Atmospheric and oceanic forcing of the eddy kinetic energy in the Labrador Sea

The Labrador Sea is widely believed to be a key location for deep water formation, contributing to the Atlantic Meridional Overturning Circulation (AMOC). Water mass transformations in this region are strongly impacted by vortex dynamics. Large interannual variations in both eddy shedding and buoyancy transport from the boundary current have been observed but not explained, and are apparently sensitive to the state of the inflowing current. Heat and salinity fluxes associated with the eddies drive ventilation changes not accounted for by changes in local surface forcing, particularly during occasional years of extreme eddy activity, and constitute a predominant source of “internal” oceanic variability.

With ensembles of numerical experiments with a high-resolution regional model (ROMS), we quantify the sensitivity of eddy generation and property transport to variations in local and external forcing parameters. With these simulations, we successfully reproduce the observed interannual variability in the eddy kinetic energy in the convective region of the Labrador Basin and along the West Greenland Current (WGC). The results show that the central Labrador Sea basin is mainly externally forced, while the internal instability plays an important role in the WGC region. The atmospheric influence of North Atlantic Oscillation (NAO) is limited to the north part of basin. Also, the strength of the inflowing currents and the high-frequency component of the wind stresses have been found to significantly impact the behavior of modeled eddy kinetic energy.