Interfacial internal waves impacting sloped boundaries.

摘要

When interfacial internal waves shoal over a sloped bottom, a fraction of the wave energy is reflected from the boundary, with the rest being diverted into other processes such as transport, dissipation, and mixing. In this thesis, I develop techniques to infer the variability of this energy partitioning due to wave shoaling from common oceanographic measurements.;To apply gamma in the field, it is necessary to determine the angle at which the waves approach the slope. For internal waves propagating across a vertically sheared flow, wave-heaving of the flow masks wave velocities, hindering inference of wave propagation direction. A technique to infer wave propagation direction in such situations is presented and shown to be superior to other techniques.;The influence of a vertically sheared background flow on wave shoaling is considered by examining field observations in which waves generate boluses of dense fluid that propagate upslope. It is demonstrated that these boluses contain a component of the cross-wave background flow. A bolus decay model suggests that the additional velocity of the fluid within the bolus does not enhance mixing.;Wave mixing efficiencies from previously published laboratory experiments of shoaling solitary internal waves are used to estimate a relationship between mixing and gamma. Using a two-week time series of acoustic Doppler current profiler data, a gamma-based parameterization of wave-induced mixing is developed for the Upper Saint Lawrence Estuary. It is suggested that at this location, wave-induced mixing and shear-induced mixing are of equal importance over a spring-neap tidal cycle.;This work introduces a new acceleration-based shoaling parameter gamma, which is a measure of the interfacial acceleration across the bottom slope relative to gravitational acceleration projected onto the slope. Using wave energy reflectance R as a test metric, the utility of gamma is compared that of the Iribarren number. Previously published shoaling surface wave experiments and new two-dimensional numerical simulations of nonlinear interfacial wave shoaling are used to show that gamma-R relationships for surface and internal wave groups are comparable.