Siberian High Enhances Winter Arctic Warming Over The Past Decade

Using the monthly mean dataset of ERA-Interim, JRA-25 and sea ice concentration(SIC) data from Hadley center, the features of the temporal evolution of winter Arctic surface air temperature(SAT) and the roles of different factors related to the rising Arctic temperature are analyzed. Finally a mechanism that the mid-latitude circulation could influence the winter Arctic SAT is suggested. The main conclusions are summarized as follows:(1) During the past decades, the Arctic surface air temperature(SAT) in autumn has been increasing steadily until recent years. But in winter, instead of a linear trend, the Arctic SAT shows an abrupt change which occurred in 2004. During the years from 1979 to 2003, the first principle component(PC1) of winter Arctic SAT keeps stable and no significant increasing trend is detected. However, the PC1 changed abruptly from the negative phase to the positive phase in the winter of 2004.(2) The variation of SIC significantly correlates with PC1 of the winter Arctic SAT. But as we further investigate the variation of the surface heat flux, no corresponding abrupt change is found, which indicates that the changing Arctic sea ice and related surface heat flux is not the main reason why the winter Arctic SAT changes abruptly.(3) Previous studies have proved that in winter, the longwave radiation from cloud favors a warmer Arctic. However, the increasing SAT near Barents Sea is accompanied by a significant decline in cloud cover. The results of correlation analysis and regression analysis shows significant negative correlation between the PC1 of SAT and cloud cover, which implies that the cloud cover is not responsible for the abrupt change of winter Arctic SAT.(4) The enhanced Siberian high may contributed to the abrupt change of SAT because the PC1 significantly correlates with the SLP variation in the north Eurasian continent, and the atmospheric circulation anomaly related to the Siberian high from 2004 to 2013 favors a warmer Arctic. The warm advection to the west of the enhanced Siberian high plays a key role in warming the Arctic.