Observation océanographiques dans le détroit de Gilbraltar pendant la campagne Phygib (Septembre - Octobre 1971)

Measurements in the strait of Gibraltar during the last fifteen years have shown the existence of large internal waves propagating at the interface between the upper layer of Atlantic water and the lower layer of Mediterranean water. These waves are generated by the tidal currents running over the sill. The scale of the phenomena are such that non linear variations of the flow in the strait as a fonction of the tidal amplitude can be expected. Specifically, mean Mediterranean outflow over a tidal period should be expected to increase going from neap to spring tides. To study these effects, two currentmeter and hydrological stations were made by the N. O. Le Noroit by the C.0.B.'s physics group in october 1971. The first series of observations made at the eastern entrance of the strait between the 9th and 12th of october during a period of neap tides indicate a strong diurnal variation in the flow. The second station, west of the sill, between the Maroccan coast and Spartel bank, was made to study the variations in the Mediterranean outflow, as a fonction of tidal amplitudes. These measurements show a twofold increase of this outflow (meaned over 24,8 h) between periods of neap tides (tidal coefficient CM : 38) and of spring tides (CM : 115). [NOT CONTROLLED OCR]