Frictional sinking of the dense water overflow in a z- coordinate OGCM of the Mediterranean Sea

The overflow and subsequent spreading of dense water formed in the Adriatic Sea is studied in a high resolution z-coordinate ocean general circulation model (OGCM) of the Mediterranean Sea via simulations of chlorofluorocarbons (CFC12). Frictional sinking is investigated using different parametrisations of the mean bottom stress in term of the mean currents. A series of model integrations shows that increasing the strength of the bottom stress allows the dense overflow to descend the continental slope at a steeper angle, as would be expected on the basis of theoretical streamtube models. The use of a linear drag, which can be thought of as parametrising unresolved time-varying motions, greatly improves the model's ability to capture a realistic dense water pathway and hence realistic CFC12 distributions.