Mixing Inferred from Coherent Mesoscale Eddies (MICME)

This project will provide a new technique for estimating surface-layer mesoscale diffusivity by tracking coherent mesoscale eddies using satellite altimetry. The estimated diffusivities will help constrain the distribution of oceanic tracers and can be used to validate and improve mesoscale eddy parameterizations in numerical models. Development of this technique will also provide insights into dynamics of ocean macro-turbulence and the mechanisms of mesoscale eddy mixing, which could contribute to the understanding of eddy transport in a broad variety of flow regimes. The ocean components of modern climate models are of insufficient resolution to resolve mesoscale eddies; thus, eddy tracer transport is typically parameterized as a diffusive process. However, variations in the magnitude and spatial pattern of tracer diffusivity in these models can potentially lead to large differences in their simulated climates. This project will quantify the impact of coherent ocean eddies on mesoscale mixing. The central hypothesis is that the dispersion of coherent mesoscale eddies will provide an efficient estimate of the mesoscale diffusivity in the ocean. The first objective is to identify how inhomogeneity affects the relationship between the movements of coherent mesoscale eddies and tracer diffusivities in an idealized general circulation model. The project will then estimate the magnitude and anisotropy of global mesoscale eddy diffusivity with coherent mesoscale eddy trajectories from satellite altimetry. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.