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Spin-up over steep topography and the effects of a submarine canyon Mirshak, Ramzi
Abstract
Submarine canyons are common bathymetric features that cut into the continental shelf from the continental slope. During upwelling favourable conditions over the continental shelf, submarine canyons display enhanced upwelling, heavily impacting shelf-slope mass exchange. In this thesis, laboratory experiments were conducted to quantify how velocity, stratification and rotation affect canyon upwelling. Currents were forced by changing the rotation rate of an already rotating tank. Over time, the forced currents evolve, or spin-up, until the fluid within the tank is once again rotating at the same rate as the tank itself. A difference in the spin-up behaviour is observed when a canyon is not present in the laboratory topography. The dynamics that govern flow evolution when a canyon is not present are Ekman suction and diffusion, both of which can be affected by a sloped bottom boundary layer. A numerical model is developed that replicates the spin-up of a stratified fluid over the changing slopes of the laboratory topography in the absence of a canyon, incorporating both the decay of Ekman suction and the change in the diffusion of momentum which occur as the boundary layer flow is arrested by buoyancy effects. Observed spin-up with a canyon present is compared to predicted spin-up without a canyon. The difference measures a force imposed by the canyon, which is found to be proportional to U[sup 2.5]f[sup 0.5]/N, where U is the shelfbreak velocity, f is the Coriolis frequency and N is the buoyancy frequency. This force relates to the flux of water crossing the shelfbreak through the canyon. The results are applied to Astoria canyon, suggesting that in a strong upwelling event, the flux of water through the canyon is 1.3 x 10 ⁵m³ s⁻¹ , nearly 20 times larger than wind-induced upwelling over a similar length of the shelfbreak.
Item Metadata
Title |
Spin-up over steep topography and the effects of a submarine canyon
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2001
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Description |
Submarine canyons are common bathymetric features that cut into the continental
shelf from the continental slope. During upwelling favourable conditions over the continental
shelf, submarine canyons display enhanced upwelling, heavily impacting shelf-slope
mass exchange. In this thesis, laboratory experiments were conducted to quantify how
velocity, stratification and rotation affect canyon upwelling.
Currents were forced by changing the rotation rate of an already rotating tank. Over
time, the forced currents evolve, or spin-up, until the fluid within the tank is once again
rotating at the same rate as the tank itself. A difference in the spin-up behaviour is
observed when a canyon is not present in the laboratory topography. The dynamics that
govern flow evolution when a canyon is not present are Ekman suction and diffusion,
both of which can be affected by a sloped bottom boundary layer. A numerical model is
developed that replicates the spin-up of a stratified fluid over the changing slopes of the
laboratory topography in the absence of a canyon, incorporating both the decay of Ekman
suction and the change in the diffusion of momentum which occur as the boundary layer
flow is arrested by buoyancy effects.
Observed spin-up with a canyon present is compared to predicted spin-up without a
canyon. The difference measures a force imposed by the canyon, which is found to be
proportional to U[sup 2.5]f[sup 0.5]/N, where U is the shelfbreak velocity, f is the Coriolis frequency
and N is the buoyancy frequency. This force relates to the flux of water crossing the
shelfbreak through the canyon. The results are applied to Astoria canyon, suggesting that
in a strong upwelling event, the flux of water through the canyon is 1.3 x 10 ⁵m³ s⁻¹ , nearly
20 times larger than wind-induced upwelling over a similar length of the shelfbreak.
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Extent |
4197554 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-08-06
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0052635
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2001-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.