Dynamical Evolution of Intense Ierapetra Eddies on a 22 Year Long Period

Considered as wind forced, the recurrent formation of Ierapetra eddy affects the Eastern Mediterranean Sea circulation. Even though this large, coherent and long-lived anticyclone has been extensively studied, there are only few quantitative information on its dynamical characteristics. The main goal of this study is to quantify the Ierapetra Eddies (IEs) intensity and examine their seasonal and interannual variability over a 22 year period (1993-2014). We choose the automatic eddy detection algorithm AMEDA to estimate the main IEs dynamical parameters such as their size, their intensities and their lifetimes. Applied to daily AVISO altimetric products, the AMEDA algorithm allows a full characterization providing additional information on vortex velocity profiles as well as on merging and splitting events. Among the years of observations, the IEs Rossby number experience a strong variability and could vary by a factor 4 (Ro=0.07-0.27). This is mainly due to the eddy velocity variations rather than size variations. Moreover, we found that after their formation IEs could re-intensify. This intensification process may lead to a doubling of the vortex intensity in less than four months. That extra input of energy coincides with the Etesian winds period. Such high intensities are not expected from large-scale anticyclones and require cyclogeostrophic corrections. Considering this ageostrophic part, the maximum values of the core vorticity were derived and we found that the IEs might sometimes exhibit a negative potential vorticity core. Evidences on the eddy intensity from two oceanographic campaigns suggest that the IEs are probably more intense than we even estimate.