Abstract

The Beaufort Sea has experienced a significant decline in sea ice, with thinner first-year ice replacing thicker multi-year ice. This transition makes the ice cover weaker and more mobile, making it more vulnerable to breakup during winter. Using a coupled ocean-sea-ice model, we investigated the impact of these changes on sea-ice breakup events and lead formation from 2000 to 2018. The simulation shows an increasing trend in the Beaufort Sea lead area fraction during winter, with a pronounced transition around 2007. A high lead area fraction in winter promotes a significant growth of new, thin ice within the Beaufort region while also leading to enhanced sea ice transport out of the area. The export offsets ice growth, resulting in negative volume anomalies and preconditioning a thinner and weaker ice pack at the end of the cool season. Our results indicate that large breakup events may become more frequent as the sea-ice cover thins and that such events only became common after 2007. This result highlights the need to represent these processes in global-scale climate models to improve projections of the Arctic.