Chaotic mixing and fractals in a geophysical jet current

TL;DR

This paper models chaotic mixing in oceanic jet currents, revealing fractal structures and anomalous transport behaviors through a kinematic advection model with time-dependent meanders.

Contribution

It introduces a model demonstrating chaotic advection in geophysical jets with fractal mixing patterns and hierarchical scattering characteristics.

Findings

Chaotic advection occurs over a wide range of meander parameters.

Mixing geometry exhibits fractal-like structures.

Particle trapping times and rotations have hierarchical fractal distributions.

Abstract

We model Lagrangian lateral mixing and transport of passive scalars in meandering oceanic jet currents by two-dimensional advection equations with a kinematic stream function with a time-dependent amplitude of a meander imposed. The advection in such a model is known to be chaotic in a wide range of the meander's characteristics. We study chaotic transport in a stochastic layer and show that it is anomalous. The geometry of mixing is examined and shown to be fractal-like. The scattering characteristics (trapping time of advected particles and the number of their rotations around elliptical points) are found to have a hierarchical fractal structure as functions of initial particle's positions. A correspondence between the evolution of material lines in the flow and elements of the fractal is established.