ACOUSTIC PROPAGATION THROUGH AN INTERNAL WAVE-FIELD IN A SHALLOW-WATER WAVE-GUIDE

This paper addresses the problem of predicting and interpreting acoust ic wave field properties in a stochastic ocean waveguide, for which th e sound-speed variability within the water column is treated explicitl y as a random process. It is assumed that the sound-speed distribution is composed of three components: a deterministic, time-independent pr ofile and two stochastic components induced by internal wave activity. One random contribution represents a spatially diffuse Garrett-Munk f ield whose spectrum is constrained by the shallow water waveguide, whi le the second corresponds to spatially localized soliton packets. A hi gh-angle elastic parabolic equation method is applied to compute singl e frequency realizations of the pressure field using this three-compon ent representation of the sound-speed distribution. Ensemble-averaged transmission loss and scintillation index measures for the full pressu re field and its modal components are estimated for different source d epths and for both flat and sloping bottoms. Probability distributions of the mode amplitudes for different ranges are also presented. These statistical measures are incorporated into the analysis of range-depe ndent mode coupling between the internal wave and acoustic fields, and evidence is presented which supports a recent prediction that the sci ntillation index grows exponentially with range due to the competition between mode coupling and mode stripping found in shallow water waveg uides. Full-field estimates of the scintillation index are also presen ted for a shallow water region on the continental slope off the New Je rsey coast. (C) 1997 Acoustical Society of America.