Meeting Abstracts
Lagrangian Observations of Formation and Propagation of Subpolar Eddies into the Subtropical North Atlantic
Amy Bower, Ross Hendry, Daniel Amrhein, Jonathan Lilly
Woods Hole Oceanographic Institution
(Abstract received 05/17/2012 for session A)
ABSTRACT
Subsurface float and moored observations are presented to show for the first time the formation and propagation of anticyclonic submesoscale coherent vortices that transport relatively cold, fresh subpolar water to the interior subtropical North Atlantic. Acoustically tracked RAFOS floats released in the southward-flowing Western Boundary Current at the exit of the Labrador Sea reveal the formation of three of these eddies at the southern tip of the Grand Banks (42°N, 50°W). It was found that the eddies had average rotation periods of 5–7 days at radii of 10–25 km, with mean rotation speeds of up to 0.3 m s-1. One especially long-lived (5.1 months) eddy crossed under the Gulf Stream path and translated southwestward in the subtropical recirculation to at least 35°N. Velocity, temperature and salinity measurements from a nine-month deployment of two moorings south of the Gulf Stream at 38°N, 50°W reveal the passage of at least two eddies with similar hydrographic and kinematic properties. The core temperature and salinity of the eddies imply their formation at intermediate levels of the Labrador Current south of the Tail of the Grand Banks. These observations confirm earlier speculation that eddies form in this region and transport anomalously cold, low-salinity water directly into the subtropical interior. Time permitting, the float trajectories showing eddy formation will be compared to Lagrangian output from a high-resolution North Atlantic simulation.