Reconstructing meso- and submesoscale dynamics in ocean eddies from current observations

We reconstruct the 3-D meso- and submesoscale structure of selected oceanic eddies from ship-based field observations of current velocity, in the mixed layer and below, in order to explore two main questions: what information on upwelling/downwelling can be derived; and inside what eddy radius is water trapped and transported.

The selected eddies have been intensively surveyed during the collaborative project REEBUS (Role of Eddies in the Carbon Pump of Eastern Boundary Upwelling Systems) in the eastern tropical North Atlantic. Making use of vertical sections of current velocities we fit an optimum eddy-like structure to the data. The structure is assumed a slowly drifting, circular symmetric but not necessarily linear velocity field, separated in horizontal layers. The composition of the reconstructed layers provides a 3-D velocity structure which is used to calculate derived variables as vorticity and divergence. We find submesoscale divergence patterns which support vertical flux occurring in the eddies. We further use current velocities from a high-resolution regional model based on ROMS to validate the method and estimate uncertainties.