INTERNAL TIDES OBSERVED BY AN ACOUSTIC DOPPLER CURRENT PROFILER

Previous studies of Knight Inlet, British Columbia, revealed the prese nce of a strong internal M2 tide. Most of the energy was found to be i n either the first or second dynamic modes. Due to difficulties in sam pling of the surface layer, objective estimates of the distribution of tidal energy and reflection coefficients, until now, have been imposs ible to obtain. During June and July 1989, an intense acoustic Doppler current profiler (ADCP) sampling of the inlet was conducted. These re sults are used to show the existence of a strong semidiurnal flow in t he baroclinic field. The authors propose that the horizontal phase inf ormation inherent in the spatial sampling by the ADCP can be used to r esolve the distribution of energy between dynamic modes. Through a lea st squares fit of the data to a simple free wave propagation model of the inlet, the authors arrive at objective estimates of the distributi on of M2 internal tide energy. The fitting procedure is found to be se nsitive to fluctuations in the basin width. When an accurate estimate of width is incorporated into the fit, the authors arrive at net energ y fluxes of 0.44 X 10(6) W toward the mouth of the inlet at Protection Point and 1.17 X 10(6) W toward the head of the inlet at Tomakstum Is land. It is shown that these results do not display the degeneracy inh erent in other estimates and that they are in agreement with a recent numerical model of the inlet by Stacey and Pond.