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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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| 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; Ponte, Aurelien; Elipot, Shane; Menemenlis, Dimitris; Zaron, Edward D.; Abernathey, Ryan. |
| The surface kinetic energy of a 1/48° global ocean simulation and its distribution as a function of frequency and location are compared with the one estimated from 15,329 globally distributed surface drifter observations at hourly resolution. These distributions follow similar patterns with a dominant low‐frequency component and well‐defined tidal and near‐inertial peaks globally. Quantitative differences are identified with deficits of low‐frequency energy near the equator (factor 2) and at near‐inertial frequencies (factor 3) and an excess of energy at semidiurnal frequencies (factor 4) for the model. Owing to its hourly resolution and its near‐global spatial coverage, the array of surface drifters is an invaluable tool to evaluate the realism of... |
| Tipo: Text |
Palavras-chave: LLC4320; Surface drifter; Rotary spectrum; SWOT. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00514/62517/66817.pdf |
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| Pan, Huanglei; Yu, Xiaolong; Liu, Dishi; Shi, Dalin; Yang, Shengyun; Pan, Weiran. |
| A physical–biological ocean model was employed to investigate characteristics of the Beibu Gulf in the northwest South China Sea (SCS) from 2011 to 2015. We adopted the spatially constrained multivariate clustering method to determine the refined marine environmental regionalization using 10 variables from the model output, and compared regionalization differences in ENSO (El Niño–Southern Oscillation) years. The simulated physical and biochemical variables display a wide spectrum of patterns in space and time. The regionalization maps indicated that the Qiongzhou Strait and its adjacent area can be classified as a separate region, characterized by the rich presence of nutrients, phytoplankton, zooplankton, and detritus, owing to the water invasion from... |
| Tipo: Text |
Palavras-chave: Beibu Gulf; Physical-biological model; Regionalization; Multivariate clustering; ENSO. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00679/79109/81600.pdf |
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| Yu, Xiaolong; Ponte, Aurelien; Lahaye, Noe; Caspar-cohen, Zoe; Menemenlis, Dimitris. |
| urrent satellite altimeters map sea surface height (SSH) with an effective spatial scale of O(100 km) and, as a result, surface ocean velocity can be appropriately estimated from merged SSH fields by assuming geostrophic equilibrium. The validity of the geostrophic assumption down to the spatial scale of O(10 km) that will be newly resolved by the next generation of satellite altimeters, such as the Surface Water Ocean Topography (SWOT) mission, remains unknown. In this study, the accuracy of geostrophy for the estimation of surface currents from a knowledge of instantaneous sea level is quantified using the hourly fields from a tide- and eddy-resolving global numerical simulation. Geostrophic balance is found to be the leading-order balance in frontal... |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00688/79962/82890.pdf |
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| Erickson, Zachary K; Thompson, Andrew F; Callies, Jörn; Yu, Xiaolong; Naveira Garabato, Alberto; Klein, Patrice. |
| Submesoscale dynamics are typically intensified at boundaries and assumed to weaken below the mixed layer in the open ocean. Here, we assess both the seasonality and the vertical distribution of submesoscale motions in an open ocean region of the northeast Atlantic. Second-order structure functions, or variance in properties separated by distance, are calculated from submesoscale-resolving ocean glider and mooring observations, as well as a 1/48° numerical ocean model. This data set combines a temporal coverage that extends through a full seasonal cycle, a horizontal resolution that captures spatial scales as small as 1 km, and vertical sampling that provides near-continuous coverage over the upper 1000 m. While kinetic and potential energies undergo a... |
| Tipo: Text |
Palavras-chave: Instability; Mixing; Small scale processes; Buoy observations; Profilers; Oceanic. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00592/70388/68470.pdf |
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