Chaotic transport in a double gyre ocean

Abstract

Lagrangian trajectories in a deterministic simple flow can exhibit complex behavior. This is called the chaotic advection, which can induce the chaotic transport and mixing (which oceanographers conventionally call stirring) in the fluid particles and fine structure in the tracer fields. We propose the chaotic transport as a gyre‐scale transport mechansim in oceans. Our model ocean has double gyres, subtropical and subpolar gyres, driven by the surface wind. When the wind is allowed to seasonally migrate, the inter‐gyre transport and across streamline transport within each gyre will be excited. The fastest inter‐gyre transport occurs when the wind migrates about 1000km in north‐south direction with a period of interannual to decadal time. The estimate of the effective diffusion coefficient by this gyre‐scale mixing is about 3 × 107cm2s−1, comparable to those derived for synoptical eddies. The results shed some light on gyre‐scale exchange of water and heat flux in general oceans and implications for the studies of ocean climate. The concepts and methods used here will find applications in coastal oceanography, ocean biology and chemistry.