Dynamical Processes within an Anticyclonic Eddy Revealed from Argo Floats

Mesoscale eddies play a significant role in supplying the nutrients required for phytoplankton blooms and redistributing biomass in the ocean. However, how anticyclonic eddies influence nutrient flux and biomass distribution remains unclear and controversial. Here we reveal two important dynamical processes (radial displacement and vertical fluctuations) within an anticyclonic eddy using observations from Argo floats. Particles in the eddy were displaced toward the eddy edge due to the imbalance of radial momentum. Vertical fluctuations below the mixed layer resulted in alternating upwelling and downwelling in the inner and outer parts of the eddy. High salinity deep water was uplifted tens of meters by the upwelling and further extended to the surface with the aid of wind effects and submesoscale effects. Vertical motions associated with the fluctuations penetrated into the layer of several hundred meters deep. These processes exhibit crucial dynamical mechanisms for the motion of particles in mature anticyclonic eddies.