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| Cimoli, Laura; Stegner, Alexandre; Roullet, Guillaume. |
| This study investigates the linear and non-linear instability of a buoyant coastal current flowing along a sloping topography. In fact, the bathymetry strongly impacts the formation of meanders or eddies and leads to different dynamical regimes that can both enhance or prevent the cross-shore transport. We use the Regional Ocean Modeling System (ROMS) to run simulations in an idealized channel configuration, using a fixed coastal current structure and testing its unstable evolution for various depths and topographic slopes. The experiments are integrated beyond the linear stage of the instability, since our focus is on the non-linear end state, namely the formation of coastal eddies or meanders, to classify the dynamical regimes. We find three non-linear... |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00410/52187/52915.pdf |
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| Ayouche, Adam; De Marez, Charly; Morvan, Mathieu; L'Hegaret, Pierre; Carton, Xavier; Le Vu, Briac; Stegner, Alexandre. |
| The Ras al Hadd oceanic dipole is a recurrent association of a cyclone (to the northeast) and of an anticyclone (to the southwest), which forms in summer and breaks up at the end of autumn. It lies near the Ras al Hadd cape, southeast of the Arabian peninsula. Its size is on the order of 100 km. Along the axis of this dipole flows an intense jet, the Ras al Had jet. Using altimetric data and an eddy detection and tracking algorithm (AMEDA: Angular Momentum Eddy Detection and tracking Algorithm), we describe the life cycle of this oceanic dipole over a year (2014–2015). We also use the results of a numerical model (HYCOM, the HYbrid Coordinate Ocean Model) simulation, and hydrological data from ARGO profilers, to characterize the vertical structure of the... |
| Tipo: Text |
Palavras-chave: Ras al hadd oceanic dipole; Arabian sea; Cyclonic and anticyclonic eddies; Altimetric data; Angular momentum eddy detection and tracking algorithm (AMEDA); HYCOM model; ARGO floats. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00679/79107/81598.pdf |
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| Caldeira, Rui M. A.; Stegner, Alexandre; Couvelard, Xavier; Araujo, Isabel B.; Testor, Pierre; Lorenzo, Alvaro. |
| Island wakes are areas of a strong eddy activity influencing the availability and transport of organic matter in the ocean which, in turn impact biological productivity. Despite this, eddy formation in the lee of North Atlantic tropical islands is scarcely documented, except for the Canary Islands. Moreover, the occurrence of anticyclones leeward of Madeira has seldom been detected. During the summer of 2011, a multiplatform approach, combining satellite data with in situ measurements, was used to study an anticyclonic eddy generated in the lee of the Madeira Island. The main objective was to confirm recent numerical evidence suggesting that orographically perturbed winds can induce anticyclonic eddies leeward of Madeira, particularly during summer months.... |
| Tipo: Text |
Palavras-chave: Boundary-layer; Inertial instability; Mode water; Mixed layer; Intrathermocline eddies; Wake. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00197/30846/29209.pdf |
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| Garreau, Pierre; Dumas, Franck; Louazel, Stephanie; Correard, Stéphanie; Fercocq, Solenn; Le Menn, Marc; Serpette, Alain; Garnier, Valerie; Stegner, Alexandre; Le Vu, Briac; Doglioli, Andrea; Gregori, Gerald. |
| From 2015 to 2018 four field experiments (seven legs) were performed in the Western Mediterranean basin during winter or early spring. The main objectives were the assessment of high-resolution modeling and the observation of mesoscale structure and associated ageostrophic dynamics. Thanks to the intensive use of a towed vehicle undulating in the upper oceanic layer between 0 and 400 m depth (SeaSoar), a large number of very high resolution hydrographic transects (total length about 10 000 km) were measured, observing mesoscale dynamics (slope current and its instabilities, anticyclonic eddies, submesoscale coherent vortices, frontal dynamics, convection events, strait outflows) and submesoscale processes like stirring, mixed-layer or symmetric... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00611/72277/71071.pdf |
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| De Marez, Charly; Carton, Xavier; L'Hegaret, Pierre; Meunier, Thomas; Stegner, Alexandre; Le Vu, Briac; Morvan, Mathieu. |
| Oceanic vortices are ubiquitous in the ocean. They dominate the sub-inertial energy spectrum, and their dynamics is key for the evolution of the water column properties. The merger of two like-signed coherent vortices, which ultimately results in the formation of a larger vortex, provides an efficient mechanism for the lateral mixing of water masses in the ocean. Understanding the conditions of such interaction in the ocean is thus essential. Here, we use a merger detection algorithm to draw a global picture of this process in the ocean. We show that vortex mergers are not isolated, contrary to the hypothesis made in most earlier studies. Paradoxically, the merging distance is well reproduced by isolated vortex merger numerical simulations, but it is... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00657/76873/78117.pdf |
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