Investigation of the Brazil Current front variability from altimeter data

Abstract

The southwestern Atlantic Ocean is characterized by the confluence of the Brazil and Malvinas Currents, which form very strong surface and subsurface fronts that can be detected from hydrographic and remote sensing observations. Three data sets, consisting of TOPEX/Poseidon‐derived sea height anomalies, the climatologically derived depth of the 10°C isotherm, and reduced gravity, are used in conjunction with a two‐layer dynamical ocean scheme to monitor the Brazil Current front and to investigate its variability during a 6 year period (1993–1998). Results reveal that the fronts exhibit motions that are larger zonally than meridionally, showing strong interannual variability with annual mean amplitudes that range from 1° to 6°. The annual and semiannual components account for more than 75% of the variability of the frontal oscillations. In the annual cycle the frontal motions appear to be related closely to fluctuations in the baroclinic transport of the Brazil Current and are only influenced by the Malvinas Current when the Brazil Current transport is very small.