Lagrangian characterization of circulation over submarine banks with application to the outer Gulf of Maine

Abstract

A method to obtain an overall description of the Lagrangian circulation in complex two-dimensional time-periodic current fields is illustrated. The method involves the identification of hyperbolic fixed points in the Lagrangian residual displacement field, and the manifolds on which particles move to or from these points. In idealized current fields for the outer Gulf of Maine, a regular regime with bank-scale eddies is found for fields composed of periodic M2 tidal currents and various linear combinations of steady currents driven by tidal rectification, wind stress, and Scotian Shelf inflow. The size, strength, and presence of the eddies depend on the current field. A chaotic regime is found in the tidal and tidal-residual currents on central Georges Bank when resolution of the small-scale topography is improved, and in the Browns Bank region when periodic currents driven by storm-intensity wind stress are added. -from Authors