Spiral eddies in the Aegean Sea derived by satellite radar data

Ocean mesoscale spiral eddies is a phenomenon that came apparent in the last 50 years but until today there are many questions yet to be answered about their formation, distribution and correlation to the dynamical processes on the sea surface. Main objective of the present paper is to provide an extensive analysis on the occurrence and statistics of small-mesoscale eddies over the Aegean Sea using synthetic aperture radar (SAR) images. The study area is characterized from unique hydro-dynamical and topographical conditions that give another aspect on the phenomenon. Present study based on 169 medium resolution (WSM) ENVISAT ASAR images acquired in 2011. As a result of the analysis 192 eddies formations were detected. The majority of those eddies were visualized due to the presence of surfactant films (black eddies) on sea surface and majority of them were cyclonically rotating. The diameter of the observed formations of eddies was within 1 to 16 km. The detected eddies were classified by categories depending on their shape and their generation mechanism. Seasonal and spatial distribution is presented, in order to understand their variability compared with the upper surface circulation. The value of the baroclinic Rossby radius of deformation was used for the discrimination of wind driven or geostrophic balanced spiral eddies. Though most of the observed formations seem to be wind driven, an important correlation with the upper circulation of the Aegean Sea is shown.