A study of Mediterranean eddies by in situ and remote sensing methods

Ienna, Federico Salvatore
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University of Delaware
Subsurface coherent vortices in the North Atlantic, whose saline water originates from the Mediterranean Sea and which are known as Mediterranean Eddies ("meddies"), have been of particular interest to physical oceanographers since their discovery, especially for their salt and heat transport properties into the North Atlantic Ocean. Many studies in the past have been successful in observing and studying the typical properties of meddies by probing them with in-situ techniques. The use of remote sensing techniques would offer a much cheaper and easier alternative for studying these phenomena, but only a few past studies have been able to study meddies by remote sensing, and a reliable method for observing them remotely remains elusive. This research presents a new way of locating and tracking meddies in the North Atlantic Ocean using satellite altimeter data. The method presented in this research makes use of Ensemble Empirical Mode Decomposition (EEMD) as a mean to isolate the surface expressions of meddies on the ocean surface and separate them from any other surface constituents, allowing robust meddies to be consistently tracked by satellite. One such meddy is successfully tracked over a 6 month time period (2 November 2005 - 17 May 2006). Results of the satellite tracking method are verified using Expendable Bathythermographs (XBT). Furthermore, three other meddies are also studied by in-situ observations using Argo float data, and an analysis of the buoyancy frequency properties of meddies is made.