Shoaling internal solitary waves

Blokhina, Marina (2009) Shoaling internal solitary waves. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Internal solitary waves are encountered throughout the ocean and are a key part of coastal water dynamics. With the theoretical basis developed for infinitesimally small weakly-nonlinear waves several decades ago and a fully nonlinear theory still under development, internal waves remain on the front edge of ocean science. -- In the present study, properties of high-frequency internal solitary waves propagating in a shallow water environment are studied using both field observations and numerical simulations. An array of bottom moorings and shipboard instruments are used to track internal wave packets propagating towards the flank of the Ile-aux-Lievres Island (St. Lawrence Estuary). The transformation leading to dissipation of a wave of depression into a number of waves of elevation is documented. The observed spatio-temporal wave characteristics are compared to the first-order Korteveg-de Vries theory and a fully nonlinear two-layer theory. -- High resolution two-dimensional nonhydrostatic numerical simulations are performed to supplement the field observations. The focus is on the properties of internal waves of elevation (often referred to as boluses) resulting from the shoaling of the wave of depression onto a linear slope. A hypothesis that boluses play a significant role in mass transport is tested. -- This work contributes to better understanding of the mechanisms of internal wave shoaling over linear slopes. The formation of the trapped cores inside waves of elevation is demonstrated using nonhydrostatic numerical simulations. To our knowledge this is a novel result which helps to explain field and laboratory observations of trapped cores. The detailed study of the transport properties of waves of elevation is also done. A simple parametrization of the mass transport caused by waves of elevation is proposed.

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