Introduction

EGITTO is an observational program to study the circulation in the southeastern 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 concert 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 circulation features.

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.

Objectives

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 s patial 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.

Tasks

The EGITTO project is organized into the following tasks:

Task 1: Review of circulation

Task 2: Drifter procurement and deployments

Task 3: Data management

• Subtask 3.1: Near-real time during TOP
  
• Subtask 3.2: Database (after TOP)

Task 4: Data analyses

• Subtask 4.1: Surface velocity statistics
  
• Subtask 4.2: Comparison and combination of drifter, remote sensing observations and ancillary data
  
• Subtask 4.3: Construction of synthetic mean surface dynamic topography maps.

Collaborators

Consiglio Nazionale delle Ricerche (CNR), Italy

Drs. M. Astraldi and G. Gaspararini of CNR-ISMAR in La Spezia (astraldi@iof.cnr.it and gasparini@iof.cnr.it)

Dr. F. Fiorentino of CNR-IAMC in Mazara del Vallo (Sicily) (fabio.fiorentino@irma.pa.cnr.it)

Dr. M.-H. Rio of CNR-ISAC in Rome (MH.rio@isac.cnr.it)


Ente per le Nuove tecnologie, l'Energia e l'Ambiente (ENEA), La Spezia, Italy

Dr. G. Manzella (giuseppe.manzella@estinf.santateresa.enea.it)


Laboratoire d'Oceanographie et de Biogeochimie (LOB), La Seyne, France

Dr. C. Millot (cmillot@ifremer.fr)

Dr. I. Taupier-Letage (Isabelle.Taupier.Letage@ifremer.fr)


Collecte Localisation Satellites (CLS), Toulouse, France

Dr. P.-Y. Le Traon (Pierre-Yves.letraon@cls.cnes.fr)

Dr. G. Larnicol (Gilles.Larnicol@cls.fr)


Institut National des Sciences et Technologies de la Mer (INSTM), Salammbô, Tunisia

Dr. C. Sammari (Cherif.Sammari@instm.rnrt.tn)

Ms. Sana Ben Ismail (sana.benismail@instm.rnrt.tn)


National Institute of Oceanography and Fisheries (NIOF), Alexandria, Egypt

Dr. M. A. Said (mamsaid2@hotmail.com)


Alexandria University Department of Oceanography (AUDO), Alexandria, Egypt

Dr. A. El-Gindy (om: aelgindy@iaa.com.eg)


NAVOCEANO - Naval Oceanographic Office, Stennis Space Center, Bay St Louis, Mississippi

Dr. C. Horton (hortonc@navo.navy.mil)

Reports

Gerin R. & P.M. Poulain (2005)
Hydrographic structures and circulation outline of the southeastern Mediterranean off the Egyptian coast. OGS Tech. Report 42/2005 - OGA/23, OGS, Trieste, Italy. (pdf file)

Poulain, P.M., I. Taupier-Letage, R. Gerin and G. Notarstefano (2006)
Oceanographic Cruise EGITTO-1 R/V OGS - EXPLORA 11-18 November 2005 Trieste, Italy to Port Said, Egypt. Cruise Report. OGS Tech. Report 29/2006 - OGA/14, OGS, Trieste, Italy. (pdf file)

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