Remote control of the retroflection of the Labrador Current

Abstract The Labrador Current carries cold, relatively fresh, and well-oxygenated waters into the subpolar North Atlantic and into the Slope Sea. The relative contribution of these waters to either region depends on the eastward retroflection of the Labrador Current at the Grand Banks. We develop a retroflection index based on virtual Lagrangian particles and show that the amplitude of the retroflection is mostly controlled remotely by large-scale forcing, related to winds over the Labrador Shelf and to subpolar gyre dynamics, whereas eddies and meanders arising from interactions between the Labrador Current and the Gulf Stream play a secondary role. The mechanistic understanding of the drivers of the Labrador Current retroflection should help to predict changes in the water properties of both export regions, and anticipating their important consequences on marine life and deep-water formation.