Study of Multimodal Structure of the Baroclinic Tide in the Strait of Gibraltar

The multimodal structure of the baroclinic tides in the Strait of Gibraltar is studied using observations and numerical simulations. The existence of higher baroclinic modes in tidal signal was identified in measurements performed in the area of Camarinal Sill (CS). Observational data and model results revealed the presence of two types of tidal internal waves generated over CS. One propagates toward the Mediterranean and disintegrates into series of nonlinear short internal waves with amplitudes of 50 m and more. The second type, behind the first, propagates slower and has a longer wavelength. The vertical structure with both upward and downward displacements of isopycnals can be identified as a manifestation of higher baroclinic modes. Analysis of the empirical orthogonal functions of the ADCP measurements performed over CS and model time series has shown that the second baroclinic mode predominates in second type of internal wave.Its amplitude can reach one third that of the first baroclinic mode of the leading waves of depression. This work was supported by NERC grant NE/D007968/1.