A baroclinic tide in the eastern North Pacific determined from 1000-km acoustic transmissions

In the summer of 1989 a 1000-km acoustic experiment in the eastern North Pacific showed a semidiurnal variation in pulse travel time that was coherent in depth and varied systematically across time fronts. The effect of a single-plane wave, gravest mode, M sub(2), internal tide has been examined by ray tracing and has been found to show the same characteristic variation as the data if the internal tide is coming from the direction of the Gulf of Alaska. The most reasonable fit corresponds to an energy flux of 800 W m super(-1); implications for tidal dissipation are discussed. In the process of fitting specific acoustic data, the authors have developed an analysis technique for low-mode internal tides that can be applied generally to any acoustic tomography experiment.