An interdecadal climate cycle in the South Atlantic and its links to other ocean basins

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Abstract
A singular value decomposition analysis and a combined complex empirical orthogonal function analysis are performed on 80 years of monthly sea surface temperature (SST) and sea level pressure (SLP) data from the South Atlantic region. The analyses reveal the existence of interdecadal fluctuations in the coupled atmosphere‐ocean system with a period of around 20 years. The SST anomalies are observed to propagate anticyclonically around the South Atlantic basin following the subtropical gyre circulation. At the same time, a westward propagation of SLP anomalies across the basin generates changes in the atmospheric circulation that appear to reinforce such SST anomalies through anomalous exchanges of heat. It is thus proposed that the dominant physical processes involved in this interdecadal cycle include the horizontal advection of heat by the ocean currents and changes in the atmosphere‐ocean heat fluxes through local air‐sea interactions. The global SST and SLP patterns that accompany the different phases of the South Atlantic cycle are also presented. They show similarities with other well‐known interdecadal signals observed by several investigators in other ocean basins (e.g., the low‐frequency part of the North Atlantic Oscillation). This suggests that the South Atlantic signal described in this study may be a regional aspect of global interdecadal variability.