Driving Mechanisms of an Extreme Winter Sea Ice Breakup Event in the Beaufort Sea

International audienceArctic sea ice is thinning (Meier, 2017) in conjunction with the decrease in the area covered by thick multiyear ice (MYI) (Kwok, 2018), which is replaced by thinner first-year ice (FYI) that is more mobile and less dynamically stable (Rampal et al., 2009; J. Zhang et al., 2012). This makes the ice cover more vulnerable to intense winds breaking up the sea ice. In the Beaufort Sea in particular, the loss of MYI may contribute to the earlier onset of the melt season in recent years (Johnson & Eicken, 2016). When sea ice breaks up, it exposes the underlying warmer ocean within narrow, linear openings in the ice cover known as leads. This has important consequences for air-sea exchange, ocean eddy generation and dynamics, sea ice production, and Arctic Ocean properties in general (Cohanim et al., 2021; Graham et al., 2019; Nguyen et al., 2009), especially during the winter months when heat fluxes over sea ice are generally small (Andreas & Cash, 1999). In addition, breakup in winter weakens the ice cover, potentially preconditioning the minimum ice extent in summer (Y. Zhang et al., 2018; Babb et al., 2019) and thus creating a positive feedback to Arctic amplification (Dai et al., 2019). Therefore, extreme breakup events are of crucial interest for understanding the seasonal and long-term evolution of Arctic sea ice, which in turn affect weather, ecosystems, and local communities in polar regions and beyond (Forbes et al., 2016; Vihma, 2014)