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| Registros recuperados: 15 | |
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| Barbosa Aguiar, A. C.; Menesguen, Claire; Le Gentil, Sylvie; Schopp, Richard; Carton, Xavier. |
| Nearly all the subsurface eddies detected in seismic imaging of sections in the northeast Atlantic have been assumed to be anticyclones containing Mediterranean Water (MW). Fewer MW cyclones have been observed and studied. In this study, the work of previous numerical studies is extended to investigate some characteristics of layering surrounding MW cyclones, using a primitive equation model with equal diffusivities for salinity and temperature to suppress the effects of double diffusion. It is shown that, after a stable state is reached, both anticyclones and cyclones display similar patterns of layering: stacked thin layers of high acoustic reflectivity located above and below the core of each vortex, which do not match isopycnals. The authors conclude... |
| Tipo: Text |
Palavras-chave: Geographic location/entity; North Atlantic Ocean; Circulation/ Dynamics; Small scale processes; Atm/Ocean Structure/ Phenomena; Eddies; Vortices; Observational techniques and algorithms; Acoustic measurements/effects; Models and modeling; Primitive equations model. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00281/39190/37746.pdf |
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| Menesguen, Claire; Le Gentil, Sylvie; Marchesiello, P.; Ducousso, N.. |
| The increase of computational capabilities led recent studies to implement very high resolution simulations that gave access to new scale interaction processes, particularly those associated with the transfer of energy from the oceanic mesoscales to smaller scales through an interior route to dissipation which is still under-explored. In this context, we study spin down simulations of a mesoscale interior vortex, unstable to a mixed baroclinic-barotropic instability. Even though the global energy is almost conserved, some energy is transferred down to dissipation scales during the development of instabilities. However, in our parameter regime, there is no substantial forward energy cascade sustained by unbalanced dynamics. Rather than exploring the... |
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| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00435/54690/56128.pdf |
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| Klein, Patrice; Isern-fontanet, Jordi; Lapeyre, Guillaume; Roullet, G.; Danioux, Eric; Chapron, Bertrand; Le Gentil, Sylvie; Sasaki, H.. |
| A surface Quasi-Geostrophy based (eSQG) method to diagnose the vertical velocity field from Sea Surface Height (SSH) is assessed using high resolution simulations. These simulations concern a turbulent eddy field with large Rossby numbers and energetic wind-driven motions. Results indicate that low-frequency vertical velocities (and also horizontal motions) can be reconstructed within a range of scales between 20 km and 400 km from the surface down to 500 m. The only information needed is a single high-resolution SSH snapshot and information on the large-scale vertical stratification. Inertial motions are naturally filtered because they do not contaminate SSH as we demonstrate. These results are encouraging and further strengthen previous studies using the... |
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| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00000/11094/7418.pdf |
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| Hua, Bach-lien; Le Gentil, Sylvie; Orlandi, P. |
| The first flow regimes which have been observed experimentally for a circular Couette flow with a stable, axial stratification in density are investigated through direct numerical simulations of the three-dimensional Navier-Stokes equations for a Boussinesq fluid. The setup of two concentric cylinders has a nondimensional gap width of epsilon=(b-a)/a=0.289; the outer cylinder is tired and the stratification in density in the axial direction is linear. The main effect of an axial density stratification is to reduce the height of the Taylor vortices and to cause the formation of density layers of small aspect ratio. For large enough Prandtl number, the primary bifurcation from circular Couette flow is found to be axisymmetric and of Hopf-type in the direct... |
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| Ano: 1997 |
URL: http://archimer.ifremer.fr/doc/00336/44750/57508.pdf |
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| Klein, Patrice; Hua, Bach-lien; Le Gentil, Sylvie; Sasaki, Hideharu. |
| The big challenge of the next decade for the oceanic sciences is to adopt a multi-scale approach because of the strong nonlinearity of the oceanic fluid. This can be undertaken only through numerical simulations with ultra-high resolution. Within this context, the purpose of our projects is to fully explore two energetic dynamical oceanic regimes that have a major impact on the general oceanic circulation: the mesoscale eddy regime at mid-latitudes and the equatorial regime. Expected results will help for the configuration of realistic numerical simulations to be performed in 2006 by the OFES group on the Earth Simulator and they should benefit to future climate models. These studies make use of the Primitive Equations model ROMS (Regional Ocean Modelling... |
| Tipo: Text |
Palavras-chave: Mesoscale oceanic eddies; Equatorial dynamics. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/00067/17783/15306.pdf |
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| Klein, Patrice; Hua, Bach-lien; Le Gentil, Sylvie; Fruman, Mark; Menesguen, Claire; Sasaki, Hideharu. |
| The big challenge of the next decade for the oceanic sciences is to adopt a multi-scale approach because of the strong nonlinearity of the oceanic fluid. This can be undertaken only through numerical simulations with ultra-high resolution. Within this context, the purpose of our project is to fully explore two energetic dynamical oceanic regimes that have a major impact on the general oceanic circulation: the mesoscale eddy regime at mid-latitudes and the equatorial regime. Results will help for the configuration of realistic numerical simulations to be performed in 2007-2008 by the OFES group on the Earth Simulator and also should benefit to future climate models. These studies make use of the Primitive Equations model ROMS (Regional Ocean Modelling... |
| Tipo: Text |
Palavras-chave: Mesoscale oceanic eddies; Equatorial dynamics. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/00067/17784/15307.pdf |
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| Hua, Bach-lien; Menesguen, Claire; Le Gentil, Sylvie; Schopp, Richard; Marsset, Bruno; Aiki, Hidenori. |
| Evidence of persistent layering, with a vertical stacking of sharp variations in temperature, has been presented recently at the vertical and lateral periphery of energetic oceanic vortices through seismic imaging of the water column. The stacking has vertical scales ranging from a few metres up to 100 m and a lateral spatial coherence of several tens of kilometres comparable with the vortex horizontal size. Inside this layering, in situ data display a [k(h)(-5/3)k(h)(2)] scaling law of horizontal scales for two different quantities, temperature and a proxy for its vertical derivative, but for two different ranges of wavelengths, between 5 and 50 km for temperature and between 500 m and 5 km for its vertical gradient. In this study, we explore the dynamics... |
| Tipo: Text |
Palavras-chave: Geostrophic turbulence; Quasi; Geostrophic flows; Stratified flows. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00159/27070/25322.pdf |
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| Dunphy, Michael; Ponte, Aurelien; Klein, Patrice; Le Gentil, Sylvie. |
| Understanding how internal tides distort and lose coherence as they propagate through the ocean has been identified as a key issue for interpreting data from the upcoming wide-swath altimeter mission SWOT. This study addresses that issue through the analysis of numerical experiments where a low mode internal tide propagates through a quasi-geostrophic turbulent jet. We present a set of reduced equations based on vertical mode projections that describe the dynamics of the low-mode internal tides as they propagate through the slower turbulent field. Diagnostics of the terms responsible for the interaction between the wave and the slow circulation are computed from the numerical outputs. The large scale change of stratification, on top of eddies and jet... |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00342/45364/44853.pdf |
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| Ponte, Aurelien; Klein, Patrice; Dunphy, Michael; Le Gentil, Sylvie. |
| The performance of a tentative method that disentangles the contributions of a low-mode internal tide on sea level from that of the balanced mesoscale eddies is examined using an idealized high resolution numerical simulation. This disentanglement is essential for proper estimation from sea level of the ocean circulation related to balanced motions. The method relies on an independent observation of the sea surface water density whose variations are 1/dominated by the balanced dynamics and 2/correlate with variations of potential vorticity at depth for the chosen regime of surface-intensified turbulence. The surface density therefore leads via potential vorticity inversion to an estimate of the balanced contribution to sea level fluctuations. The... |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00374/48487/48761.pdf |
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| Klein, Patrice; Lapeyre, Guillaume; Siegelman, Lia; Qiu, Bo; Fu, Lee‐lueng; Torres, Hector; Su, Zhan; Menemenlis, Dimitris; Le Gentil, Sylvie. |
| Satellite observations of the last two decades have led to a major breakthrough emphasizing the existence of a strongly energetic mesoscale turbulent eddy field in all the oceans. This ocean mesoscale turbulence (OMT) is characterized by cyclonic and anticyclonic eddies (with a 100‐‐300 km size and depth scales of ~500‐‐1000 m) that capture approximatively 80% of the total kinetic energy and is now known to significantly impact the large‐scale ocean circulation, the ocean's carbon storage, the air‐sea interactions and therefore the Earth climate as a whole. However, OMT revealed by satellite observations has properties that differ from those related to classical geostrophic turbulence theories. In the last decade, a large number of theoretical and... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00488/59951/63202.pdf |
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| Klein, Patrice; Hua, Bach-lien; Le Gentil, Sylvie; Sasaki, Hideharu. |
| The purpose of this project is to study the dynamics of the upper oceanic layers (the first 1000m below the surface) and principally to get new insights on the effectiveness of the oceanic vertical pump at a basin scale through numerical experiments using ultra-high resolution. If the magnitude of this vertical pump when using such a resolution is much larger than anticipated, then the expected results should have an important impact on basin-scale SST and circulation through the vertical fluxes of heat and potential vorticity. Indeed preliminary studies already indicate the significant contribution of this eddy vertical pump to the modification of the surface layers heat content ([1], [2]). Thus the expected new results should be of importance for climate... |
| Tipo: Text |
Palavras-chave: Mesoscale oceanic eddies; Submesoscale dynamics; Vertical pump. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/00067/17782/15304.pdf |
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| Registros recuperados: 15 | |
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