Observed contribution of Barents-Kara sea ice loss to warm Arctic-cold Eurasia anomalies by submonthly processes in winter

Abstract

Abstract The warm Arctic-cold Eurasia (WACE) pattern of surface air temperature anomalies is a prominent feature of the Eurasian climate variations during boreal winter. The interannual WACE anomalies are accompanied by sea ice loss in the Barents-Kara (BK) seas, however, the causality between them remains controversial because of large internal atmospheric variability over subarctic Eurasia in winter. Here we disentangle the contribution of BK sea ice loss to the WACE anomalies based on a statistical decomposition approach. An anticyclonic circulation anomaly over subarctic Eurasia that forces the WACE anomalies is found to reach its peak 3 d prior to BK sea ice loss. After excluding this prior atmospheric forcing signature, the East Asian cooling matures about 15 d later as a result of the weakened moisture transport associated with the enhanced BK downstream ridge and East Asian trough due to BK sea ice loss. The results suggest that BK sea ice loss contributes ∼65% and ∼81% of the WACE-related East Asian cooling and Arctic warming at interannual timescale, respectively, whereas the WACE-related cooling over central Eurasia primarily results from internal atmospheric variability. Such submonthly lagged East Asia cooling caused by BK sea ice loss could be helpful in predicting winter extreme cold events over East Asia.