Effects of bathymetry on long-range acoustic transmissions

Abstract

Long-range acoustic propagation has been used recently to perform basin scale inversions of the temperature field of the oceans. The inversion technique involves measuring acoustic travel times and inverting them for sound-speed structure using a forward acoustics model. Ocean acoustic tomography has generally been formulated and applied to problems with little bottom interaction where ray theory is a suitable forward model. Power and reduced source motion requirements have led the global acoustics community to use near-seafloor moored sources off the coast of islands or continents. We examine the effects that scattering with the seafloor near the source and near the receiver has on broadband acoustic signals. Comparisons are made between range-dependent oases, the parabolic equation, and ray codes for several bottom types and bathymetry contours. The effect of scattering on travel time structure in time/depth space as well as mode amplitudes will be addressed. The implications of this work to future plans for global scale acoustic thermometry and internal wave inversion will be presented.