Coherent Vortex Detection from Particles Trajectories Analysis

International audienceWe study the transport properties of mesoscale eddies (i.e. vortices between about 10 and 500 km in diameter) over a finite time duration. While these oceanic structures are well known to stir and mix surrounding water masses by their swirling motion, they can also carry and transport organic matter and marine in a coherent manner. Here we are particularly interested in those that remain coherent, despite the chaotic nature of the system. Existing techniques to analyze such Coherent Vortices rely on the classical geometric theory of invariants of the Cauchy–Green strain tensor, where closed orbits of line fields associated with this later are defined as vortices. Others define coherent vortices from vorticity, by calculating its averaged deviation. In this work, we take a very different approach, based upon a rigorous analysis of particles trajectories. Our method identifies coherent vortices and their centers acting as observed attractors for light particles in an automatic manner. We illustrate our new method on ocean surface velocities derived from satellite altimetry