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| Registros recuperados: 17 | |
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| L'Hegaret, Pierre; Lacour, Leo; Carton, Xavier; Roullet, Guillaume; Baraille, Remy; Correard, Stephanie. |
| Trajectories and hydrological data from two Argo floats indicate that warm and salty water at 200–300-m depths was ejected from the coast of Oman, near Ras al Hamra, in spring 2008, 2011, and 2012. This warm and salty water, Persian Gulf Water (PGW), once ejected from the coast, recirculated cyclonically in the western Sea of Oman, but also flowed eastward along the Iranian and Pakistani coasts. There, it was expelled seaward by mesoscale eddies as shown by other float data. Seasonal maps of salinity were computed from all available Argo floats; they showed that, in spring, PGW is present in the middle and north of the Sea of Oman, contrary to fall, when the salinity maxima lie southeast of Ras al Hadd. The ejection of PGW from Ras al Hamra is related here... |
| Tipo: Text |
Palavras-chave: Sea of Oman; Outflow; Eddies; Argo floats. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00171/28206/33894.pdf |
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| Roullet, Guillaume; Klein, Patrice. |
| Review of three studies devoted to the available potential energy (APE) leads to the proposal of a diagnosis for APE, well-suited for rotating stratified flows within the primitive equations (PE) framework in which anharmonic effects (due to large vertical displacements of isopycnals) are permitted. The chosen diagnosis is based on the APE definition of Holliday & McIntyre (J. Fluid Mech., vol. 107, 1981, pp. 221-225) and uses the background stratification of Winters et al. (J. Fluid Mech., vol. 289, 1995, pp. 115-128). Subsequent evaluation of the APE in a PE direct simulation (1/100 degrees, 200 levels) of oceanic mesoscale turbulence indicates that anharmonic effects are significant. These effects are due to large vertical displacements of the... |
| Tipo: Text |
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| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-6391.pdf |
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| Roullet, Guillaume; Molemaker, Maarten Jeroen; Ducousso, Nicolas; Dubos, Thomas. |
| In anticipation of relaxing the hydrostatic assumption in a sigma coordinates primitive equations ocean model, we show how a projection method can be designed with the use of a compact symmetric 15-point stencil for the Poisson equation. This is achieved by recognizing that, owing the non-orthogonality of the grid, the velocity has a contravariant and covariant set of components. The two sets play a different role in the primitive equations: the contravariant components enter the definition of the model fluxes, whereas the covariant components experience the forces and in particular the pressure gradient. By treating these two sets separately, the discretized gradient and divergence operators are simple finite differences. The two sets of components are... |
| Tipo: Text |
Palavras-chave: Non-hydrostatic; Sigma coordinates; Poisson equation. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00399/51045/51818.pdf |
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| Roullet, Guillaume; Klein, Patrice. |
| We address the problem of cyclone-anticyclone asymmetry in geophysical turbulence using a direct numerical simulation with high Reynolds number Re similar to 15 000 that includes an active upper boundary and interior dynamics. The regime, characterized by a finite Rossby number (Ro similar to 0.6) strongly departs from the classical quasigeostrophic regime. The numerical resolution is pushed to the limit of today's supercomputer capabilities ensuring more than two decades free of viscous effects. The results show a strong cyclonic dominance in the upper layers that is stronger for filaments than for vortices. This is in contrast with similar studies that have no active upper boundary which reported either anticyclone dominance or a symmetry between... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00005/11587/8240.pdf |
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| Lahaye, Noe; Gula, Jonathan; Thurnherr, Andreas M.; Reverdin, Gilles; Bouruet-aubertot, Pascale; Roullet, Guillaume. |
| Over mid-ocean ridges, the interaction between the currents and the topography gives rise to complex flows, which drive the transport properties of biogeochemical constituents, and especially those associated with hydrothermal vents, thus impacting associated ecosystems. This paper describes the circulation in the rift valley along the Azores sector of the North Mid-Atlantic Ridge, using a combination of in-situ data from several surveys and realistic high-resolution modeling. It confirms the presence of a mean deep current with an up-valley branch intensified along the right inner flank of the valley (looking downstream), and a weaker down-valley branch flowing at shallower depth along the opposite flank. The hydrographic properties of the rift-valley... |
| Tipo: Text |
Palavras-chave: Deep currents; Transport; Deep turbulence; Internal waves and tides; Realistic modeling; In situ observation. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00584/69630/67486.pdf |
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| Jouanno, Julien; Capet, Xavier; Madec, Gurvan; Roullet, Guillaume; Klein, Patrice. |
| The aim of this study is to clarify the role of the Southern Ocean storms on interior mixing and meridional overturning circulation. A periodic and idealized numerical model has been designed to represent the key physical processes of a zonal portion of the Southern Ocean located between 70 and 40° S. It incorporates physical ingredients deemed essential for Southern Ocean functioning: rough topography, seasonally varying air–sea fluxes, and high-latitude storms with analytical form. The forcing strategy ensures that the time mean wind stress is the same between the different simulations, so the effect of the storms on the mean wind stress and resulting impacts on the Southern Ocean dynamics are not considered in this study. Level and distribution of... |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00343/45404/44919.pdf |
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| Vic, C.; Roullet, Guillaume; Capet, Xavier; Carton, Xavier; Molemaker, Maarten Jeroen; Gula, J.. |
| The Persian Gulf feeds a warm and salty outflow in the Gulf of Oman (northern Arabian Sea). The salt climatological distribution is relatively smooth in the Gulf of Oman, and the signature of a slope current carrying salty waters is difficult to distinguish hundreds of kilometers past the Strait of Hormuz, in contrast to other outflows of the world ocean. This study focuses on the mechanisms involved in the spreading of Persian Gulf Water (PGW) in the Gulf of Oman, using a regional primitive equation numerical simulation. The authors show that the dispersion of PGW occurs through a regime that is distinct from, for example, the one responsible for the Mediterranean outflow dispersion. The background mesoscale eddy field is energetic and participates... |
| Tipo: Text |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00302/41332/40512.pdf |
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| Cannat, Mathilde; Sarradin, Pierre-marie; Blandin, Jerome; Ballu, Valérie; Barreyre, Thibaut; Chavagnac, Valérie; Colaco, Ana; Crawford, Wayne; Daniel, Romuald; Escartin, Javier; Legrand, Julien; Matabos, Marjolaine; Rommevaux, Céline; Roullet, Guillaume; Reverdin, Gilles; Sarrazin, Jozee. |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00353/46444/46194.pdf |
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| Roullet, Guillaume; Capet, Xavier; Maze, Guillaume. |
| By combining all Argo profiles for the period 2002 to present, a cumulative density function is constructed on a 3D grid of the global ocean. This function quantifies the statistics of isopycnals: time-averaged density, root- mean square (rms) of isopycnal displacement, and Eddy Available Potential Energy (EAPE). EAPE is the analogue of the eddy kinetic energy, but for the potential energy reservoir. Because it is essentially tied to the spatial struc- ture and magnitude of mesoscale activity, EAPE is an important quantity that should be useful to evaluate eddy resolving/permitting model turbu- lence and circulation. Among other striking features are the turbulent be- havior of Pacific and southern Atlantic Tsuchiya jets and subsurface EAPE maxima in some... |
| Tipo: Text |
Palavras-chave: Argo floats; Eddy available potential energy; Interior turbulence. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00175/28579/26966.pdf |
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| Capet, Xavier; Roullet, Guillaume; Klein, Patrice; Maze, Guillaume. |
| This study focuses on the description of an oceanic variant of the Charney baroclinic instability, arising from the joint presence of i) an equatorward buoyancy gradient that extends from the surface into the ocean interior and ii) reduced subsurface stratification, e.g., as produced by wintertime convection or subduction. We analyze forced-dissipative simulations with and without Charney baroclinic instability (C-BCI). In the former C-BCI strengthens near-surface frontal activity with important consequences in terms of turbulent statistics: increased variance of vertical vorticity and velocity, increased vertical turbulent fluxes. Energetic consequences are explored. Despite the atypical enhancement of submesoscale activity in the simulation subjected to... |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00347/45785/45429.pdf |
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| Lahaye, Noe; Gula, Jonathan; Roullet, Guillaume. |
| Internal tides are a predominant source of high‐frequency variability and diapycnal mixing in the ocean. Understanding their dynamics and lifecycle is necessary to better understand their role in the ocean circulation. In this paper, we describe and quantify internal tide generation, propagation and dissipation in a sector of the North Mid‐Atlantic Ridge, using high‐resolution numerical simulations with realistic bathymetry and stratification. We show that the generation and dissipation of internal tides, as well as the distribution of internal tides amongst vertical modes, exhibit high spatial variability. We find that topographic scattering leads to a significant transfer of energy towards high vertical modes and thereby enhances internal tide... |
| Tipo: Text |
Palavras-chave: Energy dissipation & Mixing; Internal tides; Internal waves; Topographic scattering. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00658/77003/78259.pdf |
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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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| Vic, Clement; Roullet, Guillaume; Carton, Xavier; Capet, X.. |
| The Great Whirl (GW) is a persistent anticyclonic mesoscale eddy that is observed seasonally in the Arabian Sea during a period embedding the 3 months of the southwest monsoon (June–July–August) at a quasi-steady location. Its dynamics remain unclear despite it being one of the largest coherent vortices in the world ocean. Realistic regional numerical experiments using ROMS are performed to investigate the life cycle of the GW, which is not well resolved by sparse available in situ measurements in the region. Using a set of sensitivity experiments and an accurate temporal characterization of the eddy properties (including position, radius, depth, and vorticity) we (i) confirm the role of basin-scale downwelling Rossby waves in the GW generation, (ii)... |
| Tipo: Text |
Palavras-chave: Arabian Sea; Indian Ocean; Great Whirl; Mesoscale dynamics; ROMS; Rossby waves. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00211/32197/30631.pdf |
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| Lahaye, Noe; Gula, Jonathan; Roullet, Guillaume. |
| The upper ocean is energetic at scales below the Rossby deformation radius owing to the existence of internal waves and submesoscale fronts and vortices. These contribute significantly to energy dissipation, tracer mixing and exchanges between the ocean surface layer, the ocean interior, and the atmospheric boundary layer. Internal waves and submesoscale motions both undergo strong spatial and seasonal variations, driven by different mechanisms. Here, we investigate the sea surface signature of internal waves and its seasonality using linear wave theory and a high‐resolution realistic simulation. In summer, internal waves are greatly amplified near the surface mostly due to a thin mixed layer bounded by a seasonal pycnocline. This surface amplification is... |
| Tipo: Text |
Palavras-chave: Internal tide; Submesosacle dynamics; Seasonality. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00486/59746/62847.pdf |
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| Vic, Clement; Capet, Xavier; Roullet, Guillaume; Carton, Xavier; ,. |
| Despite its climatic and ecosystemic significance, the coastal upwelling that takes place off Oman is not well understood. A primitive-equation, regional model forced by climatological wind stress is used to investigate its dynamics and to compare it with the better-known Eastern Boundary Upwellings (EBUs). The solution compares favorably with existing observations, simulating well the seasonal cycles of thermal structure, surface circulation (mean and turbulent), and sea-surface temperature (SST). There is a 1.5-month lag between the maximum of the upwelling-favorable wind-stress-curl forcing and the oceanic response (minima in sea-surface height and SST), which we attribute to onshore-propagating Rossby waves. A southwestward-flowing undercurrent... |
| Tipo: Text |
Palavras-chave: Oman; Upwelling; Arabian sea; ROMS; Rossby waves; Eddy kinetic energy. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00382/49350/49752.pdf |
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| Registros recuperados: 17 | |
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