Scale-Dependent Eddy Diffusivities at the Kuroshio Extension: A Particle-Based Estimate and Comparison to Theory

Abstract For eddy-permitting climate models, only eddies smaller than the smallest resolvable scale need to be parameterized. Therefore, it is important study diffusivities induced by a specific separation L * , that is, scale-dependent eddy diffusivities. Using submesoscale-permitting model solution (MITgcm llc4320), we estimate diffusivity in Kuroshio Extension. We find that, as increases, and spatial structure approaches of total diffusivity. quantify this dependence through fitting n . Our derivation shows approximately ( + 1)/2, where kinetic energy spectral slope. domain-averaged diffusivity, 1.33. then extend four existing mixing theories including dependence. results show both designed for intense-jet regions, suppressed length theory multiwavenumber theory, closely match magnitude but fail capture well diffusivity’s structure. However, other two based on size Rhines can reasonably represent Based finding, propose an empirical formula represents work demonstrates models should use designing appropriate formulas may reasonable approach these Also, our diagnostic framework applicable global ocean.