Increasing and Intensifying of Extreme Arctic Anticyclonic Circulation and Its Linkage with the Warm Arctic-Cold Continents Pattern

This paper defines the positive anomaly of 500 hPa geopotential height north of 65°N as Arctic anticyclonic circulation (AAC). Using the percentile threshold (95^th) method, 641 days of extreme AAC (EAAC) events are identified. EAAC occurs most frequently and intensely in winter (December to March), showing a significant upward trend, with occurrence days decreasing in the Pacific sector, the Atlantic sector, and the Eurasian sector of the Arctic. The strengthening of EAAC in these sectors and its linkage with the "warm Arctic-cold continents" (WACC) pattern are associated with abnormal upper-level jet stream changes modulating Rossby wave development at middle-high latitudes. In the Pacific sector, weakened zonal winds at the East Asian-North Pacific jet exit enhance the Alaska ridges, leading to "warm Arctic" conditions; cold advection from cut-off lows forms "cold continents". In the North Atlantic, asymmetric zonal wind changes at the jet exit increase cyclonic vorticity, strengthening the Greenland ridges and inducing EAAC and WACC. In Eurasia, a northward-shifted westerly jet and anomalous easterlies promote Rossby wave propagation, enhancing cyclonic vorticity and shifting the polar vortex, thus strengthening EAAC and forming WACC. This study offers a new perspective on Arctic-midlatitude climate linkages.