Observations de fronts internes dans le détroit de Gibraltar pendant la campagne océanographique OTAN 1970 et interprétation des résultats par un modèle mathématique

MM. Lacombe, Frassetto and Ziegenbeim's observations, based on different measurement methods, demonstrated the existence of inner fronts and short period oscillations at the interface separating the Atlantic and Mediterranean waters in the eastern part of the Gibraltar straight. These observations show that inner fronts are created by the following mechanism: during the incoming tide, the westward current pushes the Mediterranean waters against the threshold of Gibraltar and, when getting to high tide, when the tide current becomes null, the interface is far from a balanced position, too high to the east, too low to the west of the threshold. The density currents caused by this imbalance creates an inner front of amplitude of more than 50 m which moves towards the east at a speed of around 3 to 4 knots at the sea bottom. This front is followed by oscillations with periods of around 10 to 20 minutes whose origin is the same as that of the oscillations of the undulatory jump for surface flows.