Circulation and transport in the western boundary currents at Cape Farewell, Greenland

Abstract

The circulation and volume transports in the western boundary currents around Cape Farewell, Greenland, are derived from full-depth hydrographic and velocity measurements from August-September, 2005. The western boundary currents from surface to seafloor transport 40.5 ± 8.1 Sv southwards in the Irminger Sea, and 53.8 ± 10.8 Sv northwards in the Labrador Sea. The Deep Western Boundary Current (DWBC, defined as water with potential density greater than 27.80 kg m-3) transports 12.3 ± 2.5 Sv southwards in the Irminger Sea. The deep water transport is reduced south of Cape Farewell, where it changes flow direction from southwards to northwards (the south corner). At a section over the Eirik Ridge, a bathymetric feature extending southwest of Cape Farewell, the DWBC transports 8.7 ± 1.7 Sv westwards. The reduction in transport at the south corner is associated with decreased velocities within the deepest layers, and the volumetric loss of the most saline deep water types. The observations suggest that the part of the shallow and deep western boundary currents diverge at the south corner. Downstream in the eastern Labrador Sea the deep water transport is increased to 19.7 ± 3.9 Sv northwards, with the addition of recirculating denser deep waters. The representativeness of the results from the semi-synoptic survey are discussed with reference to companion current meter measurements of the DWBC.

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