Enhanced Impact of Arctic Sea Ice on Asian Cold Extremes: Interannual Variability Driven by ENSO and NAO

Despite ongoing global warming, extreme cold winter events continue to occur, with some winters experiencing more frequent extremes on an interannual scale, impacting densely populated mid-latitude regions. Previous studies have established a close link between Arctic sea ice anomalies and mid-latitude extreme cold events. Our findings reveal that since 2000, two key mechanisms have amplified the interannual variability of Arctic sea ice and its subsequent influence on extreme cold events in Asia. Firstly, accelerated phase transitions of ENSO have intensified the Western North Pacific anticyclone, which excites stronger Rossby waves propagating toward the Arctic. These waves enhance the interannual variability of Arctic sea ice by inducing anomalous anticyclonic circulation over the Arctic, which in turn increases moisture and heat fluxes into the region. Secondly, heightened interannual variability of the North Atlantic Oscillation (NAO) has increased poleward heat and moisture transport into the Arctic, further amplifying sea ice variability on interannual scales. This enhanced Arctic sea ice interannual variability then induces greater atmospheric instability in the Arctic, generating stronger Rossby waves that propagate into mid-latitude Eurasia. Consequently, anomalous anticyclonic circulation and more frequent blocking highs develop over Eurasia, ultimately intensifying the influence of Arctic sea ice on winter cold extremes in Asia.