The Possible Relationship Between Sea Surface Temperature Anomalies Over The Tropical Pacific And The Arctic Sea Ice And Their Collaborative Effect On EAWM

The possible relationship between sea surface temperature anomalies(SSTA)over the tropical Pacific and Arctic sea ice is researched in the form of synthetic analysis, linear regression and T test from atmospheric circulation and net surface heat flux by using monthly data of HadISST and NCEP/NCAR spanning from 1950 to 2015 .Numerical experiments are also adopted to testify the possible physical mechanism.In consideration of the climatic effect,collaborative influence of tropical Pacific SSTA and Arctic sea ice on East Asian Winter Monsoon(EAWM) are studied as well.Conclusions are as follows:(1)The robust abnormal signal of the ENSO event and the Arctic sea ice is mainly manifested in the summer and autumn during its development. Although winter is the peak phase of ENSO,Arctic sea ice, however, has entered the most stable state in the whole year with the smallest interannual variability. Hence,there are no response signals. During summer and autumn of ENSO development phase ,EP and CP El Nino events have no apparent connection with the Arctic sea ice anomalies. However, strong signals are detected when it happens to La Nina and there are distinctive differences between EP and CP events.(2)Sea ice reduce in Barents/Kara Sea in EP La Nina but increase in East Siberia/Chukchi Sea in CP La Nina during summer and autumn of their development. From the aspects of atmospheric circulation and net surface heat flux,in the occasions of EP La Nina,SST anomalies over the tropical Pacific leads to negative SLP in Barents/Kara Sea by teleconnection wave trains and forms AO-like pattern together with positive SLP in middle latitude.It changes the wind which brings warm advection and southerly anomalies that help to transfer more warm water from North Atlantic,high water vapor content at the same time enhance the income of net surface heat flux and result in the decrease of sea ice in Barents/Kara Sea.In the situation of CP La Nina, East Siberia/Chukchi Sea are dominated by north wind in summer because of a cyclonic circulation in the eastern side,sea ice are transported here from North Pole and thus sea ice concentration increased,effect of net surface heat flux is weak.(3)Numerical simulation results show,CAM5 can reflect the influence of the tropical Pacific SSTA on the atmospheric circulation well When the SST anomalies of EP and CP La Nina are added to the model as the only external forcing source,whether it is EP or CP La Nina event,in the key areas of sea ice change, from low to high, the results of atmospheric circulation and temperature distribution are beneficial to the decrease or increase of sea ice.More important ,the simulation results are very similar to the actual ones.That means the atmospheric circulation anomalies in the key areas of the Arctic sea ice and its vicinity are the result of the SST anomalies in the tropical Pacific ocean.SSTA stimulates the atmospheric teleconnection, changes the atmospheric circulation anomaly in the polar region,forms the circulation form that promotes the increase or decrease of sea ice, and finally leads to the change of sea ice in the key area.(4)Changes in the Barents Sea, Kara sea ice and La Nina events are two important factors affecting the East Asian Winter Monsoon.When the two factors work at the same time, Siberia high gets strengthen and expands eastward,a significant component of the north wind guides the cold air break into the south,enhance the EAWM and cool the east Asian regions in winter. And their synergistic action on the EAWM is greater than two factors work respectively.