Evaluating the Global Internal Wave Model IDEMIX Using Finestructure Methods


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Dirk.Olbers [ at ] awi.de

Abstract

Small-scale turbulent mixing affects large-scale ocean processes such as the global overturning circulation but remains unresolvedin ocean models. Since the breaking of internal gravity waves is a major source of this mixing, consistent parameterizations take internal wave energetics into account. The model Internal Wave Dissipation,EnergyandMixing(IDEMIX)predictstheinternalwaveenergy,dissipationrates,anddiapycnal diffusivities based on a simplification of the spectral radiation balance of the wave field and can be used as a mixing module in global numerical simulations. In this study, it is evaluated against finestructure estimates of turbulent dissipation rates derived from Argo float observations. In addition, a novel method to compute internal gravity wave energy from finescale strain information alone is presented and applied. IDEMIX well reproducesthe magnitudeandthelarge-scalevariations ofthe Argo-derived dissipationrateandenergylevel estimates. Deficiencies arise with respect to the detailed vertical structure or the spatial extent of mixing hot spots. This points toward the need to improve the forcing functions in IDEMIX, both by implementing additionalphysicaldetailandbybetterconstrainingtheprocessesalreadyincludedinthemodel.Aprominent example is the energy transfer from the mesoscale eddies to the internal gravity waves, which is identified as an essential contributor to turbulent mixing in idealized simulations but needs to be better understood through the help of numerical, analytical, and observational studies in order to be represented realistically in ocean models.



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ISI/Scopus peer-reviewed
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Published
Eprint ID
45662
DOI 10.1175/JPO-D-16-0204.1

Cite as
Pollmann, F. , Eden, C. and Olbers, D. (2017): Evaluating the Global Internal Wave Model IDEMIX Using Finestructure Methods , Journal of Physical Oceanography, 47 , pp. 2267-2289 . doi: 10.1175/JPO-D-16-0204.1


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