Influence of assimilated eddies on the large-scale circulation in a model of the northwest Atlantic Ocean

In this letter, we apply a novel technique (the “semidiagnostic method”) to assimilate the eddy field from a model with constrained large-scale circulation into a model version with an unconstrained large-scale circulation. Assimilation of the eddies (i) drives an anomalous circulation corresponding to the northern recirculation gyre of the Gulf Stream, but of insufficient strength to appear in the mean field and (ii) leads to a much enhanced circulation in the northwest corner, east of Newfoundland. We argue that the blocking of f/H contours from the east by the mid-Atlantic Ridge is a major influence on the dynamics of the northwest corner, and that the dynamics of the eddy-driven northern recirculation and the northwest corner are fundamentally similar.