[A-CG37] Science in the Arctic Region

[ACG37-P06] Did an Arctic sea-ice hole cause hemispheric extreme cold winter in 2017/18?

*Keisuke Ota¹, Yoshihiro Tachibana¹, Kensuke K. Komatsu¹, Alexeev A. Vladimir², Cai Lei², Yuta Ando¹ (1.Graduate School of Bioresources, Mie University, 2.International Arctic Research Center, University of Alaska Fairbanks)

Keywords:Chukchi Sea, Sea-ice

While unprecedented cold weather characterized the American and Asian winter of 2017/18, the Pacific side of the Arctic experienced largely ice-free ocean, referred to as a “sea-ice hole.” The jet stream dividing cold Arctic air from warm persistently meandered northward with intrusion into the sea-ice hole. Large southward streams over Asia and America were also persistent, allowing cold air to spread there. We hypothesise that the sea-ice hole and Pacific atmospheric rivers were responsible for the cold winter, using data analyses and numerical experiments. We argue that the presence of the sea-ice hole resulted in formation of atmospheric rivers that penetrated into the Arctic with anomalous south winds toward the sea-ice hole, which led to more warm water injected into the sea-ice hole by the wind-driven current through Bering Strait. Poleward propagation of the atmospheric rivers made upper air warm, leading to their upgliding, which further heated the overlying air, causing poleward jet meanders. As a part of the response the jet meandered southward over Asia and North America, resulting in cold intrusions. This winter may be the first year when the sea-ice hole shifted the dynamics of hemispheric climate to the new state, with potential for self-sustainability.