A physical model of the Gibraltar Strait: the HERCULES experiment

Gravity currents are one of the key sub-mesoscale processes that drive energy transfer, impact the thermohaline structure and the vertical exchange of water masses in the ocean. At present, their representation remains difficult in numerical models. The targeted study area is the Strait of Gibraltar between the Mediterranean and the Atlantic Ocean. We present preliminary results of experiments obtained using the first realistic implementation of the Strait of Gibraltar with the adjacent Gulf of Cadiz and Alboran Sea, including all main forcings: the density difference, the barotropic tide, the Earths rotation and the realistic topography, scaled using available in-situ data. Detailed measurements of the velocity and density fields reveal that the large-scale circulation and the further faith of the Mediterranean waters flowing into the Atlantic Ocean are strongly influenced by the turbulent processes at small scale that take place in the main control areas, i.e. the Camarinal and Espartell sills. Two-dimensional velocity and density fields in these key regions and in several locations in the Gulf of Cadiz and Alboran Sea are obtained and turbulent fluxes and mixing are estimated. Finally, internal solitary waves are observed, possibly degenerating in a train of internal waves, generated by the tide in interaction with the topography at Camarinal sill and propagating toward the Alboran Sea. These results are analyzed to assess the impact of the parameter variation (barotropic and baroclinic forcings).