Lee waves and wake generated by a steady current passing over a spherical cap, comparing linear, numerical and experimental approaches
The sources of fluid mixing in the deep ocean have been chased for many years as mixing stands among the key contributors of the meridional ocean circulation. Mixing permits indeed the raising of the deep cold water masses resulting from cold water sinking at high latitudes in the winter hemispheres...
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| Other Authors: | , , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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HAL CCSD
2020
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| Subjects: | |
| Online Access: | https://theses.hal.science/tel-03099430 https://theses.hal.science/tel-03099430/document https://theses.hal.science/tel-03099430/file/GARCIA_MOLINA_2020_archivage.pdf |
| Summary: | The sources of fluid mixing in the deep ocean have been chased for many years as mixing stands among the key contributors of the meridional ocean circulation. Mixing permits indeed the raising of the deep cold water masses resulting from cold water sinking at high latitudes in the winter hemispheres. For about twenty years now, internal gravity waves have been suspected to play a major role in mixing processes. Up to the beginning of the millenium, the main internal gravity wave sources in the ocean were thought to be the tide, by interaction with bottom topography, and surface wind stress. Recent field campaigns in the deep Southern Ocean have actually revealed that the interaction of the Antarctic Circumpolar Current with bottom topography can radiate an internal gravity wave field, referred to as lee waves, as does the wind blowing over a mountain in the atmosphere (Naveira-Garabato et al. 2004, Nikurashin & Ferrari 2010). The field measurements suggest that, over rough topography, these lee waves play a key role in momentum transport and in fluid mixing through their breaking (Sheen et al. 2013). However, deep ocean measurements are sparse (and quite challenging in this part of the ocean) so that the view on mixing processes in the Southern Ocean is still very incomplete. Indeed, if the bottom topography acts as a barrier, the current will be forced to flow over that topography and, depending upon the parameters, a substantial lee wave field may be generated. By contrast, for an isolated three-dimensional topography, part of the current will flow around the topography, thereby generating a wake, with possibly little -or even no- energy transferred to the wave field (Nikurashin et al 2013). The estimate of fluid mixing in the water column by a current flowing over a topography therefore also builds upon how the energy of the current is dissipated : wake or waves. This problem has never been addressed and is the purpose of the present PhD work, using complementary laboratory experiments and numerical ... |
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