PATHWAYS OF THE WATER MASSES EXITING THE LABRADOR SEA: THE IMPORTANCE OF BOUNDARY-INTERIOR EXCHANGES

The water masses exiting the Labrador Sea, and in particular the dense water mass formed by convection (i.e. Labrador Sea Water, LSW), are important components of the Atlantic Meridional Overturning Circulation (AMOC). Several studies have suggested that the eddy activity within the Labrador Sea is of high importance for the export route and the properties of the LSW. In this study, the pathways and the timescales of the water masses exiting the Labrador Sea are investigated by Lagrangian particle tracking. This method is applied to the output of an eddy- permitting idealized model that represents well the essential physical processes involved in the cycle of convection and restratification in the Labrador Sea. The Lagrangian trajectories reveal that the water masses that exit the marginal sea have followed either a fast route within the boundary current or a slow route that involves boundary current-interior exchanges. Regions characterized by enhanced eddy activity play a significant role in determining the properties and the timescales of the water masses exiting the marginal sea suggesting that the interior-boundary current exchange is governed by eddy activity. Analysis of the properties of the water masses along the different pathways shows that the densest water masses are the ones that pass through the interior, rather than the ones that follow the boundary current. This study highlights the importance of the exchanges between the boundary current and the interior of the marginal sea for the properties of the water masses that leave the Labrador Sea and the associated timescales.