Relationship Between Meridional Eddy Heat Transfer In The Northern Hemisphere And Decrease Of Arctic Sea Ice

The rapid melting of Arctic sea ice has attracted much attention in recent years.Arctic sea ice has an important impact on the climate in the Arctic and the northern hemisphere,which is a worthy scientific issue.In this study,the interannual and Interdecadal variability of Arctic sea ice are analyzed.The key areas regarding the Interannual variations of Arctic sea ice(referred to as the key areas of Arctic sea ice,henceforth)in winter and summer are analyzed.On this basis,the effect of polar heat transport on Arctic sea ice in winter and summer is revealed.Meanwhile,the relationship between Arctic sea ice and atmospheric circulation in the middle and high latitudes of northern hemisphere during winter and summer is also diagnosed.Sensitivity experiments are designed to examine the effects of the key areas of winter and summer Arctic sea ice on the atmospheric circulation in the northern hemisphere.The main conclusions of this study are as follows:(1)The Arctic sea ice is affected by global warming in summer-autumn,the variation of Arctic sea ice concentration mainly concentrated along the continental margin in the Kara Sea to Beaufort Sea during 1979-2016.The variation of Arctic sea ice concentration in spring-winter is mainly located in the Barents Sea.Sea ice concentration of Okhotsk and the Bering Strait has obvious interdecadal variation in winter and summer.The sea ice concentration of the key area on the Arctic in summer(Kara Sea-Beaufort Sea)and winter(Barents Sea,Okhotsk)has a significant decreasing trend from 2000 to 2016.(2)Meridional eddy heat transfer of lower atmosphere is an key factor that influence the acceleration of sea ice melting in the key area of the Arctic after 2000 in winter and summer.Compared with 1979-2000,the heat transport from the middle latitudes to Arctic is much evident at 850 hPa in winter during 2000-2016,leading to the rapid melting of sea ice.The heat flux transport from southwest of Pacific to Okhotsk is much evident during 2000-2016,which is an important reason to the rapid melting of sea ice.In Bering Strait,the heat flux has an obvious northward transport in summer after 2000,resulting in ice melting over the key areas of Arctic sea.(3)The sea ice concentration in the key area of the Arctic during summer and winter has an obvious impact on the atmospheric circulation,which may change meridional eddy heat transfer in middle and high latitudes of the Northern Hemisphere and influence the temperature of Eurasia.The mean trough and ridge systems deepen(weaken)at 500 hPa in the Northern Hemisphere and polar-front jet weaken(enhance)over Eurasia with the decrease of Sea ice concentration of Barents Sea in winter,thus,the exchange of Meridional eddy heat transfer could enhance(weaken)in middle and high latitudes,the cold air in the polar region is(not)conducive to the transport of southward,which leads to the decrease(increase)of temperature in the Central Asia and Southern Japan;The correlation between sea ice concentration of the Okhotsk and atmospheric general circulation of the northern hemisphere during winter shows that the Arctic and Central Asia as well as the southern region of Japan and Okhotsk both appears the seesaw pattern regarding the temperature distribution.With the sea ice concentration of Khara sea-Beaufort sea decreasing(increasing)in summer,the temperature rises(decrease)in most parts of Eurasia.(4)The atmospheric circulation anomaly in summer can affect autumn sea ice.The autumn sea ice anomaly also has a influence on the winter atmospheric circulation.In the lower(higher)sea ice extent years,the summer temperature rises(decreases)in most parts of the northern hemisphere,low atmospheric circulation in the Arctic are controlled by the dipole circulation(low pressure cyclonic circulation)in summer.The circulation distribution is(conducive)not conducive to the melting of autumn sea ice;In the lower(higher)sea ice extent years,Ural high pressure ridge,Siberian high pressure and the East Asia Trough deepen(weaken),polar-front jet weaken(enhance)over Eurasia.The circulation distribution makes the meridional eddy heat transfer strengthen(weaken)and the cold air in the Arctic is(not)conducive to spread southward,which leads to the decrease(increase)of temperature in Central Asia.(5)The result of Sensitivity experiment indicate that,the increase of sea ice concentration in winter over the Barents Sea leads to the polar-front jet enhance over Eurasia ? Siberia high pressure and the exchange of meridional eddy heat transfer weaken.The circulation distribution is not conducive to the southward transport of cold air,which leads to increase of temperature in Central Asia.With the increase of sea ice concentration in Okhotsk,the circulation distribution is similar with the sensitivity experiment of the Barents Sea.The increase of sea ice concentration in the Khara sea-Beaufort sea areas in summer leads to the deepened of Ural high pressure ridge,the weakened of polar-front jet over Eurasia.The circulation distribution is conducive to southward transport of the cold air,leading to the decrease of temperature in most of Eurasia.