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| Titel |
Non-breaking wave induced ocean mixing |
| VerfasserIn |
M. Ghantous, A. Babanin, D. Chalikov |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062314
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| Zusammenfassung |
| Mixing of the upper ocean affects the sea surface temperature by bringing
deeper, colder water to the surface. Even small changes in the surface
temperature can have a large impact on global weather and climate, so it is
critical to determine it accurately for forecasting. Although there are
several mechanisms that can lead to mixing, one that has until recently been
overlooked is the effect of non-breaking, wind-generated surface waves.
In most theoretical models, ocean surface waves are presumed to be
irrotational, since the viscosity of water is small and their motion is not
greatly affected. However this overlooks two important aspects of the motion:
the first is that however small the viscosity, it is not zero; secondly, even
potential wave motion can interact with pre-existing vorticity in the water.
The consequences of this are clear: given large enough waves, the
non-irrotational motion can generate turbulence, and given pre-existing
turbulence, the waves, even when considered as irrotational, transfer their
own energy to the turbulence. Aside from dissipating the waves, this
enhancement of the background turbulence can lead to deeper and more rapid
mixing than might otherwise occur.
Other mechanisms of turbulence generation by surface waves that have been
studied include the interaction of Stokes drift with the turbulence, Langmuir
circulation, and wave breaking. Experimental, observational, modelling and
theoretical work indicates that the last of these only has a very shallow
effect, and the other two are either too weak or too infrequent to account for
the observed mixing. All have to be artificially enhanced in models to
account for the mixing observed. By parameterising the effect of the
turbulence directly generated by the orbital particle motion due to the waves,
the correct rate and depth of mixing can be calculated. Various models
incorporating such a parameterisation have shown closer agreement with
observation than previously achieved, however the parameterisations still need
refinement. We propose one based closely on the physics of the motion,
deriving results from a wave model coupled to a large eddy simulation
turbulence model. |
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