The Maxwell Effect and the Material Transport by Transient Eddies

Mesoscale eddies-irregular time-dependent currents with lateral scales of 10-200 km-are ubiquitous in the World Ocean. They profoundly affect general circulation and actively redistribute oceanic heat, salt, biogeochemical tracers, and pollutants. The development of accurate parameterizations of eddy-induced transport remains one of the most pressing challenges in physical oceanography. Commonly used mesoscale parameterizations assume that the relation between eddy-induced fluxes and the large-scale property gradients is local and instantaneous. The present communication challenges this premise. We consider a closure that incorporates a delay in the adjustment of eddy fluxes to changing ambient distribution of properties. This model is inspired by the century-and-a-half-old idea of Maxwell, who argued that molecular dispersion necessarily involves a finite relaxation period. In our study, this principle is reinterpreted in the context of the turbulent transport problem. A series of simulations reveal marked improvements in eddy parameterizations brought by the inclusion of Maxwell's effect.