Short term variability of the upwelling near Cabo Frio (Brazil)

The region of the Brazilian coast known as Cabo Frio, at approximately 23 S, marks an abrupt change in the coastline orientation from N-S to E-W. The continental shelf in that region is relatively narrow, with the 50 m isobath located close to the shoreline. The predominant winds in the region are from the northeast, with a strong modulation by sea-breeze. Cabo Frio owes its name to the frequent observations of relatively low surface temperature which are believed to be related to upwelling. Another possibly related feature observed in the region are the cyclonic vortices generated by the Brazil Current, which are associated with the change in the coastline orientation. These vortices are believed to enhance the pumping of South Atlantic Central Water onto the inner continental shelf.

Here we present results from an analysis of several time series hydrographic stations at fixed locations near Cabo Frio, of synoptic charts and of satellite derived sea surface temperature. The preliminary results reveal large changes of the vertical stratification in response to rapid variations in the forcing systems. The data suggest that short term variability of the Cabo Frio upwelling is induced by three main factors: the large-scale wind distribution, the sea-breeze and the cyclonic meanders of the Brazil Current. In order to verify these hypotheses, we are presently analyzing historical hydrographic, meteorological and SST data sets.