Impacts of southern hemisphere westerlies on the Brazil current at 30°s

Abstract

Previous studies have pointed out an intensification of the global western boundary currents induced by changes in the wind-stress curl patterns over the oceans. The Brazil Current (BC) is the western boundary current into the South Atlantic Subtropical Gyre, which flows southwards along the Brazilian coast. A numerical model is used to investigate the response of BC to this change in wind forcing between 1960-2010, across 30°S. The results found here support the increasing trend noticed in the wind-stress curl and a poleward migration of the South Hemisphere westerlies in the past decades. The residual transport of BC at 30°S is composed by its southward main flow and the northward branch of a recirculation cell (Rec) east of the BC. Both the BC and Rec transports showed a decrease trend of 0.10 Sv dec-1 and 0.28 Sv dec-1, respectively. It suggests a southward migration of Rec in response to changes in the westerlies. The results also indicate a relative intensification in the western boundary transport and a strengthening in the South Atlantic Subtropical Gyre.