NOTES AND CORRESPONDENCE Dissipative Losses in Nonlinear Internal Waves Propagating across the Continental Shelf

A single nonlinear internal wave tracked more than 100 wavelengths across Oregon’s continental shelf over a 12-h period exhibited nearly constant wave speed, c 0.75 m s , and amplitude, a 15 m. The wavelength L gradually decreased from 220 m in 170-m water depth to 60 m in 70-m water depth. As the water shallowed beyond 50 m, the wave became unrecognizable as such. The total energy decreased from 1.1 to 0.5 MJ m . The rate at which wave energy was lost, dE /dt 14 [7, 22] W m , was approximately equal to the energy lost to turbulence dissipation, 10 [7, 14] W m , as inferred from turbulence measurements in the wave cores plus estimates in the wave-induced bottom boundary layer. The approximate balance, dE/dt , differs from the solibore model of Henyey and Hoering in which the potential energy across the wave balances . However, other evidence suggests that the wave evolved from a solibore-like state to a dissipative solitary wavelike state over the observed propagation path.