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Modelling of partially-resolved oceanic symmetric instability


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Type

Article

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Authors

Bachman, SD 
Taylor, JR 

Abstract

A series of idealized numerical models have been developed to investigate the effects of partially resolved symmetric instability (SI) in oceanic general circulation models. An analysis of the energetics of symmetric instability is used to argue that the mixed layer can be at least partially restratified even when some SI modes are absent due to either large horizontal viscosity or coarse model resolution. Linear stability analysis reveals that in the idealized models the amount of restratification can be predicted as a function of the grid spacing and viscosity. The models themselves are used to demonstrate these predictions and reveal three possible outcomes in steady-state: (1) incomplete restratification due to viscosity, (2) incomplete restratification due to resolution, and (3) excessive restratification due to anisotropy of the viscosity. The third outcome occurs even on a high-resolution isotropic grid and in two separate numerical models, and thus appears to be a sort of robust numerical feature. The three outcomes are used to recommend criteria that a successful SI parameterization should satisfy.

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Keywords

Symmetric instability, Ocean modeling, Mixed layer, Restratification, Submesoscale, Eddies

Journal Title

Ocean Modelling

Conference Name

Journal ISSN

1463-5003
1463-5011

Volume Title

82

Publisher

Elsevier BV
Sponsorship
Natural Environment Research Council (NE/J010472/1)
The authors gratefully acknowledge support from the Natural Environment Research Council, award NE/J010472/1.