UBC Theses and Dissertations
Internal solitary waves in Davis Strait Cummins, Patrick
Current meters and a thermistor chain deployed in proximity of a drillship over the continental shelf off Baffin Island revealed the presence of large amplitude internal waves. This thesis reviews properties of the internal waves, observed to propagate away from the coast and to coincide with the local low water phase of the tide, at the drillship. The waves were characterized by a sudden pulse-like increase in current speed and a rapid depression of isotherms suggestive of internal solitary waves. Measurements of propagation time indicate phase speeds of 1.1 m/s are typical with horizontal length scales comparable to the total fluid depth. An analysis based on linear internal wave theory and involving the solution of the vertical eigenfunction was found to fit the measured wave characteristics poorly. A nonlinear wave analysis, based on the Korteweg-de Vries equation and employing the vertical eigenfunction, gave better results. Wave profiles are correctly given by the solitary wave solution of the KdV equation. The relation between amplitude and phase speed indicates that the advection due to the tidal flow is important. The length of the disturbances is underpredicted by the theory at large amplitudes. Calculations of Richardson number using the wave-induced shear show that shear instabilities are likely to occur.
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