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| Cimoli, Laura; Caulfield, Colm‐cille P.; Johnson, Helen L.; Marshall, David P.; Mashayek, Ali; Naveira Garabato, Alberto C.; Vic, Clement. |
| There have been recent advancements in the quantification of parameters describing the proportion of internal tide energy being dissipated locally and the “efficiency” of diapycnal mixing, i.e. the ratio of the diapycnal mixing rate to the kinetic energy dissipation rate. We show that oceanic tidal mixing is non‐trivially sensitive to the co‐variation of these parameters. Varying these parameters one at the time can lead to significant errors in the patterns of diapycnal mixing driven upwelling and downwelling, and to the over and under estimation of mixing in such a way that the net rate of globally‐integrated deep circulation appears reasonable. However, the local rates of upwelling and downwelling in the deep ocean are significantly different when both... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00595/70675/68873.pdf |
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| Vic, Clement; Naveira Garabato, Alberto C.; Green, J. A. Mattias; Waterhouse, Amy F.; Zhao, Zhongxiang; Melet, Angelique; De Lavergne, Casimir; Buijsman, Maarten C.; Stephenson, Gordon R.. |
| Turbulent mixing in the ocean is key to regulate the transport of heat, freshwater and biogeochemical tracers, with strong implications for Earth's climate. In the deep ocean, tides supply much of the mechanical energy required to sustain mixing via the generation of internal waves, known as internal tides, whose fate-the relative importance of their local versus remote breaking into turbulence-remains uncertain. Here, we combine a semi-analytical model of internal tide generation with satellite and in situ measurements to show that from an energetic viewpoint, small-scale internal tides, hitherto overlooked, account for the bulk (>50%) of global internal tide generation, breaking and mixing. Furthermore, we unveil the pronounced geographical variations... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00601/71275/69674.pdf |
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| Yu, Xiaolong; Naveira Garabato, Alberto C.; Martin, Adrian P; Evans, D. Gwyn; Su, Zhan. |
| Mooring and glider observations and a high‐resolution satellite sea surface temperature image reveal features of a transient submesoscale front in a typical mid‐ocean region of the Northeast Atlantic. Analysis of the observations suggests that the front is forced by downfront winds and undergoes symmetric instability, resulting in elevated upper‐ocean kinetic energy, re‐stratification and turbulent dissipation. The instability is triggered as downfront winds act on weak upper‐ocean vertical stratification and strong lateral stratification produced by mesoscale frontogenesis. The instability's estimated rate of kinetic energy extraction from the front accounts for the difference between the measured rate of turbulent dissipation and the predicted... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00514/62521/66828.pdf |
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| Yu, Xiaolong; Naveira Garabato, Alberto C.; Martin, Adrian P; Buckingham, Christian; Brannigan, Liam; Su, Zhan. |
| Numerical simulations suggest that submesoscale turbulence may transform lateral buoyancy gradients into vertical stratification, and thus restratify the upper ocean via vertical flow. However, the observational evidence for this restratifying process has been lacking due to the difficulty in measuring such ephemeral phenomena, particularly over periods of months to years. This study presents an annual cycle of the vertical velocity and associated restratification estimated from two nested clusters of meso- and submesoscale-resolving moorings, deployed in a typical mid-ocean area of the Northeast Atlantic. Vertical velocities inferred using the non-diffusive density equation are substantially stronger at submesoscales (horizontal scales of 1-10 km) than at... |
| Tipo: Text |
Palavras-chave: Ocean; Atlantic Ocean; Ageostrophic circulations; Frontogenesis; Frontolysis; In situ oceanic observations. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00489/60076/63398.pdf |
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