Spatio-temporal evolution of two key processes impacting the observed vertical structure of the mesoscale eddies in the 4 major Eastern Boundary Upwelling Systems.

Mesoscale eddies are an important component of the Eastern Boundary Upwelling Systems (EBUS) since they can trap and redistribute sea-water properties from near-coastal to open ocean regions. Merging 10 years of satellite altimetry and concomitant Argo float data, we first depict the vertical structure of the main eddy-types (surface and/or subsurface intensified) generated in the coastal areas of the 4 major EBUS. In particular, the mean geographical distribution and the temporal evolution of their vertical structure, in terms of temperature (T) and salinity (S) anomalies, are studied. Then, using a relatively simple diagnostic, we investigate and quantify the respective role of the isopycnal advection and the vertical displacement of the water-column on the observed vertical structures for each eddy-types. These two processes largely explained the observed T/S anomalies within the eddies, except occasionally in the surface layer where ocean-atmosphere interactions and mixed-layer processes can also take place. Finally, the temporal evolution of these two contributions are investigated along composite eddy trajectories, from the near-coastal regions where they are formed to the open ocean where they dissipate. Thus, this study provides key informations on the mechanisms involved on the spatio-temporal evolution of the long-lived eddies in the 4 EBUS.