Geometry of Cross-Stream Mixing in a Double-Gyre Ocean Model

Abstract

New dynamical systems techniques are used to analyze fluid particle paths in an eddy resolving, barotropic ocean model of the Gulf Stream. Specifically, the existence of finite-time invariant manifolds associated with transient, mesoscale events such as ring detachment and merger is proved based on computer-assisted analytic results. These ?Lagrangian? invariant manifolds completely organize the dynamics and mark the pathways by which fluid parcels may be exchanged across stream. In this way, the Lagrangian flow geometry of a detaching ring or a ring?jet interaction event, as well as the exact associated particle flux, is obtained. The detaching ring geometry indicates that a significant amount of the fluid entrained by the ring originates in a long thin region on the far side of the jet and that this region extends as far upstream as the western boundary current. In the ring?stream interaction case, particle transport occurs both to and from the ring and is concentrated in thin regions on the near side of the jet and around the perimeter of the ring.