Evidence for interannual and interdecadal climate variability in the South Atlantic

Abstract

A singular value decomposition (SVD) analysis is used to determine the coupled modes of variability of monthly sea surface temperature (SST) and sea level pressure (SLP) data from the South Atlantic region, for the period 1953–1992. We find that the three leading SVD modes respectively account for 63%, 20% and 6% of the total square covariance. The first mode represents an approximately 15‐year period oscillation in the strength of the subtropical anticyclone, accompanied by fluctuations of a north‐south dipole structure in the SST. It appears to be linked to the global‐scale interdecadal (15‐year) joint mode in SST and SLP recently studied by Mann and Park. The second mode is characterized by east‐west displacements of the anticyclone center, in association with strong 6 to 7‐year period fluctuations of SST off the coast of Africa. The third mode is characterized by north‐south displacements of the anticyclone and 4‐year period fluctuations in the SST in a broad band across the central South Atlantic. This mode is strongly correlated with ENSO.