Sea level and the Bering Strait gateway as determinant parameters in the ocean dynamics as illustrated from pan-Arctic Holocene records

The shallow (~ 50 m deep) Bering Strait, which is the unique gateway linking the Pacific Ocean to the Arctic Ocean, deserves special attention as sea-level changes modify considerably the exchanges between the two oceans. Under high sea level, poleward heat transfer and freshwater fluxes from the Pacific impact the Arctic freshwater budget and sea ice distribution. Furthermore, sea level determines the status of the Arctic shelves, submerged or not, which plays a role in sea-ice production, as well as in the latent heat from Atlantic waters flowing northward through Fram Strait and the Barents Sea. Hence, high sea levels result in the connection of the Arctic basin with the Pacific, which modifies the Arctic freshwater and heat budgets and leads to the submergence of shelves, thus the potential development of sea-ice factories. The impacts of sea-level on the Arctic Ocean and subarctic seas are not easily reconstructed from sedimentary records, but radiocarbon-based chronologies and proxy-data covering the present interglacial provide useful information. For example, micropaleontological and geochemical records from the Chukchi Sea show progressive warming in surface water accompanying the increase of Pacific flux during the Holocene, until sea-level reached its present-day limit at ~ 4 ka BP. This contrasts with a trend towards perennial sea-ice cover in the southeastern Arctic and with changes at the eastern gateway of the Fram Strait, where cooling is recorded from early to late Holocene. Hence, we hypothesize that increased freshwater inflow from the Pacific into the Arctic together with enhanced sea-ice formation rates, both linked to sea-level rise, may have played a role in the general cooling trend culminating during the late Holocene.