Ocean surface processes on the southern Brazilian shelf: characterization and seasonal variability

Abstract

The oceanographic environment in the southern Brazilian shelf was investigated using maritime weather reports from the U.S. National Climatic Center and data from three hydrographic cruises. The circulation in the area shows a clear seasonal pattern in which the interaction between wind forcing, geostrophic circulation and meso-scale variability of the Brazil Current produce southward and offshore flow over the shelf during summer, and northward and onshore flow during winter. The interaction between eddy-induced upwelling and wind-generated transport in summer and winter results in enhanced upwelling and a strong bottom intrusion of SACW on the shelf in summer, whereas in winter the upwelling is restricted to the shelf break. Thus, the combination of the aforementioned processes produces a complex and highly dynamic hydrographic system with a high degree of seasonal variation in both direction of flow and water mass composition.