Material transport by oceanic mesoscale eddies is analysed in an
eddy-resolving model of the ocean circulation. The analyses are based
on ensembles of Lagrangian particle trajectories. It is found that
the turbulent transport is anisotropic, inhomogeneous, non-stationary,
intermittent, and strongly non-diffusive. Deviations from the
diffusive regime are due to the presence of coherent mesoscale
structures, such as transient currents, eddies, and planetary waves.
Parameterizing this kind of transport in coarse-grid ocean GCMs
requires new transport models, which are better than the commonly used
turbulent diffusion model. A hierarchy of simple, inhomogeneous and
non-stationary stochastic transport models is proposed for simulating
turbulent transport in the presence of coherent structures. The
hierarchy is rigorously formulated and then tested against the
eddy-resolving fluid-dynamic ocean circulation solutions.
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