Observations of a Filamentous Intrusion and Vigorous Submesoscale Turbulence within a Cyclonic Mesoscale Eddy

Oceanic submesoscale flows are considered to be a crucial conduit for the downscale transfer of oceanic mesoscale kinetic energy and upper-ocean material exchange, both laterally and vertically, but defining observations re-vealing submesoscale dynamics and/or transport properties remain sparse. Here, we report on an elaborate observation of a warm and fresh filament intruding into a cyclonic mesoscale eddy. By integrating cruise measurements, satellite observa-tions, particle-tracking simulations, and the trajectory of a surface drifter, we show that the filament originated from an an-ticyclonic eddy oediately to the west of the cyclonic eddy, and the evolution of the filament was mainly due to the geostrophic flows associated with the eddy pair. Our observations reveal the mass exchange of the eddy pair and suggest that submesoscale flows can degrade the coherence of mesoscale eddies, providing important implications for the transport properties of mesoscale eddies. Vigorous submesoscale turbulence was found within the eddy core region, due to filamen-tous intrusion and frontogenesis. Our findings have thus offered novel insights into the dynamics and transport properties of oceanic submesoscale flows, which should be taken into account in their simulation and parameterization in ocean and climate models.

Automated summary

In this study, an elaborate observation of a warm and fresh filament intruding into a cyclonic mesoscale eddy is reported. The filament originated from an anticyclonic eddy and its evolution was mainly due to the geostrophic flows associated with the eddy pair. The findings provide important insights into the dynamics and transport properties of oceanic submesoscale flows.