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Registros recuperados: 35 | |
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Lique, Camille. |
While perhaps the most obvious, ice retreat is just one aspect of a changing Arctic system. The Arctic Ocean is also undergoing unprecedented modifications, that mostly affect its heat and freshwater budgets. As the signal of Arctic change is expected to have its major climatic impact by reaching south the subarctic seas, on either side of Greenland, to modulate the Atlantic thermohaline circulation, the objective of this thesis is to investigate the variability of the exports of volume, heat, freshwater and sea-ice from the Arctic Ocean to the North Atlantic. First, a realistic simulation from 1958 to 2002 run with a global ocean/sea-ice model is used to investigate some aspects of the variability of the Arctic freshwater budget, trying to understand... |
Tipo: Text |
Palavras-chave: Océan Arctique; Bilan d'eau douce; Flux d'eau douce; Glace de mer; Modèle numérique - Analyse Lagrangienne - Forçages atmosphériques; Arctic Ocean; Freshwater budget; Freshwater flux; Sea ice; Numerical model; Lagrangian analysis; Atmospheric forcing. |
Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00015/12597/9474.pdf |
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Treguier, Anne-marie; Boebel, O; Barnier, B; Madec, G. |
A 1/6degrees resolution primitive equation model of the Atlantic circulation is analyzed in the Agulhas region. The model has a realistic level of eddy kinetic energy, and produces anticyclonic Agulhas rings as well as cyclonic structures. In the model as well as in the data, ring trajectories undergo a transition between a turbulent character in the Cape Basin and a steady propagation in the rest of the South Atlantic. The topography of the Walvis Ridge does not seem to play a part in generating this contrast in the model. The model shows that cyclones are primarily generated from the negative shear vorticity side of the Agulhas Current as it leaves the coast, and they are most of the time paired with anticyclones in dipolar or tripolar structures.... |
Tipo: Text |
Palavras-chave: South Africa; South Atlantic Ocean; Numerical model; Ocean currents; Oceanic eddies; Eddy flux. |
Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/2003/publication-453.pdf |
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Carton, Xavier; Ciani, Daniele; Verron, J.; Reinaud, J.; Sokolovskiy, M.. |
The merger of two identical surface temperature vortices is studied in the surface quasi-geostrophic model. The motivation for this study is the observation of the merger of submesoscale vortices in the ocean. Firstly, the interaction between two point vortices, in the absence or in the presence of an external deformation field, is investigated. The rotation rate of the vortices, their stationary positions and the stability of these positions are determined. Then, a numerical model provides the steady states of two finite-area, constant-temperature, vortices. Such states are less deformed than their counterparts in two-dimensional incompressible flows. Finally, numerical simulations of the nonlinear surface quasi-geostrophic equations are used to... |
Tipo: Text |
Palavras-chave: Shear/strain flow; Steady states; Vortex merger; Numerical model; Surface quasi-geostrophy; Critical distance. |
Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00323/43460/42864.pdf |
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Morvan, Barthelemy; Bles, G; Dumergue, Nicolas; Priour, Daniel. |
The evaluation of the mesh opening stiffness of fishing nets is an important issue in assessing the selectivity of trawls. It appeared that a larger bending rigidity of twines decreases the mesh opening and could reduce the escapement of fish. Nevertheless, netting structure is complex. A netting is made up of braided twines made of polyethylene or polyamide. These twines are tied with non-symmetrical knots. Thus, these assemblies develop contact-friction interactions. Moreover, the netting can be subject to large deformation. In this study, we investigate the responses of netting samples to different types of solicitations. Samples are loaded and unloaded with creep and relaxation stages, with different boundary conditions. Then, two models have been... |
Tipo: Text |
Palavras-chave: Numerical model; Experiments; Braided twine; Mesh opening rigidity; Large deformation.. |
Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00348/45899/45581.pdf |
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Ganachaud, Alexandre; Mercier, Herle. |
[1] Wind friction at the ocean surface introduces energetic variations in the net mass transport across the oceanic basins. To conserve mass, the whole water column adjusts rapidly, introducing a depth-independent perturbation in the pressure field. This signal is analyzed in a high resolution numerical model of the Atlantic Ocean. While the pressure perturbation cannot be extracted from the energetic sea surface height signals, it represents up to 90% of the bottom pressure signal when integrated across the Atlantic Ocean in the daily and monthly frequencies. This signal will be an important part of the signal measured by the GRACE (Gravity Recovery And Climate Experiment) mission. |
Tipo: Text |
Palavras-chave: Eckman transport; Numerical model; Pressure perturbation; Ocean surface. |
Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/2002/publication-490.pdf |
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Louazel, Stephanie; Hua, Bach-lien. |
The purpose of this paper is to study the erosion of eddies by filamentation in a shallow-water model where both fast and slow components of the dynamics coexist. In presence of inertia-gravity waves this filamentation process is indeed found to be altered. However, the information required to analyze the filamentation process is shown to be entirely captured by the slow component of the flow and regions of filament ejection can be identified from a diagnostic criterion based on instantaneous slow quantities. This is illustrated numerically in a reduced gravity model for an initial elliptic vortex of distributed potential vorticity in presence of Poincare waves. (C) 2004 American Institute of Physics. |
Tipo: Text |
Palavras-chave: Numerical model; Filamentation; Vorticity; Eddies. |
Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-711.pdf |
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Morvan, Barthelemy; Priour, Daniel; Guede, Zakoua; Bles, G.. |
The evaluation of the mesh resistance to opening of fishing nets is an important issue in assessing the selectivity of trawls by numerical methods. Sala et al. (2007) proposed a method using a relatively expensive experimental device ensuring the 2D deformation of net sample. De la Prada and Gonzales (2015) proposed a simple uni-axial experimental set-up, which stretches a sample in the transverse direction of the meshes while leaving free its deformation in the normal direction. Both authors (Sala and De la Prada) assumed that the deformation is uniform in the sample. The present study aims at developing a finite element model taking into account the mesh resistance to opening of nets, allowing the simulation of non-uniform deformation. Mechanical... |
Tipo: Text |
Palavras-chave: Netting; Mesh resistance to opening; Bending stiffness; Experiment; Numerical model. |
Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00347/45813/49043.pdf |
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Pous, Stephane; Lazure, Pascal; Carton, Xavier. |
Previous studies modeling the circulation and thermohaline structure in the Persian Gulf have suggested that interannual variability and vertical mixing processes could explain the model biases when compared to the few observations available. Here, a realistic, interannual, high-resolution model of the Persian Gulf is presented, validated against observations and then used to describe the intraseasonal to interannual variability in the circulation, water mass formation and exchange through the Strait of Hormuz. Sensitivity experiments to model settings, in particular vertical mixing parameterizations, have been performed in order to have the best comparison with all available observations. Main circulation and water mass characteristics correspond well to... |
Tipo: Text |
Palavras-chave: Persian Gulf; Strait of Hormuz; Numerical model; Hydrology; Currents; Interannual variability. |
Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00244/35563/35324.pdf |
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Dubarbier, Benjamin; Castelle, Bruno; Marieu, Vincent; Michallet, Hervé; Grasso, Florent; Ruessink, Gerben. |
The recent advances of numerical beach profile models allowed the simulation of on/offshore sandbar migrations on timescales of weeks to months with fair success. These models were systematically applied to natural, persistently evolving, beaches. In this contribution, we apply our model to small-scale laboratory experiments for which coarse and lightweight sediment is used to satisfy the laws of similitude in the flume. Such experiments can result in equilibrium beach profiles and provide detailed information on the respective role of undertow and wave nonlinearities on sediment transport and the resulting cross-shore sandbar migration. Here we first apply the coupled, wave-averaged, cross-shore waves-currents-bathymetric evolution model 1DBeach to an... |
Tipo: Text |
Palavras-chave: Beach profile; Numerical model; Physical modelling; Equilibrium profile; Sandbar migration. |
Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00180/29089/27503.pdf |
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Cai, Sq; Huang, Qz; Long, Xm. |
A three-dimensional baroclinic shelf sea model is employed to simulate the tidal and non-tidal residual current in the South China Sea. The four most significant constituents, M-2, S-2, K-1 and O-1, are included in the experiments with tidal effect. At most stations, the computed harmonic constants agree well with the observed ones. The circulations of the South China Sea in summer (August) and winter (December) are mainly discussed. It is shown that the barotropic tidal residual current is too weak to affect the South China Sea circulation, whilst the contribution of the baroclinic tidal residual current to the South China Sea circulation would be important in the continental shelf sea areas, especially in the Gulf of Thailand and Gulf of Tonkin. In the... |
Tipo: Text |
Palavras-chave: Marée; Courant résiduel; Modèle numérique; Mer de Chine du Sud; Tides; Tidal current; Residual current; Numerical model; South China Sea. |
Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/00321/43251/42982.pdf |
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De La Prada, Amelia; Priour, Daniel. |
Thirty-seven hauls of a bottom trawl were carried out, as part of a national French project. These sea trials were undertaken in an area with strong currents: up to 1 knot. The measurements at sea of the bottom bridle’s tension show a clear effect of the current. Although the water speed relative to the trawl is constant, when the boat tows with current, the bottom bridle’s tension increases, and when the boat tows against the current, the bottom bridle’s tension decreases. The mean bottom bridle tension is 7840 N and increases with a slope of 1197 N for each m/s of current. The current has almost no effect on the top bridle’s tension: for a mean value of approximately 9810 N, the increment is 106 N for each m/s of current. The modelling of the trawl gear... |
Tipo: Text |
Palavras-chave: Trawl; Data; Numerical model; Bridle tension; Bottom boundary layer; Water speed. |
Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00266/37710/35800.pdf |
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Harnois, V.; Weller, Sam D.; Johanning, L.; Thies, P. R.; Le Boulluec, Marc; Le Roux, Dominique; Soule, Veronique; Ohana, Jeremy. |
The design of wave energy mooring systems is challenging: overdesign incurs a significant cost penalty, underdesign may lead to a premature failure and incorrect design could reduce the power production. Consequently, compliant mooring systems are being developed for wave energy applications. This paper presents tank test results for a scale model of the buoy and mooring used at the SouthWest Mooring Test Facility (SWMTF), an offshore facility developed to conduct long-term sea trials for wave energy device moorings. A compliant three leg catenary mooring system using Nylon ropes in the water column is investigated. Preliminary static, quasi-static, decay, regular and irregular wave tests were conducted on the 1:5 scale model, using the Ifremer basin in... |
Tipo: Text |
Palavras-chave: Wave energy converter; Tank tests; Numerical model; Highly dynamic mooring system; Fibre rope. |
Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00233/34375/35785.pdf |
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Treguier, Anne-marie; Chassignet, Eric P.; Le Boyer, Arnaud; Pinardi, Nadia. |
We present a historical perspective on ocean mesoscale variability and turbulence, from the physical basis and the first numerical models to recent simulations and forecasts. In the mesoscale range (typically, spatial scales of 100 km and time scales of a month), nonlinearity, and energy cascades were well understood in the 1970s, but the emergence of coherent vortices took place much later. New challenges have arisen with the exploration of the submesoscale regime, where frontal dynamics play a key role and the range of flow instabilities is wider than in the quasi-geostrophic regime. Special focus is placed on the interaction of mesoscale turbulence with the continental slopes. The contrast between the variability on the western and eastern boundaries of... |
Tipo: Text |
Palavras-chave: Numerical model; Ocean forecast; Ocean mesoscale turbulence. |
Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00410/52106/52939.pdf |
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Veitch, Jennifer; Hermes, Juliet; Lamont, Tarron; Penven, Pierrick; Dufois, Francois. |
The dynamics and seasonal variability of jet currents on the southern Benguela shelf-edge are investigated using a climatologically forced ROMS model. The jet is primarily forced by the intense horizontal gradients that exist across the southern Benguela shelf. These gradients are set up by nearshore cooling via the strongly seasonal upwelling regime and variable offshore warming by the advection of Agulhas waters. While the nearshore cooling is prevalent only during the spring and summer upwelling season, the offshore warming exists throughout the year. As a result intensified geostrophically adjusted currents exist throughout the year, particularly off the Cape Peninsula and Cape Columbine. However, the distinct shelf-edge jet features are most intense... |
Tipo: Text |
Palavras-chave: Southern Benguela; Shelf-edge jet; Numerical model. |
Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00403/51401/51976.pdf |
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Registros recuperados: 35 | |
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