Jamshidi, Sean;
(2021)
The vorticity dynamics of coastal currents and outflows.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
This thesis is concerned with the interaction between an along-shore coastal current and flow driven by a jump in potential vorticity. In particular, we develop and apply idealised models for a river outflow, a potential vorticity front, and waves generated by changes in continental-shelf width. In all cases the model ocean has one active layer with piecewise-uniform potential vorticity, and analytic progress is made by assuming the flow varies slowly in the along-shore direction. The behaviour of the model depends strongly on whether the vorticity dynamics reinforce or oppose the coastal current, and on the relative strengths of these two effects. In the outflow model, vorticity is generated by stretching or squashing of fluid columns as they leave the source and adjust to the depth of the upper ocean layer. We explore how this basic mechanism affects the behaviour of the outflow plume by extending the quasi-geostrophic model of Johnson et al (2017). In chapter 2, we extend Johnson et al.'s model to order-one Rossby number using the semi-geostrophic equations, and show that the same range of behaviours occurs. In chapter 3 we allow the potential vorticity of the outflow to vary in space, and show that the behaviour of the resulting plume depends on the net contribution of vorticity at the source. Chapter 4 considers free waves on a potential vorticity front, and shows how they are affected by the presence of a coast. The evolution of the front is described by a nonlinear finite-amplitude equation including first-order dispersive effects, which is analysed using `dispersive shock-fitting’ El (2005). Chapter 5 extends this model to include the continental shelf, and shows that the flow can become hydraulically controlled when the background current opposes coastal-trapped wave propagation.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | The vorticity dynamics of coastal currents and outflows |
| Event: | UCL (University College London) |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| Keywords: | fluid dynamics, geophysical fluid dynamics, applied mathematics |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10119257 |
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