Sensitivity Of The Boreal Winter Atmospheric Circulation And Eurasian Cold Events To Sea Ice Variation In Autumn And Winter Over Barents Sea

In this study,sensitivity of the boreal winter atmosphere to sea ice anomalies with different amplitudes in autumn and winter over the Barents Sea(BS)is explored with the Community Atmosphere Model 4.0(CAM4).Both the winter mean atmospheric responses and the typical modals at the mid-high latitudes are studied.Based on the above research,the response of Eurasian cold events in early winter to day-to-day Barents Sea ice concentration(SIC)and its relationship with the deep Arctic warming events are discussed.Major results of this thesis are as follows:1)Sea ice loss over the BS in winter can generate advanced anomalous upward turbulent heat flux,which warms and humidifies the local lower atmosphere with the magnitudes and extents consistent with sea ice anomalies.However,the responses of atmospheric circulation and surface air temperature over the Eurasian continent are nonlinear.In addition,the reduction of sea ice over BS in autumn leads to stronger and wider mean temperature and circulation anomalies over the Eurasian continent.2)During winter,the intensity and location of the Siberian High(SH)and the North Atlantic Oscillation(NAO)phases responses to the reduction of Barents Sea ice in different months are different.In early winter,the SH tends to become stronger and shift more eastward,and the opposite is true in late winter.At the same time,with sea ice loss in autumn,the negative phase of NAO(NAO-)occurs more frequently in later winter,but strong NAO-occurs less frequently.3)Barents Sea ice loss may connect with mild continental winter,albeit,contradicts with the cooling trend over Eurasia.The local positive temperature anomalies over BS and the intensity of Eurasian cold events in response to winter SIC variation are more significant than their response to autumn SIC variation.The possible reason is that sea ice loss in winter promotes advanced upward turbulent heat flux.The prescribed daily SIC variation over BS is a result of air-sea interaction,which may act to lock the atmospheric responses in the perturbed region,and thus creating a stationary atmospheric response.However,sea ice loss in autumn promotes additional surface evaporation,which inhibits the upward turbulent heat flux in early winter.Consequently,Eurasian cold events weaken.4)From the perspective of synoptic scale,"Warm Arctic-Cold Eurasian Continent" is closely related to the quasi-stationary state of dipole blocking pattern.The cold anomalies over Eurasia continent are closely related to Arctic deep warm anomalies,which is the result of interaction between the internal variability of the atmosphere and SIC variation.Moreover,local surface warming induced by sea ice loss does not directly link to cold anomaly over Eurasia.