Arctic-subarctic coupled impact on the North Pacific intraseasonal variability

Wednesday, 17 December 2014
Mi-Kyung Sung, Baek-Min Kim and Hyerim Kim, KOPRI Korea Polar Research Institute, Incheon, South Korea
The winter of 2013/2014 brought severe cold events over the northern North America. Here, we analyze the air-sea interaction over the Arctic and subarctic regions that is attributed to provide favorable condition for the outbreak of cold surges. In order to assess the arctic impact on the subarctic and midlatutude regions, we designed an ocean-atmosphere coupled model experiment that is forced by observational sea surface temperature (SST) over the Arctic region and climatological SST elsewhere. When the sea ice over the Chukchi and Beaufort Sea reduced below normal during summer, warm anomaly appeared over the arctic region during late fall to early winter. The atmospheric response to this arctic warming induces anticyclonic circulation, which brings SST warming over the north Pacific subarctic region. The local atmospheric response to the warm SST anomaly acts to reinforce the arctic warming by warm advection, and the ensuing atmospheric response further enhances the SST anomaly. This feedback process between the Arctic and subarctic atmosphere and ocean enables the arctic warming and the anomalous SST over the northern north Pacific to persist and develop until late winter and early spring. It is supposed that the quasi-stationary high over the northwestern North America during 2013 winter that contributed to the development of severe weather events over the adjacent regions was closely linked with the persistent SST anomaly over the northern North Pacific which was resulted from the arctic-subarctic feedback.