Modeling material transport by oceanic circulation

Material spreading and mixing by oceanic mesoscale eddies are analyzed in an idealized, numerical model of the wind-driven, mid-latitude ocean circulation. The analyses are based on ensembles of Lagrangian particle trajectories. The single-particle dispersion, which describes the spreading, is generally anisotropic and inhomogeneous, and in most places it is not diffusive (i.e., not linear in time) during intermediate-time intervals after release. A hierarchy of inhomogeneous and non-stationary stochastic models of material transport is rigorously formulated, its properties are described, and each model is fitted to an eddy-resolving solution of idealized, mid-latitude ocean gyres. The models provide more skillful parameterizations of the sub-grid-scale material transport induced by unresolved mesoscale eddies than the commonly used eddy-diffusion model.