Spatiotemporal Variations and Parameterization Scaling of Submesoscale Eddy Diffusivity in the Global Ocean

Abstract Submesoscale eddies are important horizontal transporters of oceanic heat, salt, and other tracers, and their transporting efficiency is described using an eddy diffusivity in analogy with molecular diffusion. Although submesoscale eddies have been widely studied, global submesoscale eddy diffusivity ( K sm ) remains poorly known, whose knowledge is crucial to improve models' climate simulation and projection. Here, global spatiotemporal variations of K sm are for the first time quantified using a state‐of‐the‐art high‐resolution global simulation. We find that K sm is elevated in mesoscale eddies rich regions, peaking in subtropical countercurrents around 20°N/°S. K sm is stronger in winter than in summer, with global median values of 103 m 2 s −1 in winter and 62 m 2 s −1 in summer. We further propose that the product of root‐mean‐squared submesoscale kinetic energy and submesoscale energy‐containing scale is a good parameterization scaling of K sm . These findings lay the foundation for improving the parameterization scheme of climate models.