This study analyzed how the impacts of major teleconnection patterns on December mean temperature in Korea have been changed during the period before and after the regime shift of 1986 for the last 61 years from 1958 to 2018. During the period before the regime shift, the teleconnection patterns originating from the North Atlantic mainly affected the temperature variability in Korea, but its influence almost disappeared after the regime shift. On the other hand, the Arctic Oscillation (AO) and warm Arctic and cold Eurasia (WACE) patterns played a more important role in the temperature variability in Korea after the regime shift. Regression analysis showed that the AO could explain about 12% of the total temperature variability before the regime shift, but about 22% after the regime shift. WACE pattern also explained about 4% before the regime shift, but after the regime shift, the importance increased by about 4.5 times to 18%. On the other hand, East Atlantic pattern (EA) and North Atlantic Oscillation (NAO), which are east-west teleconnection patterns, explained 27% and 11%, respectively, before the regime shift, but had little influence within 3% after the regime shift. This means that the influence of east-west teleconnection patterns disappeared after the regime shift, and teleconnection patterns by the Arctic Circle became more important.

The Korean Peninsula has experienced regime shift (RS) in winter temperature since the mid-1980s. After the RS, monthly mean temperature significantly increased by 1.05°C in December with 95% confidence level, 1.36°C in January with 99% confidence level, and 1.60°C in February with 99% confidence level, respectively. Interestingly there is no RS in warm winter with 95% confidence level while there is a clear RS in cold winter with 99% confidence level, especially in December and January (DJ), indicating that the RS of winter temperature is mainly due to an abrupt temperature shift in December and January after the RS. Composite analysis suggests that abrupt shift in January after the RS is related to the reduction in sea level pressure (SLP) between Siberian high and Aleutian low, leading to anomalous southerly. However, abrupt shift in December is closely related to the propagation of Rossby wave spanning from the weakening of Ural high to negative anomaly over the North Pacific via high pressure anomaly over the Korean Peninsula, leading to adiabatic heating. Wave activity flux analysis suggests that the abrupt shift of DJ and the associated high pressure anomaly over the Korean Peninsula is induced by the propagation of Rossby wave spanning from North Atlantic Ocean to the Korean Peninsula via the Arctic, especially in cold winter.