ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2aAO10. Internal wave effects on shallow water acoustic tomography.

Xin Tang

F. D. Tappert

Appl. Marine Phys., Univ. Miami, RSMAS, 4600 Rickenbacker Cswy., Miami, FL 33149

Full-wave numerical simulations of internal wave scattering of sound in shallow water are performed with an efficient broadband PE model that also includes scattering by bathymetric variations. Bathymetric scattering by itself gives an exponentially large number of unresolvable multipaths as predicted by ray chaos theory. When internal waves that evolve dynamically in geophysical time are included, the unresolvable multipaths are found to be temporally unstable with coherence times less than a few minutes at ranges greater than a few tens of water depths in shallow water, except possibly for rare paths that are shielded from internal waves such as within strong surface ducts. Since traditional travel-time ocean acoustic tomography requires many stable, resolvable and identifiable paths, conditions that are not satisfied in shallow water at longer ranges, some other inversion method will have to be developed for remote sensing of shallow water environments. [Work supported by ONR.]