SIMULATION OF NORTH-ATLANTIC DECADAL MULTIDECADAL WINTER SST ANOMALIES DRIVEN BY BASIN-SCALE ATMOSPHERIC CIRCULATION ANOMALIES/

The North Atlantic winter sea surface temperature anomaly (T-sa) respo nse to anomalous surface atmospheric circulation anomalies that vary o ver decadal and short-term inter-decadal periods is simulated for 1950 through 1992. Anomalous ocean variability is driven by adding monthly GOADS-derived anomalous fields of vector wind stress and wind speed t o che climatological annual cycle forcing. A simple model is derived r elating winter T-sa to the integrated atmospheric forcing present earl ier in time that is responsible fdr its existence. The basin-scale str ucture of forced winter T-sa patterns depends on the structure of the atmospheric forcing along with regional differences in the dominant mi xed layer processes that generate T-sa For example, when the atmospher ic subtropical high and subpolar low pressure systems are simultaneous ly strong, enhanced flow around, and baroclinic adjustments within, th e subtropical gyre results in anomalously warm water in the Gulf Strea m region off the U.S. East Coast. At the same time, however the open o cean generally cools because the westerlies and trades are anomalously strong. By analyzing T-sa variability not driven by the atmosphere,an anomalously cold decade is identified characterized by rapid onset an d termination that both occur within one year. The onset during 1968 c oincides with the appearance of the great salinity anomaly, while the termination during 1977 coincides with an abrupt Northern Hemisphere c limate shift that is particularly evident in the Pacific.