A bi-modal structure imposed on gravity driven boundary currents in rotating systems by effects of the bottom topography

An experimental observation related to the influence of the bottom topography on the development of gravity driven surface boundary currents in rotating systems is described and discussed. The results presented concern the local flow geometry in the vicinity of the head of the current. It is observed that, depending on the values of the independent experimental variables and the inclination angle of the bottom topography, the current propagates along the boundary with its head being either attached to or detached from the coastline. An appropriate scaling of the experimental data reveals that the attached and detached head mode occur in two distinct parameter regimes which are separated from each other by a well defined border. The discussion of the results suggests that this border identifies the division between two flow regimes in which the local flow structure in the vicinity of the head of the gravity current is and where it is not significantly influenced by the bottom topography.