Importance of anisotropic flow components for oceanic eddy-induced transport

This study explores the properties and origins of the oceanic eddy-induced material transport, using numerically simulated Lagrangian particle trajectories. This transport is strongly anisotropic, with the spreading rate in one direction ("major" direction) significantly exceeding the spreading rate in the across direction ("minor" direction), and is controlled by transient eddies with long length scales. In this regard, two types of spectral modes are critical for setting the anisotropic properties of the material transport: one corresponding to zonally-elongated Fourier modes (ZEMs), and the other - to meridionally-elongated Fourier modes (MEMs). In particular, ZEM-part of the spectrum dominates the zonal velocity variance and zonal material transport, and the MEM-part - the meridional velocity variance and meridional material transport. The velocity variance in the zonal and meridional directions are similar, but the Lagrangian decorrelation time scales are significantly longer in the major direction than in the minor one, and the anisotropy of the material transport cannot be derived from the velocity variance alone.; Anisotropic spectrum of transient eddies. Spectral power is shown as a function of zonal (x-axis) and meridional (y-axis) wavenumbers, nonimensionalized by the Rossby deformation radius. Note peaks corresponding to zonally- and meridionally elongated modes (ZEMs and MEMs).