The Southern Ocean as a Source Region for Tropical Atlantic Variability

Abstract

A coupled model of intermediate complexity is used to examine the effect of the Southern Ocean on tropical Atlantic variability. Model experiments with positive surface temperature, freshwater, and wind forcings in the Southern Ocean show an increased advection of polar water into the Atlantic basin, resulting in anomalously cold freshwater in the eastern Atlantic Ocean at 25°S. With time, these anomalies spread northward and away from the coast, into the tropical thermocline. The magnitude of the response increases linearly with the strength of the forcing. The results of these experiments show that southeastern Atlantic Ocean temperature and salinity are particularly sensitive to changes in the Southern Ocean. These findings suggest that this link could be the oceanic branch of a mode of variability linking the Southern and tropical Atlantic Oceans?a possible mechanism for the as-yet-unexplained decadal mode of tropical Atlantic variability.