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A new characterization of the turbulent diapycnal diffusivities of mass and momentum in the ocean

TitleA new characterization of the turbulent diapycnal diffusivities of mass and momentum in the ocean
Publication TypeJournal Article
Year of Publication2016
AuthorsSalehipour H., Peltier W.R, Whalen C.B, MacKinnon JA
JournalGeophysical Research Letters
Date Published2016/04
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000375537300043
Keywordscirculation; dissipation; drake passage; internal; mixing efficiency; model; parameterization; prandtl number; simulations; stratified shear flows; waves

The diapycnal diffusivity of mass supported by turbulent events in the ocean interior plays a fundamental role in controlling the global overturning circulation. The conventional representation of this diffusivity, due to Osborn (1980), assumes a constant mixing efficiency. We replace this methodology by a generalized-Osborn formula which involves a mixing efficiency that varies nonmonotonically with at least two nondimensional variables. Using these two variables, we propose dynamic parameterizations for mixing efficiency and turbulent Prandtl number (the latter quantifies the ratio of momentum to mass diapycnal diffusivities) based on the first synthesis of an extensive direct numerical simulation of inhomogeneously stratified shear-induced turbulence. Data from Argo floats are employed to demonstrate the extent of the spatial and statistical variability to be expected in both the diapycnal diffusivities of mass and momentum. We therefore suggest that previous estimates of these important characteristics of the global ocean require reconsideration.

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