Summer sea ice in the Northwestern Chukchi Sea observed in 2024 for the first time in 25 years

The Arctic Ocean has seen a profound sea ice loss during the summer, with changes most pronounced in the Western Arctic. This has resulted in the Chukchi Sea, located just north of Bering Strait, being ice-free by the end of summer, i.e. September, since 2000, except during 2024. Here using the ice thickness budget, we investigate the processes responsible for the return of summer sea ice to the region during 2024. We show that an exceptional ice convergence event in February 2024, along with additional events in the winter and spring, resulted in ice thicknesses along the Siberian coast of the Chukchi Sea through the summer months that exceeded values last seen in the region during the late 20th century. The reduced penetration of shortwave radiation through the anomalously thick ice contributed to a delay in melt, contributing to the presence of sea ice in the region during the summer of 2024. We also argue that a thinner and more mobile ice pack contributed to this remarkable return of summer sea ice after a 25-year hiatus, opening the possibility of similar events in the future.