Short-period cross-strait internal waves from wave-topography-hydrodynamics interactions: Observations and 3-D model results in the strait of Gibraltar

Abstract

The origin, characteristics, and behavior of cross-strait short-period internal waves in the Strait of Gibraltar are analyzed, by means of a 3D, baroclinic, non-hydrostatic, hydrodynamic model, as well as satellite SAR images. The origin of these cross-strait waves was found to be related to the reflection of the main longitudinal (along-strait) internal wave on the continental shelf slope, where the reflected wave is firstly arrested by the eastward tidal current, and then released towards the northern coast once this tidal current has weakened enough to achieve its subcritical value. The main example of this topographic wave interaction is the cross-strait internal wave reflected from the African shore east of Tangier Bay, which propagates north-westwards towards the Iberian coast near Tarifa. Other waves along the Strait are also found. The latter explains the presence of internal waves in unexpected directions of propagation at times far later than the main longitudinal wave at certain locations, all of them with plausible influence on mixing processes, upwelling phenomena and biogeochemical activity in the area.