Spreading of Labrador sea water: an advective-diffusive study based on Lagrangian data

Abstract

The pathways and timescales for the spreading of Labrador Sea Water (LSW) in the subpolar North Atlantic are investigated with an advective–diffusive model. The model's mean flow and eddy diffusivity are derived from float measurements, while the region of LSW formation is obtained from hydrographic data. Two main export pathways for LSW are reproduced by the model: eastward into the Irminger Sea and southward via the Deep Western Boundary Current (DWBC). The mean interior flow field in the Labrador Sea is found to play an important role in feeding both pathways. In particular, flow into the Irminger basin is due to a cyclonic recirculation located southwest of Greenland while the export via the DWBC is partially maintained through an internal pathway, transporting LSW across the basin to the west Greenland coast. A region of high eddy kinetic energy west of Greenland tends to increase the flushing rate of LSW, but its impact is found to be limited. The residence time for LSW in the Labrador basin is estimated to be approximately 4–5 years, with 80% leaving via the DWBC and 20% via the Irminger pathway.