Horizontal dispersion within the stratified interior of coastal shelf waters
Abstract/Contents
- Abstract
- Horizontal transport and dispersion on the continental shelf are important for understanding the distributions of nutrients, contaminants, biological aggregates, and other scalars in the coastal environment. The hydrodynamic mechanisms leading to transport and dispersion are often not well understood, owing to variability in forcing conditions and scale-dependent behavior. The main goal of this dissertation is to address how complex shelf dynamics lead to horizontal dispersion. To this end, we conducted several field, analytical, and numerical experiments. Field research involved autonomous underwater vehicle measurements to quantify horizontal dispersion of a continuously released Rhodamine WT dye plume within the stratified interior of northern Monterey Bay, CA. The observed spreading of the dye plume provides evidence for scale-dependent dispersion. An analytical shear-flow dispersion model and a numerical particle-tracking model also provide estimates of the lateral dispersion and agree with the field measurements. Another goal of this dissertation is to assess and quantify the effects of shear flow dispersion in steady, oscillatory, and combined shear fields. We demonstrate that the horizontal variance of a point source release is a function of three contributions: a steady shear term responsible for time-cubed growth, an oscillatory shear term subject to long-term linear in time growth, and an interaction term accountable for increasingly negative oscillations in time. A primary finding of this work is that dispersion is strongly related to the ratio of the steady and oscillatory shear amplitudes, and the time non-dimensionalized by the oscillatory shear frequency. When oscillatory shear dominates, the interaction term is particularly important to determine the variance growth behavior. Additionally, temporal variability in vertical turbulent diffusivity generates long-term effects on variance growth. The particle-tracking model is used to evaluate horizontal shear dispersion over the summer upwelling season. Shear within the stratified interior is generally characterized by dominantly diurnal to semi-diurnal oscillations and high frequency oscillations (~15-30 minutes) due to internal waves. The modeled dispersion over 2, 6, and 12 hours is scale-dependent and sensitive to both the time of release relative to the shear phase and the integration time. Additionally, we find that the dispersion is well modeled using the measured vertical shear structure with a constant vertical turbulent diffusivity over the sampling time.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2013 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Moniz, Ryan Joseph |
|---|---|
| Associated with | Stanford University, Department of Civil and Environmental Engineering. |
| Primary advisor | Monismith, Stephen Gene |
| Thesis advisor | Monismith, Stephen Gene |
| Thesis advisor | Fong, Derek |
| Thesis advisor | Fringer, Oliver B. (Oliver Bartlett) |
| Thesis advisor | Koseff, Jeffrey Russell |
| Advisor | Fong, Derek |
| Advisor | Fringer, Oliver B. (Oliver Bartlett) |
| Advisor | Koseff, Jeffrey Russell |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Ryan Joseph Moniz. |
|---|---|
| Note | Submitted to the Department of Civil and Environmental Engineering. |
| Thesis | Ph.D. Stanford University 2013 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2013 by Ryan Joseph Moniz
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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