Wind-Driven Recirculations and Exchange in the Labrador and Irminger Seas*

Abstract

Abstract It is demonstrated that recently observed cyclonic recirculation gyres in the Irminger and Labrador Seas may be forced by the strong cyclonic wind stress curl that develops each winter seaward of the east coast of Greenland. Idealized analytical and numerical models forced with such variable winds over a sloping bottom reproduce the essential aspects of the observed gyres (strength, location, and horizontal and vertical length scales). The communication between the forcing region in the Irminger Sea and the recirculation to the west is achieved by baroclinic topographic Rossby wave propagation along potential vorticity contours. The circulation is characterized as a time-dependent, stratified, topographic beta plume. For weak stratification, as found in the subpolar North Atlantic, the recirculation strength exhibits only weak seasonal variability, consistent with the observations, even though the forcing is active only during the winter. Baroclinic Rossby waves that develop when the wind forcing ceases in springtime interact with the bottom to provide a source of cyclonic vorticity that maintains the circulation until the wind strengthens again in the following winter.