The Labrador Current transports cold, relatively fresh, and well-oxygenated waters within the subpolar North Atlantic and towards the eastern American continental shelf. The relative contribution of these waters to either region depends on the eastward retroflection of the Labrador Current at the Grand Banks of Newfoundland. This paper develops a retroflection index based on the pathway of virtual Lagrangian particles and shows that strong retroflection generally occurs when a large-scale circulation adjustment, related to the subpolar gyre, accelerates the Labrador Current and shifts the Gulf Stream northward, partly driven by a northward shift of the wind patterns in the western North Atlantic. A mechanistic understanding of the drivers of the Labrador Current retroflection should help predict changes in water properties in both export regions and anticipate their impacts on marine life and deep-water formation.

Mathilde Jutras, Carolina O. Dufour, Alfonso Mucci, Lauryn C. Talbot