Interannual to decadal changes in the western South Atlantic's surface circulation

[1] A combination of surface drifters and altimetry is used to analyze the seasonal to interannual variability of the surface velocity field in the Brazil-Malvinas confluence of the western South Atlantic Ocean. Longer-term changes are inferred from wind and sea surface temperature fields. During the period October 1992 to December 2007, a southward shift of −0.6 to −0.9° decade−1 is found in the confluence latitude of the Brazil and Malvinas currents. A comparable trend is found in the latitude of the maximum wind stress curl averaged across the South Atlantic basin, allowing a proxy for the confluence latitude to be calculated for the prealtimeter time period. This longer time series suggests that the recent trend may be part of a longer-term oscillation, which has returned to values last sustained in the early 1980s. This variation does not appear to be related to the multidecadal trend in the Southern Annular Mode, but instead is inversely related to long-term variations in the sea surface temperature anomaly in the Agulhas-Benguela pathway of the eastern South Atlantic subtropical basin.