological characteristics of the shelf ecosystem in regions up to 400 km distant from 
CaboFrio in the central area of the SBB. 
1. INTRODUCTION Cabo Frio upwelling is associated with the 
onshore/offshore seasonal migration of the South Atlantic 
The South Brazil Bight (SBB) is defined as the area of the =~ Central Water (SACW) at the continental slope. Recent 
Brazilian Southeastern continental shelf extending from studies have shown that the SACW is the source of the 
Cabo Frio (23°S; 42°W) to Cabo Santa Marta (28.5°S; ^ cold waters that crop up near the coast in this region 
48.6°W) (Fig. 1). At the northern limit of this region, and (Valentin et al., 1987, Gaeta et al., 1994). In some cases of 
a few hundred kilometers north of it, a common feature strong NE winds, persisting for several days, strong 
present on the inner and mid-shelf is a seasonal signal of a ^ upwelling can be developed with surface temperatures 
wind driven coastal upwelling. This upwelling is primarily ^ dropping to 13-14°C near the coast, close to Cabo Frio 
forced by the prevailing NE wind, associated with the ^ These temperatures are about 10?C cooler than the mid 
large scale atmospheric high pressure center present over and outer shelf surface waters. For the synoptic time scale 
the South Atlantic. of 6 -11 days, with the passage of cold fronts over the 
region, the surface winds rotate counterclockwise and 
The negative surface temperature anomalies associated ^ blow for a few days from the southern quadrant inhibiting 
with the upwelling build up during early spring the upwelling. 
(September) and lasts throughout the summer and a few 
months later (March and April). During the fall and winter ~~ Western boundary regions of the oceans are dinamically 
seasons, there is a relaxation of the upwelling (Stech et al., quite different from the regions along eastern octal 
1995). It has been speculated that the seasonality of the boundaries. In the South Atlantic waters off Brazil, lo" 
448 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996 
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