Abstract
Ocean and atmosphere variability is investigated over the whole Atlantic basin in a 51-year record of sea surface temperature (SST). In the tropics, SSTs variations are separated into two time scales: decadal (8-16 years) and interannual (<5 years). A strong cross-equatorial gradient mode dominates decadal SST anomalies with centers of action having opposite polarities at 15°N and 15°S, while interannual variations are characterized by SST anomalies of the same polarity throughout the tropics. Sea level pressure (SLP) regressions onto the cross-equatorial gradient index reveal extratropical teleconnections associated with the North Atlantic Oscillation (NAO), and with the South Atlantic. At the same time, a Pan-Atlantic spatial pattern is also found in SST regressions. Lagged regressions of SLP on the cross-equatorial SST gradient index shows the extratropical decadal oscillation that is out of phase between hemispheres. These results suggest that an extratropical forcing could excite the tropical Atlantic variability.
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