Abrupt Northern Baffin Bay Autumn Warming and Sea-Ice Loss Since the Turn of the Twenty-First Century

A delay in autumn sea ice formation is an important consequence of Arctic Amplification. Baffin Bay is one such region impacted by delayed ice formation, though spatiotemporal analyses to date have not detailed the evolution and drivers of such autumn ice changes. In this study, we document abrupt Baffin Bay sea ice cover changes in the key transition month of October from 1950 to 2021. The ice cover mean and variance dramatically change from 2001 onward with a transition to largely ice-free conditions in the northeast and thinner ice in the northwest. Ocean model experiments attribute these changes to warming of the Atlantic-origin water (AOW) flowing into northeastern Baffin Bay from the south. Transport and upwelling of this above-freezing AOW has stunted ice formation in this area, while the basin's cyclonic surface current has contributed to reduced cooling and ice formation in the northwestern portion of Baffin Bay.