• Thermohaline circulation


An ocean general-circulation model with an orthogonal curvilinear grid is presented, with the grid north pole over Greenland to achieve improved resolution in the Greenland and Labrador Seas. The model is integrated for 4500 years in five different experiments, with open and closed connections to the Arctic via the Bering Strait (BS) and Canadian Archipelago (CA). When the BS and CA connections are open the Atlantic overturning circulation has a realistic strength (20 Sv), whereas there is stronger overturning with either (25–31 Sv) or both (39 Sv) the connections closed due to additional deep-water formation in the Labrador Sea. The volume fluxes across the Greenland–Iceland–Scotland ridge are reasonably close to those observed with the two connections either open or closed. With only the BS closed, low-salinity waters leave the Arctic via the CA, giving a weak East Greenland Current, whereas with only the CA closed deep-water formation in the Nordic Seas is weak due to the passage of excess low-salinity water originating from the Pacific via the BS. The simulations suggest that both the CA and BS connections to the Arctic Influence the North Atlantic circulation. Closing the BS reduces the effective freshwater input to the Arctic, leading to a strong Atlantic overturning circulation. Closing the CA leads to increased salinity in the Labrador Sea, and additional deep-water formation. It is therefore recommended that both these seaways should be represented in ocean general-circulation models. Copyright © 2002 Royal Meteorological Society