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| Titel |
The portion of the total near-inertial energy flux propagating out of the mixed layer |
| VerfasserIn |
Antonija Rimac, Jin-Song von Storch, Carsten Eden |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098399
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| Publikation (Nr.) |
 EGU/EGU2014-14073.pdf |
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| Zusammenfassung |
| The Near-Inertial (NI) motions that are excited by winds are believed to be an important
source for deep-ocean mixing. About 2 TW of energy, mainly supplied by winds and tides,
are required to create mixing to sustain the global general circulation in the ocean. The global
energy rate from the surface to internal tides was estimated to be 0.9 TW. In contrast, the
quantitative assessment of the NI energy available for deep-ocean mixing and the
portion of the total NI energy flux propagating out of the mixed layer remains to be
clarified.
The portion of the total NI energy flux propagating out of the mixed layer has so far been
studied using realistic ocean models, but with leveled upper ocean of a constant depth (the
Mixed Layer Depth (MLD) was assumed to have the depth of e.g., 150 m). This assumption
cannot give a realistic distribution the MLD because of it’s spatial and temporal variability.
To overcome this difficulty we use spatial structure of the MLD diagnosed from
temperature and salinity fields, using a potential density criterion defined by Levitus
(1982). We analize the oceanic state from January and July 2005 at 1-hourly temporal
resolution.
In our analysis, we use the Max Planck Institute Ocean Model at 10 km horizontal
resolution and 80 vertical levels. We calculate the total NI energy flux propagating out of the
mixed layer as a sum of a vertical energy flux and a projection of a horizontal energy flux at
the MLD. We address these questions: How big is the portion of the total wind-induced NI
energy flux that propagates out of the mixed layer? Can we connect the portion of the total NI
energy flux propagating out of the mixed layer and the wind-power input to NI
motions?
Our results show that the total NI energy flux propagating out of the mixed layer shows a
pronounced maximum in the mid-latitude storm track regions during the winter season for
both months. About 12.9% of the total NI energy flux for January and 8.2% for
July propagates out of the mixed layer. We attribute the lower portion of the NI
energy flux propagating out of the mixed layer during July to MLD deepening (up to
800 m) between 30°-60°S. This strong spatial vertical variability of the MLD at the
Southern Hemisphere is not seen in the Northern Hemisphere during January. Higher
wind-power input to NI motions leads to higher dissipation of the total NI energy flux,
meaning that the vertical shear influences the propagation of the total NI energy. |
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