South eastern Mediterranean Sea (31-39 N ; 9-16 E)
Mediterranean Sea, Eastern Basin
EGITTO is an observational program to study the circulation in the south-eastern Mediterranean Sea and to confirm (or not) the various circulation patterns published in the literature based on in-situ observations, remote sensing data and models. The near-surface circulation eddy and seasonal variabilities are described with low-cost satellite-tracked drifters in c oncert with satellite observations of sea surface temperature, near -surface chlorophyll pigment concentration and sea surface dynamic topography. The main focus is on the Atlantic Water main pathways that have recently been represented as coastal and along-slope currents off the African coast and that are extremely unstable and generate energetic meanders and anticyclonic eddy circulationfeatures.In straight collaboration with French oceanographers and local Tunisian and Egyptian scientists, the surface circulation in the southeastern Mediterranean Sea is monitored for about a year with drifters released in the Strait of Sicily and off eastern Egypt on a seasonal basis. Eulerian (seasonal maps of mean currents and eddy variability) and Lagrangian (one and two-particle diffusion) statistics are computed. Satellite data are integrated with the drifter observations to study the circulation variations and their relations to the local wind forcing and the bottom topography. The main objective of EGITTO is to improve the understanding of marine environmental evolution, with particular emphasis on the eddy dynamics in marginal seas where the effect of bottom morphology, the forcing by sheared winds and fresh water inflow can be significant factors.It is obvious from the literature that the southeastern Mediterranean circulation is highly variable at eddy, seasonal and interannual scales, and that historical observations have provided only partial, inadequate, and even controversial descriptions due principally to the scarcity (and low quality) of in-situ observations. In conjunction with investigations proposed by French, Tunisian and Egyptian colleagues (including hydrographic surveys, moorings, surface drifters) a drifter experiment is conducted to elucidate the circulation patterns and to study the Atlantic Water pathways, including the Lybio-Egyptian Current and associated eddy instabilities. More specifically, the study of the southeastern Mediterranean near-surface circulation variability over an entire year using Lagrangian drifters and satellite products include the following activities: perform an extensive review of existing knowledge on the circulation of the southeastern Mediterranean Sea; describe the surface circulation variability (Eulerian and La grangian statistics, major scales of variability, particle dispersion, etc.) and separate this variability into mean (over a year) , seasonal (3 months), wind-related (split in wind regimes), synoptic (10 days) and mesoscale (a few days); describe the spatial structure and temporal variability of predominant eddy circulation features, such as the Mersa-Matruh and Shikmona Gyres in the southern Levantine sub-basin; relate the surface circulation characteristics derived from the drifter data to the thermal and pigment signatures observed from satellites; study the effect of wind forcing (e.g., the Etesians) and bathymetry on the surface circulation; combine concurrent drifter and satellite altimetry data and model simulations to construct accurate maps of mean absolute near-surface geostrophic currents.