北大西洋海表温度年际变异三极子的演变特征和形成过程OA

Based on observational and reanalysis data from 1980 to 2022,this study investigates evolution features and formation processes of the North Atlantic Sea Surface Temperature(SST)interannual Anomaly Tripole(NAT)through EOF and regression analyses and SST tendency diagnosis.Results obtained are as follows.NAT exhibits to be the dominant mode of interannual variation of the North Atlantic sea surface temperatures.It emerges in the early winter,matures in spring,and decays in autumn.There is a significant correlation between the preceding winter North Atlantic Oscillation(NAO)and the spring NAT,in which a positive phase of NAO corresponds to negative(positive)SST anomalies in the subpolar and subtropical(midlatitude)North Atlantic.NAO tends to drive NAT through local dynamical and thermodynamic processes in the upper ocean in which dominant processes are distinct in three key regions of the tripole.Negative SST anomalies in the subpolar region are primarily driven by anomalous cold advection induced by southward Ekman flow anomalies.Positive SST anomalies in the midlatitude region are generated jointly by anomalous warm advection due to northward Ekman flow anomalies and by decreased upward latent heat flux anomalies due to weakened surface winds.Negative SST anomalies in the subtropical region are mainly attributed to increased upward latent heat flux resulting from enhanced surface wind speeds.