Sea-Level as a Driver of the Arctic Sea-Ice and Climate

The integration of the Arctic Ocean in the global climate system implies interactions with lower latitudes through atmospheric circulation and water mass exchanges in the ocean. The gateways to the Arctic Ocean are thus determinant and the shallow Bering Strait linking the Pacific and Arctic deserves a special attention as it experienced on and off connections forced by sea level changes. Under high sea-level, Poleward heat transfer and freshwater fluxes from the Pacific directly impact Arctic sea-ice and freshwater budget, thus the North Atlantic thermohaline circulation. In addition, sea level determines the status of the Arctic shelves, submerged or not, which plays a role on sea-ice production, as well as on the latent heat from Atlantic waters flowing northward through Fram Strait and the Barents Sea. Hence, under full interglacial conditions, high sea-level results in the connection of the Arctic basin with the Pacific and submergence of shelves, which may modify the global heat budget. The timing and quantification of sea-level impact on the Arctic Ocean and subarctic seas during older interglacials is not easily reconstructed from sediment, but radiocarbon-based chronologies and proxy-data covering the present interglacial do provide robust information on these features. For example, micropaleontological and geochemical records from the Chukchi Sea show progressive warming in surface water accompanying the increased 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 southeastern Arctic (de Vernal et al. PNAS 2020), and with paleoceanographical changes at the eastern gateway of the Fram Strait, where cooling is recorded from early to late Holocene. Hence, we may propose that increased freshwater inflow from the Pacific through the Arctic and enhanced sea ice formation rates from early to late Holocene, both linked to sea-level rise, accounted for freshwater-meltwater export to the northern North Atlantic resulting in the general cooling trend, which is not fully explained by atmospheric CO2 and insolation changes (Liu et al. PNAS 2014). In order to test the above-mentioned hypothesis, special attention needs to be paid the paleoceanography of both Pacific and Atlantic Gateways to the Arctic Ocean.