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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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| 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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| De Marez, Charly; Meunier, Thomas; Morvan, Mathieu; L’hégaret, Pierre; Carton, Xavier. |
| We investigate the stability of a composite cyclone representative of Arabian Sea eddies using a high resolution primitive equation model. We observe that the eddy is unstable with respect to a mixed barotropic/baroclinic instability, leading to the growth of an azimuthal mode 2 perturbation. The latter deforms the eddy, which eventually evolves into a tripole after about 4 months of simulation. The presence of a critical level for the most unstable mode generates sharp fronts in the surface mixed layer where the Rossby number is large. These fronts then become unstable, and this generates submesoscale cyclones and filaments. Near these fronts, diapycnal mixing occurs, causing the potential vorticity to change sign locally, and symmetric instability to... |
| Tipo: Text |
Palavras-chave: Mesoscale; Eddy; Instability; Submesoscale; Vortex. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00598/70967/69196.pdf |
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| Morvan, Mathieu; Carton, Xavier; Corréard, Stéphanie; Baraille, Rémy. |
| We have investigated the surface and subsurface submesoscale dynamics in the Gulf of Aden and the Gulf of Oman. Our results are based on the analyses of regional numerical simulations performed with a primitive equation model (HYCOM) at submesoscale permitting horizontal resolution. A model zoom for each gulf was embedded in a regional mesoscale-resolving simulation. In the Gulf of Aden and the Gulf of Oman, the interactions of mesoscale structures and fronts instabilities form submesoscale eddies and filaments. Rotational energy spectra show that the Gulf of Aden has a higher ratio of submesoscale to mesocale energy than the Gulf of Oman. Fast waves (internal gravity waves, tidal waves, Kelvin waves) and slow waves (Rossby waves) were characterized via... |
| Tipo: Text |
Palavras-chave: Submesoscale instabilities; Eddies and waves; Upwelling fronts. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00645/75698/76603.pdf |
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| Morvan, Mathieu; Carton, Xavier. |
| The Omani Coastal Current (OCC) flowing northward along the southern coast of Oman during the summer monsoon is associated with an upwelling system. The mesoscale circulation of the western Arabian Sea is dominated by energetic mesoscale eddies down to about 1000 m depth. They drive the pathways of the upwelling water masses and the Persian Gulf Outflow water. This paper focuses on the sub-mesoscale frontal dynamics in the OCC by analyzing the results from a regional realistic numerical simulation performed with a primitive equation model. Off the Omani coast, the interaction between the upwelling fronts and the mesoscale eddies triggers the frontogenesis at play in the surface mixed layer during the summer monsoon. In spring, sub-mesoscale eddies are... |
| Tipo: Text |
Palavras-chave: Sub-mesoscale; Fronts; Instabilities. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00623/73483/72784.pdf |
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| De Marez, Charly; Carton, Xavier; Morvan, Mathieu; Reinaud, Jean N.. |
| We study the influence of bottom topography on the interaction of two identical vortices in a two-layer, quasi-geostrophic model. The two vortices have piecewise-uniform potential vorticity and are lying in the upper layer of the model. The topography is a smooth bottom slope. For two cyclones, topography modifies the merger critical distance and the merger efficiency: the topographic wave and vortices can advect the two cyclones along the shelf when they are initially far from it or towards the shelf when they are initially closer to it. They can also advect the two cyclones towards each other and thus favour merger. The cyclones deform, and the potential vorticity field undergoes filamentation. Regimes of partial vortex merger or of vortex splitting are... |
| Tipo: Text |
Palavras-chave: Vortex interaction; Topography; Quasi-geostrophic model. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00600/71250/69625.pdf |
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| Morvan, Mathieu; L'Hégaret, Pierre; Carton, Xavier; Gula, Jonathan; Vic, Clement; Sokolovskiy, Mikhail; Koshel, Konstantin. |
| The Persian Gulf Water and Red Sea Water are salty and dense waters recirculating at subsurface in the Gulf of Oman and the Gulf of Aden respectively, under the influence of mesoscale eddies which dominate the surface flow in both semi-enclosed basins. In situ measurements combined with altimetry indicate that the Persian Gulf Water is driven by mesoscale eddies in the form of filaments and submesoscale structures. In this paper, we study the formation and the life cycle of intense submesoscale vortices and their impact on the spread of Persian Gulf Water and Red Sea Water. We use a three-dimensional hydrostatic model with submesoscale-resolving resolution to study the evolution of submesoscale vortices. Our configuration is an idealized version of the... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00589/70153/68140.pdf |
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