The residence time and overturning circulation of the Gulf of Gabès in the Eastern Mediterranean Sea

The water mass transformation in the Gulf of Gabès and its associated overturning circulation is investigated. The strong all year evaporation in the Gulf leads to a salinification of the entering water masses, which hence return with a strong salinity increase.  The heat transports in and out have a strong seasonal cycle, with approximately as much entering as exiting the Gulf in the yearly mean.

The overturning circulation is calculated from Lagrangian trajectories, which makes it possible to follow in detail the water mass transformation from where the water enters in the north, following an anticlockwise circuit along the coast in the Gulf until it exits in the southeast. The densest and most saline water exits, however, in the deepest middle part of the Gulf, where it tends to mix with the slightly fresher Mediterranean Waters. The trajectories are computed with the velocity and mass transport fields from a high-resolution (1/96°) hydrodynamic model, which includes the strong tides in this part of the Mediterranean.

 

Figure: Examples of trajectories entering and exiting the Gulf of Gabès. Colour for individual trajectories as a function of salinity.