The Low Frequency Variability of the South Atlantic Circulation

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Several recent studies have reported a slow-down of the thermohaline circulation. Although none of them are conclusive, they all consistently point to a similar conclusion: the oceanic circulation is changing. Policymakers, however, face the dilemma that although the reported changes could be the heralded response of the oceans to global warming, they could, as well, be a natural mode of ocean variability. To differentiate natural from anthropogenic changes we need increase our understanding of the factors that control the low-frequency variability of the oceanic circulation. The thermohaline circulation is a global phenomenon and to interpret its variations we need to improve our understanding of how the different basins "communicate" with each, that is, how the variability in a particular region affects the entire system. To interpret the climate-related changes occurring in the North Atlantic, for example, we need to understand the variability of its contiguous basin, the South Atlantic; not only because its heat and salt fluxes are essential for the formation of the North Atlantic deep waters, but also because it is its naturallink with all the other major oceans. In this project scientists from Oregon State University will combine the results of ocean general circulation models with remote and in-situ observation to determine the dominant patterns of low-frequency variability of the South Atlantic circulation. Broader impacts: This study is focused on those aspects of the South Atlantic circulation that are most relevant to the climate system and its broader impacts are related to it. Little is known about the low-frequency variations of the South Atlantic circulation and its interocean exchanges. This dearth of information is of serious concern to the scientific community because the South Atlantic is the only nexus between the North Atlantic and the rest of the world ocean.