Numerical studies of the effect of shelf-edge topography on the stability of along-slope currents
Numerical studies of the effect of shelf-edge topography on the stability of along-slope currents
The rate at which chemical constituents are transferred from the shelf to the deep ocean is controlled by the physical processes occurring at the shelf edge. Understanding these processes and their possible impacts on shelf/ocean exchange is important for dispersion of pollutants, exchange of nutrients and biota between the shelf and ocean, and may be an important factor in the global carbon cycle.
A major component of the exchange is accomplished by the actions of unsteady motions, in particular mesoscale eddies. One possible generation mechanism of such eddies is the instability of currents which flow along the continental slope and shelf edge. Instability can lead to current meandering and detachment of eddies; if the water contained in these eddies originates from the other side of the current then the whole process acts to exchange shelf, slope and deep ocean waters.
This thesis describes work undertaken to investigate the effects of shelf edge topography on the stability of currents along the shelf edge. One- and two-layer ocean models are used to study linear and nonlinear barotropic and baroclinic instability with particular emphasis on the stabilising effects of the topography and the transport between the shelf and ocean. Linear stability analyses determine the conditions for stability and describe the growth of infinitesimal disturbances; nonlinear numerical models illustrate the growth of these disturbances to finite amplitude. Previous work has tended to concentrate on isolated cases with only a few parameter combinations considered; here the emphasis is on systematically varying parameters representing jet strength, topographic slope and stratification.
The typical lifecycle of an unstable jet can be divided into three periods. (1) initial growth of the most linearly-unstable perturbation, (2) growth at finite amplitude, when the nonlinear terms are important, leads to meandering and the rolling up of relative vorticity into discrete eddies, and (3) motion of the eddies as described by vortex dynamics, taking into account vortex stretching.
University of Southampton
1998
Thomas, Ian Martin
(1998)
Numerical studies of the effect of shelf-edge topography on the stability of along-slope currents.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The rate at which chemical constituents are transferred from the shelf to the deep ocean is controlled by the physical processes occurring at the shelf edge. Understanding these processes and their possible impacts on shelf/ocean exchange is important for dispersion of pollutants, exchange of nutrients and biota between the shelf and ocean, and may be an important factor in the global carbon cycle.
A major component of the exchange is accomplished by the actions of unsteady motions, in particular mesoscale eddies. One possible generation mechanism of such eddies is the instability of currents which flow along the continental slope and shelf edge. Instability can lead to current meandering and detachment of eddies; if the water contained in these eddies originates from the other side of the current then the whole process acts to exchange shelf, slope and deep ocean waters.
This thesis describes work undertaken to investigate the effects of shelf edge topography on the stability of currents along the shelf edge. One- and two-layer ocean models are used to study linear and nonlinear barotropic and baroclinic instability with particular emphasis on the stabilising effects of the topography and the transport between the shelf and ocean. Linear stability analyses determine the conditions for stability and describe the growth of infinitesimal disturbances; nonlinear numerical models illustrate the growth of these disturbances to finite amplitude. Previous work has tended to concentrate on isolated cases with only a few parameter combinations considered; here the emphasis is on systematically varying parameters representing jet strength, topographic slope and stratification.
The typical lifecycle of an unstable jet can be divided into three periods. (1) initial growth of the most linearly-unstable perturbation, (2) growth at finite amplitude, when the nonlinear terms are important, leads to meandering and the rolling up of relative vorticity into discrete eddies, and (3) motion of the eddies as described by vortex dynamics, taking into account vortex stretching.
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Published date: 1998
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Local EPrints ID: 463317
URI: http://eprints.soton.ac.uk/id/eprint/463317
PURE UUID: 2c741076-908e-45a8-81db-c220adb51c96
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Date deposited: 04 Jul 2022 20:49
Last modified: 04 Jul 2022 20:49
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Author:
Ian Martin Thomas
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