A Numerical Model of Internal Wave Refraction in the Strait of Gibraltar

Abstract

The relative importance of depth, cross-strait interface till and horizontal current shear upon the wave front shapes of internal waves in the Strait of Gibraltar are examined by means of a numerical refraction model. Results from the model are also compared with observations of wave front shape made in the eastern strait using a shore-based marine radar, which imaged the surface effects of the waves. The model is linear and assumes a time-independent two-layer fluid in which the depth of each layer may be any function of position. The effect of current on the propagation is modeled by the addition of a term in the dispersion relation that increments the phase speed by an amount equal to the current component in the propagation direction, at the depth of maximum internal wave displacement. This current may also be any function of position. The results suggest that in the Strait of Gibraltar, interface tilt and horizontal shear both have a strong influence on the refraction, whereas total depth is not important except near the shore. When parameters consistent with available data from the strait are used, the predicted wave front shapes are very similar to those found in the radar images.