Production of dense overflow waters feeding the North Atlantic across the Greenland-Scotland Ridge. Part 1: Evidence for a revised circulation scheme

Abstract

The circulation in the Norwegian and Greenland Seas and the production of dense overflow waters feeding the North Atlantic across the Greenland-Scotland Ridge is reconsidered in light of a more complete set of hydrographic and tracer data. In contrast to previous theories of dense-water formation by deep convection in the Iceland and Greenland Seas, an alternative circulation scheme is presented in which the Atlantic Water in the northward flowing Norwegian Atlantic Current becomes gradually more dense by heat loss to the atmosphere and in which the dense water is transported to the outflow regions along the boundary currents surrounding the Iceland and Greenland Seas at shallow and intermediate depths. The overall circulation in the Nordic Seas that is consistent with these data is described. The cyclonic flow, fed by the Norwegian Atlantic Current, consists of three distinct branches: flow westward in the Fram Strait; flow northward through the Fram Strait and then through the Arctic Ocean; and flow passing through the Barents Sea and then through the Arctic Ocean. The branches, with modified hydrographic properties, return southwards as distinct layers of the East Greenland Current, the former two to supply the Denmark Strait overflow, the latter to supply the Iceland-Scotland overflow. The principal water mass product of the Iceland and Greenland Seas is an intermediate water mass that supplies the Iceland-Scotland overflow.