The seasonal circulation of the Eastern Brazilian shelf between 10°S and 16°S: A modelling approach

The Regional Ocean Modelling System (ROMS) with embedded nesting capabilities based on AGRIF, configured with a refined grid (1/36 degrees) and realistic forcings (6-hourly winds and surface fluxes, daily large scale oceanic forcings and tides), was implemented to describe the seasonal circulation within the Eastern Brazilian Shelf (EBS) between 10 degrees S and 16 degrees S and its interaction with the mesoscale dynamics associated with the Western Boundary Currents (WBC) which flow over the slope: the Brazil Current/North Brazil Current-Undercurrent (BC/NBC-NBUC), as well as the contribution of the forcing mechanisms on the generation of the shelf/slope currents. The model results show, based on the methodology adopted, that for the northern limit (10 degrees S) the northward flow is the dominant pattern while the southward flow appears as a shallow flow confined to the top 50 m of the water column during the spring/summer seasons. The surface circulation at the inner- and mid-shelves in this region is mostly influenced by the wind forcing, while at the shelf-break the currents are mainly driven by the slope currents during all seasons. In the middle (14 degrees S) and southern (16 degrees S) domains, there is an alternate dominance of the southward/northward flows for the first 150 m of the water column, with the dominance of the southward (northward) flow between October-February (March-September) at 14 degrees S. However, the annual net transport in these regions is oriented southwards. On the other hand, in the sub-surface (similar to 150-400 m) the dominance of the northward flow is clear. At 14 degrees S, the inner-shelf circulation is mainly driven by the wind forcing and the mid-shelf circulation is forced by both the wind and the flow over the slope, while the currents at the shelf-break are more influenced by the currents at the slope. Finally, the inner- and mid-shelf currents at 16 degrees S are mainly driven by the wind forcing, while the shelf-break currents present a poor correlation with the wind and a strong influence of the WBC dynamics. (c) 2013 Elsevier Ltd. All rights reserved.