Determination of environmental sensitivity of acoustic propagation on continental shelves using an equivalent fluid parabolic equation model

A coupled environment and acoustic prediction system was developed to evaluate the sensitivity of acoustic propagation on the continental shelf to water column and sediment properties. The acoustic prediction system used the range-dependent, parabolic-equation ifd model. Since the ifd-PE model is only applicable to a fluid bottom, an equivalent fluid bottom approximation was made to incorporate the elastic medium. The environment (coastal ocean) prediction system used a simulated time-varying temperature field for the northern California shelf, calculated from a ocean general circulation model. The solid bottom geoacoustic parameters were determined from Hamilton's model, using extensive sediment and seismic profile data. The acoustic propagation loss was calculated for the total 103-day period of upwelling season under various configurations of source depth, frequency, and topography. The environmental sensitivity was examined from the basic statistics. While this study is limited to the California shelf and for the upwelling season, the present approach suggests a method for systematic and realistic evaluation of acoustic variability on continental shelves.