冬季格陵兰海海冰对春季欧亚大陆西部极端暖事件影响的年代际变化和机理OA

Since the early 21st century,the Arctic climate system has undergone profound changes,including pro-nounced warming and rapid declines in sea ice thickness and extent.Concurrently,the frequency,intensity,and persistence of extreme weather events in the mid-to high-latitudes of the Northern Hemisphere have increased.As a key transitional season,spring has exhibited marked warming and a rise in extreme heat events across Eurasia,posing substantial risks to agriculture,ecosystems,and socioeconomic systems.Although previous studies have em-phasized the influence of Arctic sea ice—particularly in the Barents Sea—on mid-to high-latitude atmospheric circulation,the role of sea ice variability in the Greenland Sea remains insufficiently explored.This study examines the interdecadal variability of winter Greenland Sea ice and its impact on subsequent spring extreme heat events o-ver western Eurasia.Specifically,we aim to 1)characterize the interdecadal variations in winter Greenland Sea ice,2)identify changes in its relationship with spring extreme heat events over western Eurasia,3)elucidate the physical mechanisms underlying this teleconnection,and 4)investigate the factors contributing to the strengthened relationship after 2003. We analyze observational and reanalysis datasets spanning 1979-2023,including ERA5 and HadISST.Sta-tistical methods such as correlation,regression,and SVD(singular value decomposition)analyses are employed,with significance assessed using Student's t-tests.To further elucidate the physical mechanisms linking Greenland Sea ice modulates atmospheric circulation,two numerical experiments(SIC_Pos and SIC_Neg)are conducted u-sing the CAM6 model.These experiments impose composite sea ice anomalies representative of high and low sea ice conditions,and the atmospheric responses over the final 45 simulation years are analyzed. Results show that after 2003,the interannual variability of winter Greenland Sea ice concentration weakened,while its correlation with spring extreme heat events across western Eurasia strengthened.SVD analysis reveals that reduced Greenland Sea ice is associated with a dipole pattern of spring extreme heat events,characterized by warming over Europe and cooling over western Siberia,hereafter referred to as the spring extreme heat event(SEHE)pattern.Negative winter sea ice anomalies enhance local atmospheric heating and modify thermal gradi-ents,inducing anomalous vertical circulation with ascent near 65°N and descent near 40°N.These circulation a-nomalies resemble the positive phase of the North Atlantic Oscillation,weakening mid-latitude surface winds over the North Atlantic and promoting warm sea surface temperature anomalies that persist into spring.Concurrently,reduced spring sea ice in the Greenland Sea increases oceanic heat absorption,further amplifying surface warming.The resulting sea surface temperature anomalies excite an eastward-propagating Rossby wave train,es-tablishing a meridional dipole circulation pattern over mid-to high-latitude Eurasia that favors the SEHE pattern.Furthermore,the combined effects of background spring warming over Eurasia and enhanced persistence of sea surface temperature anomalies amplify the response of extreme heat events to Greenland Sea ice variability after 2003. This study highlights the critical role of enhanced sea surface temperature persistence in mediating the influ-ence of Greenland Sea ice anomalies on spring extreme heat events.However,the mechanisms responsible for this enhanced persistence—such as changes in ocean mixed-layer depth,background ocean circulation,and atmospheric internal variability—remain unclear.Further research is needed to determine whether these processes are governed by a common climatic driver or whether reduced sea ice variability initiates sea surface temperature responses that subsequently modulate extreme heat events.