CoAuthors

Christine Provost (LOCEAN, France)

We analyzed physical parameters gathered by a mooring array at mesoscale spatial sampling deployed in Argentine Basin within the Ocean Observatory Initiative, a National Science Foundation Major Research Facility. The array was maintained at 42°S 42°W, a historically sparsely sampled region with small ocean variability, during 34 months from March 2015 to January 2018. The data documented four extreme oceanic events in 2016, a year that stands out with the highest level of eddy kinetic energy in the 29-year-long satellite altimetry record at the mooring site. The four events were anticyclonic structures, a meander of the Subtropical Front and three intense anticyclonic eddies with swirl velocities of the order of 0.4 m/s. Satellite altimetry provided complementary information on the size, origin and fate of the structures. The three anticyclonic eddies (named A1, A2' and A2") showed distinct characteristics. A1 was a large, 300 km-diameter, bottom-reaching eddy. In contrast, A2' and A2" were smaller with a size close to the Rossby radius (40 km) and a vertical extension of 2500 m. They were attenuated in the satellite altimetry maps. The high-frequency mooring data indicated the presence of near-inertial waves trapped at depth within the anticyclones and provided evidence of favorable conditions for the potential development of mixing well below the mixed layer.