The influence of the Brazil and Malvinas Currents on the Southwestern Atlantic Shelf circulation

R P Matano,A R Piola,E D Palma

doi:10.5194/os-6-983-2010

Abstract

Abstract. The oceanic circulation over the southwestern Atlantic shelf is influenced by large tidal amplitudes, substantial freshwater discharges, high wind speeds and – most importantly – by its proximity to two of the largest western boundary currents of the world ocean: the Brazil and Malvinas currents. This review article aims to discriminate the dynamical processes controlling the interaction between this extensive shelf region and the deep-ocean. The discussion is focused on two broad regions: the South Brazil Bight to the north, and Patagonia to the south. The exchanges between the Brazil Current and the South Brazil Bight are characterized by the intermittent development of eddies and meanders of the Brazil Current at the shelfbreak. However, it is argued that this is not the only – nor the most important – influence of the Brazil Current on the shelf. Numerical simulations show that the thermohaline structure of the South Brazil Bight can be entirely ascribed to steady state, bottom boundary layer interactions between the shelf and the Brazil Current. The Malvinas Current does not show the development of eddies and meanders, but its influence on the Patagonian shelf is not less important. Models and observations indicate that the Malvinas Current not only controls the shelfbreak dynamics and cross-shelf exchanges but also influences the circulation in the shelf's interior.

Highlights

The southwestern Atlantic shelf extends from Cape Frio, Brazil (∼23◦ S) to Burdwood’s Bank (∼55◦ S) (Fig. 1)
In this article we reviewed the influence of the Brazil Current (BC) and Malvinas Current (MC) on the circulation of the southwestern Atlantic shelf
The influence of the BC is most visible through sporadic onshore intrusions of eddies and meanders, but it has been argued that this is not the only – nor its most important – contribution to the shelf dynamics

Summary

Introduction

The southwestern Atlantic shelf extends from Cape Frio, Brazil (∼23◦ S) to Burdwood’s Bank (∼55◦ S) (Fig. 1). The Malvinas Current (MC) is a swift, barotropic, and narrow branch of the Antarctic Circumpolar Current that flows north along the continental slope of Argentina up to approximately 38◦ S (Matano et al, 1993). The Brazil Current (BC) is a highly baroclinic western boundary current that concentrates the bulk of its volume transport, between 25 and 40 Sv, in the top 500 m of the water column (Piola and Matano, 2001). The collision of these two currents, known as the Brazil/Malvinas Confluence, occurs near the mouth of the La Plata River where it creates a region of intense mesoscale variability

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Conclusion