Interdecadal Changes of the Relationship Between Late Autumn Sea Surface Temperature in North Atlantic and Surface Air Temperature in Northwestern Eurasia: Characteristics and Mechanism

This study uses ERA5 reanalysis data from 1940 to 2022 to investigate the decadal variation characteristics and causes of the correlation between sea surface temperature (SST) anomalies in North Atlantic and surface air temperature in northwestern Eurasia (NWESAT). The research reveals that the correlation between North Atlantic SST and NWESAT is significant during two high epochs, 1940—1981 and 2001—2008. During these epochs, the SST anomalies associated with NWESAT exhibit a horseshoe pattern. In contrast, during low epochs, the SST anomalies display a tripole pattern. Further analysis of the reasons behind the changes in correlation shows that, in the high epoch, SST anomalies lead NWESAT, with higher sea surface temperatures north of the Gulf Stream, creating better moisture conditions, more precipitation, and stronger upper-level diabatic heating. Additionally, there is more active eddy-mediated processes above the Gulf Stream, with stronger wave sources in the upper atmosphere to the north of the current, promoting the development of upper-level wave trains. In low epoch, the SST anomalies mainly exhibit a tripole pattern, with lower sea surface temperatures north of the Gulf Stream, weakening the ocean influence on the atmosphere and causing a lag in SST anomalies relative to NWESAT. Therefore, the decadal variations in the correlation between North Atlantic SST anomalies and NWESAT are primarily driven by differences in SST anomaly patterns and their modulation of atmospheric wave trains over time.