Ocean sound channel ray path perturbations from internal-wave shear and strain

Abstract

The relative importance of internal-wave strain and internal-wave shear on perturbation of acoustic ray trajectories in the ocean is analyzed. Previous estimates based on the Garrett-Munk internal-wave spectral model are updated using data from recent field studies of internal waves. Estimates of the ratio of the rms shear effect to the rms strain effect based on data from the upper kilometer of ocean are as high as 0.25–0.4, exceeding the estimates of 0.08–0.17 stemming from the model. Increased strength of three phenomena that have shear to strain ratios higher than the internal-wave average can cause this effect. These are near-inertial waves, internal tides, and vortical modes.