Arctic Sea Ice Melting Has Triggered Distinct Interdecadal Transitions since 2000

Abstract This study investigates dominant features of the temporal evolutions of sea ice concentrations (SICs) in the Barents–Kara Seas in autumn and the subsequent winter, as well as their regulating effect on winter atmospheric circulation variations over the Arctic and Eurasia at phasic and interdecadal time scales. Results suggest that SICs in the Barents–Kara Seas both during autumn and the subsequent winter have exhibited a coincident interdecadal reduction since 2004. This interdecadal reduction has produced significant impacts on much of the Northern Hemisphere. In the Arctic, this interdecadal reduction has directly altered the thermal and moisture structure of the lower troposphere, as well as enhanced the hydrological cycle. Its influence on winter atmospheric humidity can extend into the upper troposphere over the Atlantic sector of the Arctic. Over Eurasia, this interdecadal reduction has strengthened short-term pulsation processes of the Siberian high, making the mean intensity of the Siberian high stronger relative to the average over winters from 1979/80 to 2003/04. Meanwhile, it has weakened the winter atmospheric baroclinicity over high latitudes of Eurasia and strengthened the atmospheric baroclinicity over mid- to low latitudes of East Asia and the northwest Pacific. This interdecadal reduction directly led to the occurrence of warm Arctic–cold Eurasia during winters from 2004/05 to 2012/13. Additionally, a notable finding is that the continuously low level of Arctic sea ice has initiated a recent interdecadal transition in winter 1000-hPa temperature since the early 2010s. This alternation has resulted in the emergence of a warm Arctic–warm Eurasia configuration. Implications of these results suggest that Arctic sea ice melting has produced significant effects on the changing climate system across much of Northern Hemisphere during wintertime, particularly at interdecadal time scales. Significance Statement The purpose of this study is to reveal phasic and interdecadal responses of winter atmospheric circulation over the Arctic and Eurasia to Arctic sea ice melting in the Barents–Kara Seas during autumn and the subsequent winter. Our findings suggest that both the interdecadal reduction of Arctic sea ice and the continuously low level of Arctic sea ice have triggered distinct interdecadal transitions in winter atmospheric circulations. Specifically, the persistent low level of Arctic sea ice has resulted in alternating occurrences of warm Arctic–cold Eurasia and warm Arctic–warm Eurasia patterns. These findings hold significant implications for enhancing our understanding of the impacts of Arctic sea ice melting on both the Arctic and midlatitudes of Eurasia.