Delayed impacts of the Bering Strait oceanic heat flux on Arctic sea ice: One-third of summer/fall sea-ice variability in the following year explained by in situ data

Changing Arctic sea ice influences not only the Arctic and sub-Arctic but also the lower latitudes via disruption of weather patterns. Understanding the many drivers of sea-ice change is essential to predicting future sea ice. Oceanic heat entering the Arctic from the Pacific (all of which enters via the Bering Strait) has been recognized as one such important influence on Arctic sea ice, but prior studies have focused only on the same-year influence of this oceanic heat. Using estimates of total annual flux of Bering Strait oceanic heat from year-round in situ Bering Strait mooring measurements (1991–2024), we discovered a significant correlation (r = −0.58) between this annual heat flux and the whole-Arctic September minimum sea-ice extent in the following year. This correlation suggests that the Bering Strait inflow has a significant lagged effect on Arctic sea ice, explaining about one-third (r2) of the summer sea-ice variability. This correlation is widespread in the western Arctic, particularly the Russian shelf seas (regions important for Arctic shipping), where warm Pacific waters are usually found as a subsurface temperature maximum. As Pacific waters are near freezing when they leave the Arctic, this lagged correlation most likely arises from upward transfer of Pacific water heat thinning sea ice through winter, making it more vulnerable to melt-back the following spring. The regions of influence are consistent with plausible advection times for Pacific waters. Investigations showed that having Bering Strait oceanic heat information only until August (the duration compatible with annual mooring servicing in summer/fall) provides an equally good correlation, raising the intriguing possibility of an in situ observation-based prediction scheme for sea ice in the following year. These results highlight the importance of continued Bering Strait in situ measurements and the necessity of accurate simulation of Bering Strait fluxes in modeling studies of Arctic sea-ice change.