The Labrador Coastal Current: Observations from Surface Drifters and Autonomous Gliders

This study focuses on the Labrador Coastal Current (LCC), which is the coastal branch of the Labrador Current System (LCS). We characterize the LCS by combining existing Global Drifter Program (GDP) data with new surface drifters deployed by the Community-based Observations of Nunatsiavut Ocean Circulation (CONOC) project, specifically designed to fill the near-coast gap where the LCC lies. Autonomous ocean gliders are used to map hydrography and infer baroclinic and barotropic circulation components of the LCS. Tidal currents are generally weak across most of the shelf but are notably stronger in areas such as the Hudson Strait and the Strait of Belle Isle. The main Labrador Current (MLC), over the shelf break, exhibits strong currents (ca. 0.5 m/s) while the LCC, closer to the Labrador coast, shows moderate speeds of up to 0.25 m/s. Combining drifter- and glider-derived velocities, we find that the surface velocities in the LCC are predominantly barotropic (ca. 70%) while in the MLC they are predominantly baroclinic (ca. 70%). While volume transports in the MLC are several times larger than the LCC, their freshwater transports are comparable in magnitude. These observations provide crucial detail on the dynamics and watermass properties of the LCC.