A model study of spin-down and circulation in a cold water dome |
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Authors: | Jiuxing Xing Alan M Davies |
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Institution: | (1) Proudman Oceanographic Laboratory, 6 Brownlow Street, Liverpool, England, L3 5DA, UK |
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Abstract: | A three-dimensional prognostic hydrodynamic model in cross sectional form is used to examine the influence of bottom friction,
mixing and topography upon the spin-down and steady-state circulation in a cold water bottom-dome. Parameters characteristic
of the Irish Sea or Yellow Sea cold water domes are used. In all calculations, motion is induced by specifying an initial
temperature distribution characteristic of the dome, and an associated along frontal flow. The spin-down of the dome is found
to be influenced by the coefficient of bottom friction, with a typical time scale of order 10 days, and in general to be independent
of the chosen initial vertical profile of along frontal flow. However, in the case in which the along frontal flow is such
that the near bed velocity is zero, then bottom stress is also zero, and there is no appreciable spin-down. Calculations showed
that the formulation of viscosity and diffusivity had a greater effect upon the steady-state circulation than topography,
suggesting that background mixing of tidal origin is important. The lack of topographic influence was due mainly to the formulation
of the initial conditions which were taken to be independent of topography. The steady-state circulation was characterized
by a cyclonic flow in the surface region, with an anti-cyclonic current near the bed, where frictional effects produced a
bottom Ekman layer and an across frontal flow. This gave rise to vertical circulation cells in the frontal region of the dome
with prevailing downwelling motion inside the dome. A detailed analysis of the dynamic balance of the various terms in the
hydrodynamic equations yielded insight into the processes controlling the steady-state circulation in cold water domes.
Responsible Editor: Phil Dyke |
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Keywords: | Topography Mixing Bottom friction Spin-down Circulation Bottom-dome Irish Sea Yellow Sea |
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