| Summary: | Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution April, 1975 This thesis reports on an investigation into the structure, energetics and propagation of tidal frequency internal waves. Data from Site D, near the New England continental slope, Muir Seamount northeast of Bermuda, and the Mid-Ocean Dynamics Experiment in the deep Sargasso Sea were used. Site D, in the near-field of a near-critical semidiurnal generation region, shows variable tidal currents and a marked surface intensification of M2 energy at the southern Site, related to the beam-like nature of the internal tide. The M2 tide dominates the semidiurnal band, with about 3 times more energy than at adjacent frequencies at 1/15 cpd separation. There is a significant phase locking between the M2 baroclinic currents and the equilibrium tide, and evidence for southward propagation of internal wave energy, suggesting generation at the slope to the north. The M2 baroclinic energy density is about 40% as great as the total barotropic energy density, but the internal tides have more horizontal kinetic energy. A seaward energy flux of .6 x 106 erg/s cm in the first three baroclinic M2 modes is much less than the .2 x 1010 erg/s cm shoreward energy flux in the surface tide. Difficul ties in interpreting the measurements are ascribed to the near-singular generation case. The MODE-l semidiurnal internal tides are also dominated by the M2 frequency, with a 3-fold energy increase over adjacent frequencies at 1/15 cpd separation. MODE-l is far from any major source of internal tides, but the measurements are much less variable than those from Site D. The extensive temperature measurements defining the MODE-l M2 internal tide are significantly coherent (phase locked) with the equilibrium tide, with about 80% of the coherent energy deriving from the first baroclinic mode, typical thermocline displacements being 3 m. A horizontal ...
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