Atmospheric Precursors of and Response to Anomalous Arctic Sea Ice in CMIP5 Models

(整期优先)网络出版时间:2018-01-11
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Thisstudyexaminespre-industrialcontrolsimulationsfromCMIP5climatemodelsinanefforttobetterunderstandthecomplexrelationshipsbetweenArcticseaiceandthestratosphere,andbetweenArcticseaiceandcoldwintertemperaturesoverEurasia.WepresentnormalizedregressionsofArcticsea-iceareaagainstseveralatmosphericvariablesatextendedleadandlagtimes.Statisticallysignificantregressionsarefoundatleadsandlags,suggestingbothatmosphericprecursorsof,andresponsesto,lowseaice;butgenerally,theregressionsarestrongerwhentheatmosphereleadsseaice,includingaweakerpolarstratosphericvortexindicatedbypositivepolarcapheightanomalies.Significantpositivemidlatitudeeddyheatfluxanomaliesarealsofoundtoprecedelowseaice.Wearguethatlowseaiceandraisedpolarcapheightarebotharesponsetothisenhancedmidlatitudeeddyheatflux.Theso-called"warmArctic,coldcontinents"anomalypatternispresentonetotwomonthsbeforelowseaice,butisabsentinthemonthsfollowinglowseaice,suggestingthattheEurasiancoolingandlowseaicearedrivenbysimilarprocesses.Lastly,ourresultssuggestadependenceonthegeographicregionoflowseaice,withlowBarents-KaraSeaicecorrelatedwithaweakenedpolarstratosphericvortex,whilstlowSeaofOkhotskiceiscorrelatedwithastrengthenedpolarvortex.Overall,theresultssupportanotionthattheseaice,polarstratosphericvortexandEurasiansurfacetemperaturescollectivelyrespondtolarge-scalechangesintroposphericcirculation.