The Relationship Between Snow Cover And Arctic Sea Ice In The Western Qinghai-Tibet Plateau In Winter And Its Mechanism

In the context of global warming,the cyosphere is undergoing significant climate impact.The Arctic sea ice and the snow cover of the Tibetan Plateau(hereinafter referred to as the "TP")has decreased.However,in the western part of the TP,the glaciers have expanded slightly in the past two decades,and the high altitude snow duration has not decreased widely.This suggests that the cryosphere in the Arctic and western TP has completely different climate responses.Whether the western TP snow variation is related to the Arctic sea ice changes is a problem worthy of in-depth discussion and research in dealing with global warming.This paper used satellite-observed snow and sea ice concentration data,reanalysis data and atmospheric circulation model to explore the interannual and decadal relationship between winter Arctic sea ice and snow depth in the western TP with the various conventional statistical analysis methods,and analyzed the physical mechanism of Arctic sea ice influencing the western TP snow depth through dynamic diagnosis and numerical simulation.The main conclusions are as follows:(1)The western TP snow depth have a significant interannual relationship with Arctic sea ice.The increase in the central and western TP snow depth corresponds to the increase in the Barents sea ice and the decrease in the Labrador sea ice.The relationship between snow depth and Arctic sea ice is closely linked by two North Atlantic Oscillation(NAO)circulation patterns.When the southern center of NAO in the middle troposphere is located near Western Europe,the negative phase of NAO stimulate the southern branch Rossby wave train that propagates from Western Europe to the north side of the Arabian Sea,deepening geopotential height on the southwest side of the TP,forming a cyclonic circulation anomaly,leading to the southerly water vapor transportation,which promotes the snowfall and snow accumulation over the central and western TP.When the southern center of NAO in the middle troposphere is located over the Atlantic Ocean,the negative NAO phase mainly affects the central and western TP snow depth by the north branch Rossby wave propagating along the Eurasian continent.(2)The increased Barents Sea ice and decreased Labrador sea ice are likely to affect NAO,promoting the influence of NAO on the central and western TP snow depth through the south branch Rossby wave.The effect of sea ice is mainly formed by the decrease of Labrador sea ice.The increased Barents Sea ice can adjust the propagation path of the Rossby wave formed by the decreased Labrador sea ice.The sea surface temperature anomaly of the mid-latitudes Atlantic Ocean is conducive to the influence of NAO on the central and western TP snow depth through the south branch Rossby wave,while that of low and middle latitudes Atlantic Ocean is benefit for the influence of NAO on the central and western TP snow depth through the north branch Rossby wave.(3)The decadal variability of the western TP snow depth is significantly related to the Arctic sea ice.Snow depth decreased before 1990 and increased slightly after 1990.The decadal variation of snow depth is mainly caused by the convergence of meridional water vapor flux formed by the cyclonic circulation on the southwest side of the TP during the negative phase of NAO.The decadal influence of NAO on the TP snow depth is regulated by the Aleutian Low.When the change of NAO is in phase with the Aleutian Low,the impact of NAO on the western TP snow depth is more conspicuous.The feedback of Arctic sea ice can strengthen the decadal influence of NAO on the western TP snow depth.(4)The Barents Sea ice can regulate the central and western TP snow through the zonal wind.The increase in Barents Sea ice weakens the heat transferring from the ocean to the atmosphere,reducing the lower atmosphere temperature,increasing the meridional temperature gradient of Eurasia,strengthening the polar-front jet,and stimulating the Rossby wave train propagating from the Arctic to the TP,forming a anticyclone circulation on the northern side of the TP and a southeast wind climbing to the central and western TP,which contributes to snowfall and snow accumulation over the central and western TP.The seasonal lag effect of the Barents Sea ice can lead to a spring WP circulation response through the temperature advection of the meridional wind,which in turn affects the spring East Asia precipitation,and the TP snow can be used as a climate predictor indicating this seasonal lag effect.