Analysis of current metric measurements in the Gulf of Hammamet (Tunisia)

Abstract

The coastline of the Gulf of Hammamet is threatened by natural and anthropogenic degradation. This affects the quality of life and the strategic interests of the country. To understand the flow of water in this area, we deployed two current meters. Harmonic analysis of water levels indicates that the tidal harmonic M2 is dominant. The tide is semi-diurnal in the Gulf of Hammamet. The Analysis by the method of the empirical orthogonal function of the series of tidal currents speeds at the level of Gulf Hammamet shows that the surface current is oriented towards the northeast parallel to the coast with a maximum speed along the main axis of the order of 5.9 cm.s-1. The current near the bottom turns northwest and follows the -20 m isobath with a maximum speed of around 2.2 cm.s-1. The evolution of the speed vector and the direction of the current which is due to the phenomena of high frequency (tide) and low frequency (wind, swell and atmospheric pressure) during the recording period show that the direction is parallel to the coast in surface waters with a speed which can exceed 20 cm.s-1. However, the currents near the bottom are weaker but can exceed 10 cm.s-1. These currents follow the -20 isobath. Weak currents near the bottom may be associated with general circulation currents of Atlantic origin. It seems that surface currents are closely related to the combined effect of wind and swell and atmospheric pressure. The tide plays a rather weak role for the circulation of water in the Gulf of Hammamet. The analysis of the time series obtained in the Gulf of Hammamet allowed us to sketch the dynamic characteristics that prevail in the study region. It has been demonstrated the low tidal range (12 cm) and especially the presence of strong currents (15 cm.s-1) and whose direction alternates between North and South. The shape of the currents measured offshore is typical of a dynamic marked by a vortex structure.