The combined effect of tidally and eddy-driven diapycnal mixing on the large-scale ocean circulation

Saenko, Oleg A., Zhai, Xiaoming, Merryfield, William J. and Lee, Warren G. (2012) The combined effect of tidally and eddy-driven diapycnal mixing on the large-scale ocean circulation. Journal of Physical Oceanography, 42 (4). pp. 526-538. ISSN 0022-3670

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Abstract

Several recent studies have shown that ocean western boundaries are the primary regions of eddy energy dissipation. Globally, the eddy energy sinks have been estimated to integrate to about 0.2 TW. This is a sizable fraction of the tidal energy dissipation in the deep oceanic interior, estimated at about 1.0 TW and contributing to diapycnal mixing. The authors conduct sensitivity experiments with an ocean general circulation model assuming that the eddy energy is scattered into high-wavenumber vertical modes, resulting in energy dissipation and locally enhanced diapycnal mixing. When only the tidal energy dissipation maintains diapycnal mixing, the overturning circulation, and stratification in the deep ocean are too weak. With the addition of the eddy dissipation, the deep-ocean thermal structure becomes closer to that observed and the overturning circulation and stratification in the abyss become stronger. Furthermore, the mixing associated with the eddy dissipation can, on its own, drive a relatively strong overturning. The stratification and overturning in the deep ocean are sensitive to the vertical structure of diapycnal mixing. When most of this energy dissipates within 300 m above the bottom, the abyssal overturning and stratification are too weak. Allowing for the dissipation to penetrate higher in the water column, such as suggested by recent observations, results in stronger stratification and meridional circulation. Zonal circulation is also affected. In particular, the Drake Passage transport becomes closer to its observational estimates with the increase in the vertical scale for turbulence above topography. Consistent with some theoretical models, the Drake Passage transport increases with the increase in the mean upper-ocean diffusivity. © 2012 American Meteorological Society.

Item Type: Article
Uncontrolled Keywords: abyssal circulation,meridional overturning circulation,mixing,general circulation models,parmeterization,subgrid-scale processes
Faculty \ School: Faculty of Science > School of Environmental Sciences
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Depositing User: Users 2731 not found.
Date Deposited: 29 Feb 2012 13:26
Last Modified: 21 Apr 2020 16:52
URI: https://ueaeprints.uea.ac.uk/id/eprint/37668
DOI: 10.1175/JPO-D-11-0122.1

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