Estimation of bottom parameters using measurement and analysis of sound intensity fluctuations in the presence of moving nonlinear internal waves in shallow water

Methodology of estimation of bottom parameters is proposed using data processing and analysis of sound intensity fluctuations due to mode coupling in the presence of moving nonlinear internal waves (NIW) in shallow water channel. As an examples experiments Shallow Water 2006 (Atlantic shelf of USA) [1] and ASIAEX 2001 (South China sea) [2] are considered. In these experiments NIW generated in area of the shelf break were moving approximately along acoustic track with the length about a few tens of km. Spectra of intensity fluctuations of the sound intensity of pulses during a few hours on vertical line array (VLA) due to mode coupling in both experiments have specific peaks corresponding to the difference between wave numbers of coupling pairs of modes. Analysis of fluctuation spectra includes both temporal dependence of fluctuations on separate hydrophones and temporal dependence of intensity summarized over VLA. It is shown that geoacoustic inversion in given case can be achieved using comparison of experimental spectral and temporal dependencies and results of theoretical modeling, containing bottom characteristics (sound speed density and attenuation) as a fitting parameters.