Lagrangian Characterization of Circulation over Submarine Banks with Application to the Outer Gulf of Maine

Abstract

Abstract A method to obtain an overall description of the Lagrangian circulation in complex two-dimensional time-periodic current fields is illustrated through its application to current fields from a numerical model of the Gulf of Maine. The method. originally developed to analyze nonlinear dynamical systems, involves the identification of hyperbolic fixed points in the Lagrangian residual displacement field, and the manifolds on which particles move to or form these points. In a “regular” regime, these manifolds are separation lines that form the outer boundary of eddies within which particles remain trapped. In a “chaotic” regime, the manifolds have wild oscillations indicating a strong sensitivity of particle trajectories to their initial position and a chaotic stirring of particles across the former separation lines. 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 combination...