the 22nd Pacific−Asian Marginal Seas meeting (PAMS)

Recent rapid declines in sea ice have been observed in the Bering Sea and adjacent Arctic regions, with particularly pronounced reductions occurring in late summer (September). As a key gateway connecting the Pacific Ocean and the Arctic Ocean, the Bering Sea plays a critical role in the Arctic climate system; thus, quantitatively understanding sea ice variability in this region is essential for improving Arctic climate projections and broader climate predictability. In this study, we apply a simplified stochastic climate model based on the statistical framework of Moon and Wettlaufer (2017) to estimate seasonal stability a(t), noise amplitude N(t), and long-term forcing f, and to investigate sea ice variability in the Bering Sea. Our results reveal pronounced instability along the marginal ice zone of the Bering Sea and the adjacent Arctic during summer to late summer. While the sea ice–albedo feedback driven by incoming solar radiation dominates during summer, continued sea ice decline in late summer occurs despite reduced solar forcing. This delayed response suggests the importance of oceanic processes, particularly the release of stored ocean heat and changes in ocean stratification. In particular, strong density gradients between dense Bering Sea waters and the low-density freshwater layer formed by sea ice melt induce baroclinic instability. This process facilitates enhanced ocean heat transport, which in turn accelerates basal sea ice melt. Recent trends indicate that both density contrasts and associated instabilities are intensifying, implying further amplification of sea ice loss in this region. These findings provide important physical insights for assessing the seasonal accessibility and operational stability of Arctic shipping routes.

seasonality,stability,sea ice albedo feedback,ocean eddies,ocean density