Internal-wave effects on multi-megameter oceanic acoustic tomography

Parabolic-equation numerical simulations which utilize environmental data and which take into account sound-speed perturbations obeying the Garrett–Munk spectral model for internal waves have been carried out. Several effects of these simulated internal waves have been compared with path-integral calculations: of the internal-wave bias, the wander of the wave front assuming a fixed ray trajectory, and the fluctuation of arrival time due to other effects such as the spread of the arrived pulse. The range dependence of these effects were determined. The effects of internal tides on measurements of mesoscale structure will be discussed. Also discussed are the speed and coupling of the amplitudes of vertical acoustic modes as a function of frequency, range, and mode number. The implications of these findings for ocean acoustic tomography of mesoscale structure and of climate will also be discussed. [Work supported by ONR Ocean Acoustics.]