Dissipative inertial transport patterns near coherent Lagrangian eddies in the ocean

TL;DR

This paper demonstrates that inertial effects of buoyant particles in ocean flows explain dissipative patterns near coherent Lagrangian eddies, reconciling observations with theoretical flow structures.

Contribution

It introduces a model incorporating inertial effects into Lagrangian eddy analysis, explaining observed dissipative patterns in oceanic drifting objects.

Findings

Anticyclonic eddies attract negatively buoyant particles.

Cyclonic eddies attract positively buoyant particles.

Results explain satellite-tracked drifter and extit{Sargassum} distributions.

Abstract

Recent developments in dynamical systems theory have revealed long-lived and coherent Lagrangian (i.e., material) eddies in incompressible, satellite-derived surface ocean velocity fields. Paradoxically, observed drifting buoys and floating matter tend to create dissipative-looking patterns near oceanic eddies, which appear to be inconsistent with the conservative fluid particle patterns created by coherent Lagrangian eddies. Here we show that inclusion of inertial effects (i.e., those produced by the buoyancy and size finiteness of an object) in a rotating two-dimensional incompressible flow context resolves this paradox. Specifically, we obtain that anticyclonic coherent Lagrangian eddies attract (repel) negatively (positively) buoyant finite-size particles, while cyclonic coherent Lagrangian eddies attract (repel) positively (negatively) buoyant finite-size particles. We show how these results explain dissipative-looking satellite-tracked surface drifter and subsurface float trajectories, as well as satellite-derived \emph{Sargassum} distributions.