Several multi-decade simulations have been made with the UCLA atmospheric General Circulation Model (GCM), in which various distributions of sea-surface temperature (SST) are prescribed over the Atlantic Ocean, with climatological values imposed elsewhere. The results suggest that during austral summer, meridional displacements of the Amazonian convergence zone provide a dynamical linkage between interannual fluctuations of SST over the South Atlantic, and the North Atlantic Oscillation (NAO) teleconnection pattern.
Using December-February averages for the period 1960-90, the first mode of covariability between simulated 500-mb geopotential heights over the North Atlantic and Atlantic SSTs accounts for almost 80% of the squared covariance between them. Warm SST anomalies over the South Atlantic are accompanied by a southward shift in the Amazonian convergence zone and the regional Hadley circulation across the equator. At the same time, the North Atlantic subtropical jet is displaced southward. Positive geopotential height anomalies occur over the North Atlantic, with negative ones over Greenland, characteristic of the positive phase of the NAO.
Further higher resolution (2x2.5 degrees) experiments are being made to elucidate the physical mechanisms by which South Atlantic SST anomalies influence the model's South American monsoon, and how variations in the latter affect the simulated wintertime atmospheric circulation over North Atlantic.