Sensitivity of ray dynamics in an underwater sound channel to vertical   scale of longitudinal sound-speed variations
  We investigate sound ray propagation in a range-dependent underwater acoustic waveguide. Our attention is focused on sensitivity of ray dynamics to the vertical structure of a sound-speed perturbation induced by ocean internal waves. Two models of longitudinal sound-speed variations are considered: a periodic inhomogeneity and a stochastic one. It is found that vertical oscillations of a sound-speed perturbation can affect rays in a resonant manner. Such resonances give rise to chaos in certain regions of phase space. It is shown that stability of steep rays, being observed in experiments, is connected with suppression of resonances in the case of small-scale vertical sound-speed oscillations. 
D.V. Makarov, M.Yu. Uleysky, M.Yu. Martynov