Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1984. / Vita. Bibliography: p. 200-206.

Internal waves in lakes and oceans are ubiquitous whenever a density stratification is present. These waves are relatively slow moving, can be large in extent and have long time scales. As these waves are so common, it is suspected that they play a role in recirculating nutrients throughout the water column. The various factors contributing to this recirculation are commonly referred to as the nutrient circulation system. This thesis analyses three potential mechanisms of internal wave forcing of the nutrient circulation system over a range of length scales. Namely, we discuss internal wave shear induced sediment resuspension, non-Newtonian fluid mud vortex dynamics and internal wave forced lake bottom seepage. We believe that these demonstrate the significant effect that internal waves can have on distributing nutrients throughout the water column. In conjunction, these mechanisms have the potential to be the dominant source of nutrient circulation in certain regions of lakes and oceans.

Internal waves in the deep ocean play a deciding role in processes such as climate change and nutrient cycles. Winds and tidal currents over topography feed energy into internal waves at large scales; through nonlinear interaction the energy then cascades to turbulence scales and contributes to deep-ocean mixing. The connection of internal waves to deep-ocean mixing is what makes them important. In this thesis we address the problem of energy transfer in internal waves by modelling a two-dimensional flow over idealized topography and analysing the spectra of the generated wave fields. The main tool used is the nonparametric spectral analysis, some aspects of which are reviewed in one of the chapters. The numerical experiments were performed for a number of latitudes, topographies and background flows. The wave field generated by tide-topography interaction includes both progressive and trapped internal waves. The wave spectrum was found to exhibit a self-similar structure with prominent peaks at tidal harmonics and interharmonics, whose magnitudes decay exponentially as a function of the frequency. Subharmonics are generated by an instability of tidal beams, which is particularly strong for near-critical latitudes, where the Coriolis frequency is half the tidal frequency; other interharmonics are produced through resonant and non-resonant triad wave-wave interaction. As the triad interaction can be either resonant or non-resonant, some harmonics and interharmonics correspond to progressive waves, if the frequency is within the free internal wave range, while the others are trapped waves if the frequency is outside the range. Spatial scales of harmonics and interharmonics were investigated. In particular, it was shown that interharmonics typically have smaller vertical scales. Through the use of spatial analysis it was shown that there is a discrete number of wave-wave interactions responsible for the total energy transfer. The results of the thesis provide insight into the complex nature of internal wave interactions and may be helpful for interpreting recent observational results.

Internal waves in the deep ocean play a deciding role in processes such as climate change and nutrient cycles. Winds and tidal currents over topography feed energy into internal waves at large scales; through nonlinear interaction the energy then cascades to turbulence scales and contributes to deep-ocean mixing. The connection of internal waves to deep-ocean mixing is what makes them important. In this thesis we address the problem of energy transfer in internal waves by modelling a two-dimensional flow over idealized topography and analysing the spectra of the generated wave fields. The main tool used is the nonparametric spectral analysis, some aspects of which are reviewed in one of the chapters. The numerical experiments were performed for a number of latitudes, topographies and background flows. The wave field generated by tide-topography interaction includes both progressive and trapped internal waves. The wave spectrum was found to exhibit a self-similar structure with prominent peaks at tidal harmonics and interharmonics, whose magnitudes decay exponentially as a function of the frequency. Subharmonics are generated by an instability of tidal beams, which is particularly strong for near-critical latitudes, where the Coriolis frequency is half the tidal frequency; other interharmonics are produced through resonant and non-resonant triad wave-wave interaction. As the triad interaction can be either resonant or non-resonant, some harmonics and interharmonics correspond to progressive waves, if the frequency is within the free internal wave range, while the others are trapped waves if the frequency is outside the range. Spatial scales of harmonics and interharmonics were investigated. In particular, it was shown that interharmonics typically have smaller vertical scales. Through the use of spatial analysis it was shown that there is a discrete number of wave-wave interactions responsible for the total energy transfer. The results of the thesis provide insight into the complex nature of internal wave interactions and may be helpful for interpreting recent observational results.

Abstract Internal waves have been identified as one of the most active mechanisms producing vertical mixing in continental slope and shelf waters. The major contribution of mixing are due to internal tides, however, shorter period internal waves are unlikely to be the main source of energy for mixing, especially on the inner part of the continental shelf. In this study, we observe the vertical mixing of huge internal waves in the Dongsha Atoll South China Sea. These solitary waves were originate near the Luzon Strait, propagated westward across the basin, evolving into internal solitary wave trains and dissipated at the western shallow continental shelf. The wave energy and phase speed reduced significantly during the shoaling process. Internal waves and their likely related induced mixing phenomena are analyzed based on multiple cruises of observations consisted of CTD hydrographic measurements, water samples and moored thermister strings. Data analyses show that the mixing processes are related to depths of water and the interfacial of wave. For depression wave in the deep water zone, upper layer water may push downward producing vertical mixing beyond the thermocline. The mixing usually dilutes the nutrients in the upper layer of water column. Statistics suggest that the N:P ratio is 12:1 which is lower than the standard value (16:1) indicating the region is nitrogen deficit, similar to most of the surface water in South China Sea. The depression solitons in deep water may evolved to a packet of elevation waves in the shallow water area at ¡§turning point¡¨ of approximately equal depth of upper and lower layers. The mixing of shallow water internal waves can entrain cold nutrient rich water from the lower layer into the frequently nutrient depleted subsurface layer to enhance the local coral reef ecosystem. For example, CTD profiles (2008.5.7) before and after the passage of internal wave show large differences. The vertical density distribution has dramatic change. The column was stratified in two layers in normal condition. The internal waves perturbed the water column into stepwise multi-layer density distribution. The water at 50 m showed temperature decrease by 6 ¢J, salinity increase by 23 psu, density increase by 1.8 , fluorescence decrease by 0.065 £gg/L etc. The MODIS chlorophyll images confirm the high concentration fertilized by the internal wave pumping near the NE region of the Dongsha Atoll.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 46-49). Also available on the World Wide Web.

Thesis (M. Sc.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on Jan. 15, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Physics, University of Alberta. Includes bibliographical references.

Thesis (M. Sc.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on Jan. 21, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Applied Mathematics, Department of Mathematical and Statistical Sciences. Includes bibliographical references.

In the ocean, internal gravity waves are generated by tidal flow over sea floor topography. An internal gravity wave is only able to freely propagate if the buoyancy frequency is greater than the driving frequency, where the buoyancy frequency is proportional to the square root of the density gradient. A turning depth is defined as a height below which the buoyancy frequency is less than the driving frequency. King et al. showed that turning depths for internal waves generated by lunar tidal flow exist in the ocean, at varying heights from the sea floor [11]. The present study is the first to examine the generation and propagation of internal waves by tidal flow over topography that lies below a turning depth. I use laboratory experiments and numerical simulations to examine the effect of these turning depths on energy flux of the internal waves generated by tidal flow over topography. I find excellent agreement between numerical and laboratory work, and I show that the internal wave energy is strongly damped by the presence of a turning depth above the topography. Further, this has strong implications for ocean energy budget calculations. / text

Internal waves are generated in the ocean by oscillating tidal flow over bottom topography such as ridges, seamounts, and continental slopes. They are similar to the more familiar surface waves, but not being constrained to move on the surface, propagate throughout the bulk of the world oceans. Internal waves transmit energy over thousands of kilometers, ultimately breaking and releasing their energy into turbulence and mixing. Where these internal waves are generated, as well as where and how they break and cause mixing, has important effects on the general circulation of the ocean, which is in turn a major component in earth's climate. As a first step in a more thorough understanding of the evolution of internal waves in the ocean, it is important to characterize their generation. The two-dimensional generation problem has been studied for four decades, with ample experimental, numerical, and theoretical results. Most of this past work has also been done using linear, inviscid approximations. However, wave generation in the ocean is three-dimensional (3D), and in many locations, nonlinear and viscous effects can be significant. Recent advances in experimental and numerical techniques are only now making the fully nonlinear, 3D generation process accessible. We utilize these new techniques to perform both laboratory experiments and numerical simulations on internal wave generation in 3D. We find that a significant component of the internal wave field generated by tidal flow over 3D topography is radiated in the direction perpendicular to the tidal forcing direction. This could lead to substantial improvements of global internal wave generation models. In addition, we have developed a new method for statistical analysis of ocean data sets, and have found large regions in the deep ocean where internal waves may not propagate. This will also have important effects on the way researchers study the propagation of internal waves, which, when propagating downward, were previously thought to always reflect from the sea floor. / text