Spectral Decomposition of Frontal Submesoscale Dynamics and Eddy Splitting

Résumé fourni par la source

Submesoscale dynamics play a crucial role in vertical transport and energy redistribution in the upper ocean but remain challenging to observe due to their small spatial and temporal scales. Spectral Helmholtz decomposition of velocity from a shipboard acoustic Doppler current profiler allows examination of the scale- and depth-dependent partitioning of kinetic energy into rotational and divergent components. This method is applied to repeated high-resolution transects across a submesoscale front, which later splits into a cyclonic eddy in the Mediterranean Sea. We find a transition from balanced, rotational dynamics at scales greater than 10 km to divergent, unbalanced motions at submesoscales below 10 km. Divergent energy is enhanced in the mixed layer during periods of strong frontal strain, eddy deformation, and Rossby numbers of O(1), and appears linked to near-inertial wave interactions.

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