Agulhas ring Trajectories and Evolution from Altimeter data

Oceanic vortices have been the subject of several experimental and theoretical studies. They play a key role in the energy budget of the global ocean. A better understanding of their physics, (e.g. interaction with the mean currents) would improve our knowledge of the ocean circulation. Satellite altimeter data are used to detect, track and analyze the strong anticyclonic eddies generated by the Agulhas retroflection. These rings have a long lifetime and can cross the entire South Atlantic basin. They could play a key role in the exchanges between the Indian and South Atlantic oceans. Using a Gaussian eddy model and the smooth variation of eddy propagation speed, a method has been developed, based on an along track analysis of altimeter data in terms of eddy characteristics (amplitude, size) to estimate the eddy trajectory. This trajectory is then used as a frame of reference to estimate the bidimensional eddy structure. An Agulhas rings; detected during a WOCE campaign is studied. Its trajectory, its structure and its evolution are presented.