High resolution, three dimensional modeling of the circulation in the Gulf of La Spezia (Northwestern Mediterranean)

A high-resolution (~ 50 m), three-dimensional numerical model is used to assess dynamics and circulation patterns in the Gulf of La Spezia. The focus is on the water exchanges between the inner and outer parts of the Gulf, connected by two openings of a breakwater. Different simulations are run by varying idealized forcings, namely a) the semidiurnal tide, b) winds and c) the stratification. Differences in the runs are quantified in terms of mass transports at the two openings. The main result is that in presence of stratification and under “Scirocco” winds, a cyclonic circulation develops in the inner part of the Gulf, forcing waters to enter at the east opening and leave at the west opening. The effects due to semidiurnal tides and breezes are instead less important and result in almost null net water exchanges at the two openings. Maximum water exchanges between the inner and outer parts of the Gulf are registered under “Scirocco” winds and in stratified conditions, with average transport values of 87 m³/s leaving the inner Gulf at the west opening versus 92 m³/s entering at east. Results also show that the west opening is about two-fold more energetic than the east one (standard deviations of about 170 vs. 85 m³/s) and that variability in both openings is independent of the different forcings.