The three-dimensional Princeton Ocean Model is used to investigate the mean flow and the hydraulics regime in the Strait of Gibraltar. The model makes use of a coast- following curvilinear orthogonal grid that includes the Gulf of Cadiz and the Alboran Sea, with very high resolution in the strait ( 500 m). A lock-exchange initial condition is used: The western part of the model domain is filled with Atlantic water, whereas the eastern part is filled with Mediterranean water. A conservative, nondiffusive, and nondispersive numerical scheme for the horizontal tracers advection has been implemented to simulate the free-flow adjustment for the lock-exchange initial condition. Predicted velocities, interface depth, water, and salinity transports are comparable with observed data. Model results describe circulation of the Mediterranean outflow in detail and demonstrate the presence of a mixing layer between the Atlantic and Mediterranean water. The hydraulic regime is analyzed, calculating the composite Froude number for three layers within the strait. Results indicate the presence of a hydraulic control at Camarinal Sill and in the northern part of Tarifa Narrows. In order to understand if the Strait of Gibraltar is in the submaximal or maximal regime we have formulated a cross-strait mean composite Froude number. This formulation allowed us to limit the values of the composite Froude number in the range of 1.2-1.5 at Camarinal Sill and between 0.4 and 0.8 at Tarifa Narrows. We have concluded that the mean exchange simulated by the model is in submaximal regime.

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