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Registros recuperados: 11
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A numerical study of tropical cyclone-induced sediment dynamics on the Australian North West Shelf ArchiMer
Dufois, Francois; Lowe, Ryan J.; Rayson, Matthew D.; Branson, Paul M..
Owing to their strong forcing of the ocean surface, tropical cyclones strongly modify the hydrodynamics of Australia's North West Shelf (one of the world's tropical cyclone hotspots), which in turn plays a dominant role in its sediment dynamics. Previous modeling studies have focused on describing the short term sediment dynamics during individual tropical cyclones, but have lacked validation of the responses using field observations. As a consequence, the long term cumulative impact of the tropical cyclones on the residual sediment transport pathways at the shelf scale remains unclear. In this study we apply a sediment transport model over the North West Shelf, validate its performance using an extensive field dataset, and implement a 14 year‐long model...
Tipo: Text Palavras-chave: ROMS; COAWST; Sediment transport model; Tropical cyclone; Surface waves; Sediment pathways.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00449/56078/57601.pdf
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An operational model to simulate post-accidental radionuclide transfers in Toulon marine area: preliminary development ArchiMer
Duffa, Celine; Dufois, Francois; Coudray, Sylvain.
As part of its development of post-accident management tools, the French Institute for Radiological Protection and Nuclear Safety is setting up a model to simulate radionuclide dispersion in the Toulon marine area (one of France's main military ports). The model is based on the MARS 3D code developed by IFREMER. It reproduces hydro-sedimentation phenomena in the Bay of Toulon with a horizontal spatial resolution of 100 m and 30 vertical sigma levels and also factors in radioactive decay and dissolved/particulate distribution of the radionuclides studied. With no tide, the major currents in this area are generated by the wind. The model effectively reproduces the resulting hydrodynamic phenomena, which were measured throughout the summer of 2009 in the...
Tipo: Text Palavras-chave: Bay of Toulon; Radionuclides; Dispersion; MARS.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00053/16465/15998.pdf
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Contraintes de fond dans le Golfe du Lion générées par les houles et les courants ArchiMer
Dufois, Francois; Garreau, Pierre; Le Hir, Pierre.
Simulated data of both currents and waves for the entire year 2001 are used in order to assess their statistical contribution to the erodability power over the shelf of the Gulf of Lion. Bottom circulation patterns are also analysed in response to wind forcing. A method to compute the skin friction component of the total bottom shear stress is then proposed and compared with a classical method.
Tipo: Text Palavras-chave: MARS 3D; Golfe du Lion; Contraintes de peau; Contraintes de fond; Courants; Houles.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-6306.pdf
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Formulating Fine to Medium Sand Erosion for Suspended Sediment Transport Models ArchiMer
Dufois, Francois; Le Hir, Pierre.
The capacity of an advection/diffusion model to predict sand transport under varying wave and current conditions is evaluated. The horizontal sand transport rate is computed by vertical integration of the suspended sediment flux. A correction procedure for the near-bed concentration is proposed so that model results are independent of the vertical resolution. The method can thus be implemented in regional models with operational applications. Simulating equilibrium sand transport rates, when erosion and deposition are balanced, requires a new empirical erosion law that involves the non-dimensional excess shear stress and a parameter that depends on the size of the sand grain. Comparison with several datasets and sediment transport formulae demonstrated the...
Tipo: Text Palavras-chave: Sand; 1DV model; Erosion rate; Suspended sediment transport.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00276/38763/37304.pdf
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Impact of eddies on surface chlorophyll in the South Indian Ocean ArchiMer
Dufois, Francois; Hardman-mountford, Nick J.; Greenwood, Jim; Richardson, Anthony J.; Feng, Ming; Herbette, Steven; Matear, Richard.
A unique feature of the subtropical South Indian Ocean is the existence of anticyclonic eddies that have higher chlorophyll concentrations than cyclonic eddies. Off Western Australia, this anomalous behavior is related to the seeding of anticyclonic eddies with shelf water enriched in phytoplankton biomass and nutrients. Further off-shore, two mechanisms have been suggested to explain the eddy/chlorophyll relationship: (i) eddies originating from the Australian coast maintain their chlorophyll anomaly while propagating westward; and (ii) eddy-induced Ekman upwelling (downwelling) enhances (dampens) nutrient supply in anticyclonic (cyclonic) eddies. Here we describe the relationship between eddies and surface chlorophyll within the South Indian Ocean, and...
Tipo: Text Palavras-chave: Eddies; Chlorophyll; Self-organizing map; Convective mixing; Eddy-induced Ekman pumping.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00233/34464/32862.pdf
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Impact of winter storms on sediment erosion in the Rhone River prodelta and fate of sediment in the Gulf of Lions (North Western Mediterranean Sea) ArchiMer
Dufois, Francois; Verney, Romaric; Le Hir, Pierre; Dumas, Franck; Charmasson, Sabine.
In this study a three-dimensional sediment transport model was developed. The model accounts for both current and wave forcing on the sediment and was implemented over the Gulf of Lions. A two-way nesting technique was used to focus on the Rhone River prodelta which is considered as a sink for riverine sediment. In addition, to understand the resuspension of trapped sediment over the Rhone prodelta, an in situ experiment, called SCOPE, was conducted during the winter 2007/2008. The experiment consisted of measuring hydro-sedimentary parameters using a mooring station comprising a current profiler (ADCP) and an altimeter (acoustic transducer) located in the eastern part of the Rhone prodelta. The three-dimensional transport model was validated using these...
Tipo: Text Palavras-chave: Sediment transport; Gulf of Lions; Rhone prodelta; 3D modelling; ADCP; ALTUS.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00165/27584/25743.pdf
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In situ record of sedimentary processes near the Rhone River mouth during winter events (Gulf of Lions, Mediterranean Sea) ArchiMer
Marion, C.; Dufois, Francois; Arnaud, Mireille; Vella, C..
The environment is impacted by natural and anthropogenic disturbances that occur at different spatial and temporal scales, and that lead to major changes and even disequilibria when exceeding the resiliency capacities of the ecosystem. With an annual mean flow of 1700 m(3) s(-1), the Rhone River is the largest of the western Mediterranean basin. Its annual solid discharges vary between 2 and 20 Mt, with flood events responsible for more than 70% of these amounts. In the marine coastal area, close to the mouth, both flocculation and aggregation lead to the formation of fine-grained deposits, i.e. the prodelta. This area is characterized by sediment accumulation rates up to 20-50 cm yr(-1) and high accumulations of particle reactive contaminants such as...
Tipo: Text Palavras-chave: Sediment dynamics; Floods; Hydrodynamics; Radiotracers; Rhone River prodelta.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00006/11695/8479.pdf
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Modélisation du transport particulaire dans le Golfe du Lion en vue d'une application au devenir des traceurs radioactifs issus du Rhône ArchiMer
Dufois, Francois.
Among the contaminants introduced into the environment, the artificial radionuclides appear particularly important to take into account because of their chemical toxicity and/or of their radiotoxicity. Some radionuclides present a high affinity with particles so that the study of the sediment dynamics is a useful preliminary to the study of their dispersion on the open sea. This thesis is focused on the fate of sediments in the Gulf of Lions (NW Mediterranean) and in particular on the impact of the Rhone River, which is the main source of particulate matter in the Gulf of Lions. In order to study the sediment transport mechanisms on various space and time scales, this thesis is based on mathematical modelling. The hydro-sedimentary model set up in the Gulf...
Tipo: Text Palavras-chave: Waves; MARS 3D; Hydrodynamic; Radionuclides; Modelling; Sediment; Rhône prodelta; Gulf of Lions; Vagues; MARS 3D; Hydrodynamique; Radioéléments; Modélisation; Sédiment; Prodelta du Rhône; Golfe du Lion.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/these-6308.pdf
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Sand bodies at the shelf edge in the Gulf of Lions (Western Mediterranean): Deglacial history and modern processes ArchiMer
Bassetti, Maria-angela; Jouet, Gwenael; Dufois, Francois; Berne, Serge; Rabineau, Marina; Taviani, M.
The outer continental shelf of the Gulf of Lions is covered by thick, mainly regressive, sand deposits. A combination of seismic, sedimentological and geochronological methods allows us to demonstrate that a veneer of transgressive sand bodies, few m to less than 1 m thick, reworks these deposits. They take the form of sand ridges and transverse dunes that formed at different periods. In fact, the low-gradient outer shelf of the Gulf of Lions displays a complete record of deglacial history, including not only transgressive deposits that formed during sea-level rise, but also bedfonns that still evolve under episodic high-energy events that occur under more highstand conditions. Core lithology, C-14 dates and regional sea-level curve suggest that the...
Tipo: Text Palavras-chave: Gulf of Lions; Sand transport; Deglacial transgression; Outer shelf; Sand ridges.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2321.pdf
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Shelf-edge jet currents in the southern Benguela: a modelling approach ArchiMer
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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Wave- and current-induced bottom shear stress distribution in the Gulf of Lions ArchiMer
Dufois, Francois; Garreau, Pierre; Le Hir, Pierre; Forget, P.
Simulations of both currents and waves were performed throughout the year 2001 to assess the relative contribution of each to their overall erosive potential on the Gulf of Lions shelf. Statistical analysis of bottom shear stress (BSS) was compared to sediment grain-size distribution on the bottom. The hydrodynamic features of the bottom layer coincide with the distribution of surficial sediments, and three areas with different hydro-sedimentary characteristics were revealed. (i) The sandy inner shelf ( < 30 m) area is a high-energy-wave dominated area but may be subjected to intense current-induced BSS during on-shore winds along the coast and during continental winds mainly in the up-welling cells. (ii) The middle shelf (30-100 m) is a low-energy...
Tipo: Text Palavras-chave: Gulf of Lions; 3D modelling; Bottom shear stress; Sediment transport.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-6305.pdf
Registros recuperados: 11
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