A zoomed 3d circulation model for the Monastir bay (Tunisia) : comparison to operational analyses

Abstract

The present work aims at developing a zoomed 3D hydrodynamic model that simulates the circulation of water masses for the central-eastern coasts of Tunisia (Nabeul to Chebba) with the bay of Monastir in the center. The resolution of the model gradually increases from the edges (~ 1100 m) towards the bay of Monastir where it is of the order of 300 m. The model is forced at the sea surface by atmospheric data from a neighboring weather station and by ocean re-analyses. We present here a comparison between the results of the model and the reanalyses for the simulated year 2008. The outputs of the model show a strong seasonal cycle with winter cooling and summer warming more accentuated near the coasts. The surface salinity is modulated by the penetration of the Atlantic water vein in the Gulf of Hammamet, more important in summer. Near shallow coastal areas, the salinity is relatively high especially in the bay interior and is more accentuated in summer. The circulation is characterized by currents directed towards the southeast in winter and the west and northwest in summer. These simulation results are similar to those of the re-analyses. The re-analyses offshore currents are, however, oriented towards the southwest in summer. A comparison of vertical sections of temperature and salinity shows high agreement with the presence of the trace of the Atlantic water vein at a depth of about 50 to 60 m.