Acoustic scattering by internal solitary waves in the Strait of Gibraltar

High-freqnency underwater acoustic transmissions across the Strait of Gibra ltar were used to examine acoustic scattering caused by the unique internal wave field in the Strait. Internal solitary waves of 100 m in amplitude pr opagate along the interface between an upper layer of Atlantic water and a lower layer of Mediterranean water. The interface is also strongly modulate d by internal tides of comparable amplitude. As internal solitary waves cro ss the acoustic path, they cause sharp soundspeed gradients which intermitt ently refract acoustic rays away from normal sound channels. Internal tides vertically shift soundspeed profiles for additional travel time variabilit y. Although the acoustic scattering is quite complicated, it is also surpri singly robust, making it a good candidate for modeling. Key features of the acoustic arrival pattern can be accounted for in some detail by a model de scription of the complex hydraulics in the Strait. (C) 2001 Acoustical Soci ety of America. [DOI: 10.1121/1.1329624].