Ocean-Atmospheric Variability in the Pan-Atlantic basin
Youichi Tanimoto
Tokyo Metropolitan University
Also affiliated with Frontier Research System for Global Change
Ocean and atmosphere variability is investigated over the whole Atlantic basin from Greenland to the Southern Ocean. In the tropics, sea surface temperature (SST) variations are separated into two time scales : decadal (8-16 years) and interannual (-5 years) time scales. A strong cross-equatorial gradient mode dominates decadal SST anomalies with action centers of opposing polarities at 15N and 15S, while the interannual variations show the same polarity on both sides of the equator. Sea level pressure (SLP) regressions onto the cross-equatorial gradient index reveal extratropical teleconnections associated with the North Atlantic Oscillation (NAO) and to the South Atlantic. At the same time, a Pan-Atlantic spatial pattern is also found in SST regressions. Furthermore, lagged regressions of SLP on the cross-equatorial SST gradient index shows the extratropical decadal oscillation that is out of phase between hemispheres. This implies an extratropical forcing that could excite the tropical Atlantic variability.
