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.