The role of Arctic gateways on sea ice and circulation in the Arctic and North Atlantic Oceans: a sensitivity study with an ocean-sea-ice model

Abstract

The impact of changes in volume, heat and freshwater fluxes through Arctic gateways on sea ice, circulation and fresh water and heat contents of the Arctic and North Atlantic Oceans is not fully understood. To explore the role played by each gateway, we use a regional sea-ice ocean general circulation model with a fixed atmospheric forcing. We run sensitivity simulations with combinations of Bering Strait (BS) and Canadian Arctic Archipelago (CAA) open and closed inspired by paleogeography of the Arctic. We show that fluxes through BS influence the Arctic, Atlantic and Nordic Seas while the impact of the CAA is more dominant in the Nordic Seas. In the experiments with BS closed, there is a change in the surface circulation of the Arctic with a weakening of the Beaufort Gyre by about thirty percent. As a consequence, the Siberian river discharge is spread offshore to the west, rather than being directly advected away by the Transpolar Drift. This results in a decrease of salinity in the upper 50 m across much of the central Arctic and East Siberian and Chukchi Seas. We also find an increase in stratification between the surface and subsurface layers after closure of BS. Moreover, closure of the BS results in an upward shift of the relatively warm waters lying between 50 and 120 m, as well as a reorganization of heat storage and transport. Consequently, more heat is kept in the upper layers of the Arctic Ocean, thus increasing the heat content in the upper 50 m and leading to a thinner sea ice cover. The CAA closing has a large impact on sea ice, temperature and salinity in the subarctic North Atlantic with opposite responses in the Greenland-Iceland-Norwegian Seas and Baffin Bay. It is also found that CAA being open or closed strongly controls the sea ice export through the Fram Strait. In all our experiments, the changes in temperature and salinity of the Barents and Kara Seas, and in fluxes through Barents Sea Opening are relatively small, suggesting that they are likely controlled by the atmospheric processes. Our results demonstrate the need to take into consideration the fluxes through the Arctic gateways when addressing the ocean and climate changes during deglaciations as well as for predictions of future climate.