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Registros recuperados: 79
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3D modelling of seasonal evolution of Loire and Gironde plumes on Biscay Bay continental shelf ArchiMer
Lazure, Pascal; Jegou, Anne-marie.
A 3D model of the Atlantic shelf has been developed and applied to study shelf dynamics and evolution of hydrology. The model takes the combined effects of tide, wind, river discharges and surface heat flux into account. Time scales vary from 1 day to several years. Following a brief description of the model and forcing variables, the behaviour of the Loire and Gironde plumes is described, first for winter and spring, then over a period of several years, under realistic forcing. The results show that plume evolution depends on the high Variability of river runoff and winds. Model simulations performed over 7 years (1990 to 1996) have highlighted several features of these plumes: 1) In early winter and periods of high river runoff, plumes usually spread...
Tipo: Text Palavras-chave: Panache; Modélisation; Dynamique du plateau continental; Golfe de Gascogne; River plume; Modelling; Shelf dynamics; Bay of Biscay.
Ano: 1998 URL: http://archimer.ifremer.fr/doc/1998/publication-847.pdf
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A 37 years hindcast of a coupled physical-biogeochemical model and its use for fisheries oceanography in the Bay of Biscay ArchiMer
Huret, Martin; Petitgas, Pierre; Struski, Caroline; Leger, Fabien; Sourisseau, Marc; Lazure, Pascal.
Overexploitation and climate change are increasingly causing unanticipated changes in marine ecosystems, such as higher variability in fish recruitment and shifts in species distribution, pressing for developing fisheries oceanography. In the meantime, operational oceanography rapidly progresses and its products become easy to access to a large community, among them fisheries scientists. Multiyear oceanographic reanalyses (hindcasts) were identified has a priority product by the ICES WG on Operational Oceanographic Products for Fisheries and Environment (WGOOFE). We performed a 37 years hindcast (1972-2008) run with a coupled physical-biogeochemical model (ECO-MARS3D) over the Bay of Biscay, using realistic meteorological and run-off forcing. We first...
Tipo: Text
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00023/13432/10442.pdf
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A 38 years hindcast of a coupled physical-biogeochemical model and derived indices for fisheries oceanography ArchiMer
Huret, Martin; Petitgas, Pierre; Sourisseau, Marc; Struski, Caroline; Leger, Fabien; Lazure, Pascal.
Operational oceanography rapidly progresses and its products become easy to access to a large community, among them fisheries scientists. The products cover both near real-time environment information (on scales of days to weeks) but also retrospective analysis providing long time series of environment parameters. Here we describe a 38 years hindcast of a coupled physical-biogeochemical model of the Bay of Biscay as well as the indices and major information that were derived from it.
Tipo: Text
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00023/13454/10466.pdf
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A coastal ocean model intercomparison study for a three-dimensional idealised test case ArchiMer
Tartinville, B; Deleersnijder, E; Lazure, Pascal; Proctor, R; Ruddick, Kg; Uittenbogaard, Re.
Several coastal ocean models have been used to compute the circulation on the Northwest European Continental Shelf. Five of them, developed within the European Union, are compared in the scope of an idealised three-dimensional test case, dealing with the geostrophic adjustment of a freshwater cylinder. As the central eddy adjusts, unstable baroclinic vortices start to grow. All the models are able to produce such unstable vortices. However, two of them produce an order-two instability, which is in accordance with a previous laboratory experiment, while the others exhibit an order-four instability. Using a simple scaling analysis, it is seen that the azimuthal wavenumber depends on the ratio of the kinetic energy to the available potential energy. It...
Tipo: Text Palavras-chave: Model intercomparison; Advection; Baroclinic instability; Geostrophic balance.
Ano: 1998 URL: http://archimer.ifremer.fr/doc/00448/55938/57485.pdf
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A HMM-based model to geolocate pelagic fish from high-resolution individual temperature and depth histories: European sea bass as a case study ArchiMer
Woillez, Mathieu; Fablet, Ronan; Tran-thanh Ngo,; Lalire, Maxime; Lazure, Pascal; De Pontual, Helene.
Numerous methods have been developed to geolocate fish from data storage tags. Whereas demersal species have been tracked using tide-driven geolocation models, pelagic species which undertake extensive migrations have been mainly tracked using light-based models. Here, we present a new HMM-based model that infers pelagic fish positions from the sole use of high-resolution temperature and depth histories. A key contribution of our framework lies in model parameter inference (diffusion coefficient and noise parameters with respect to the reference geophysical fields—satellite SST and temperatures derived from the MARS3D hydrodynamic model), which improves model robustness. As a case study, we consider long time series of data storage tags (DSTs) deployed on...
Tipo: Text Palavras-chave: Fish movement; Archival tagging; Migration; Population structure; Hidden Markov Model (HMM); State-space model.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00300/41097/40270.pdf
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A model of the general circulation in the Persian Gulf and in the Strait of Hormuz: Intraseasonal to interannual variability ArchiMer
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: http://archimer.ifremer.fr/doc/00244/35563/35324.pdf
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A multi-decadal hindcast of a physical–biogeochemical model and derived oceanographic indices in the Bay of Biscay ArchiMer
Huret, Martin; Sourisseau, Marc; Petitgas, Pierre; Struski, Caroline; Leger, Fabien; Lazure, Pascal.
Multiple year oceanographic simulations (hindcast) are identified as a priority oceanography product for fisheries and environment studies since they provide a unique continuous long-term dataset allowing integrated assessment of the ocean state and evolution. We performed a 37 year (1972–2008) hindcast run with a coupled physical–biogeochemical model in the Bay of Biscay. The coupled model and the hindcast configuration are described. A model skill assessment is performed with a large set of in-situ data. Average seasonal currents show major circulation patterns over the shelf. Among tracers, temperature and salinity have the best agreement, ahead of nitrates and silicates, chlorophyll, and finally phosphates and ammonium. For chlorophyll, improved...
Tipo: Text Palavras-chave: Physical-biogeochemical model; Hindcast; Skill assessment; Environmental indices; Seasonal pattern; Interannual variability; Fisheries oceanography; Bay of Biscay.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00114/22538/20237.pdf
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A Process Study of the Tidal Circulation in the Persian Gulf ArchiMer
Pous, Stephane; Carton, Xavier; Lazure, Pascal.
A homogeneous shallow-water model with free surface is used to model the tidal circulation in the Persian Gulf. The numerical finite-difference model includes harmonic diffusion of horizontal momentum and quadratic bottom friction, it has a 9 km mesh size and it is forced by 7 tidal components at its southern boundary. High precision bathymetric data are used to obtain the bottom topography. The numerical model is run for more than a year. The results are the following: 1) The model accurately reproduces the tidal phase and amplitude observed at 42 tidal gauges in the region. This accuracy is attributed to the presence of the 7 components which are able to interact nonlinearly; 2) The amphidromic points are also well positioned by the model due to a proper...
Tipo: Text Palavras-chave: Persian Gulf; Barotropic Tide; Hydrodynamical Modeling; Comparison with Data.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00284/39520/38013.pdf
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A Process Study of the Wind-Induced Circulation in the Persian Gulf ArchiMer
Pous, Stephane; Carton, Xavier; Lazure, Pascal.
A shallow-water model, coupled with a three dimensional, hydrostatic ocean model, is used to study the wind induced circulation, and the Shatt-al-Arab river plume expansion, in the Persian Gulf. The models are used in an idealized configuration. The following results are obtained: 1) with northwesterly winds, a double gyre is formed: this gyre is cyclonic in the south and anticyclonic in the north. Southeastward currents flow along the Iranian and Arabian coast where the wind stress at the surface dominates the pressure gradient related to the free surface slope, and conversely in the deeper region of the Gulf; 2) In the eastern part of the Gulf, the cyclonic gyre intensifies, as observed and reported in the literature; 3) For northwesterly winds, the...
Tipo: Text Palavras-chave: Persian Gulf; Wind-Induced Circulation; Hydrodynamical Modeling.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00284/39521/38014.pdf
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Advanced spectral analysis and cross correlation based on the empirical mode decomposition: application to the environmental time series ArchiMer
Ben Ismail, Dhouha Kbaier; Lazure, Pascal; Puillat, Ingrid.
Abstract—In marine sciences, time series are often nonlinear and nonstationary. Adequate and specific methods are needed to analyze such series. In this paper, an application of the Empirical Mode Decomposition method (EMD) associated to the Hilbert Spectral Analysis (HSA) is presented. Furthermore, EMD based Time Dependent Intrinsic Correlation (TDIC) analysis is applied to consider the correlation between two nonstationary time series. Four temperature time series obtained from automatic measurements in nearshore waters of the Réunion island are considered, recorded every ten minutes from July 2011 to January 2012. The application of the EMD on these series and the estimation of their power spectra using the HSA are illustrated. The authors identify...
Tipo: Text Palavras-chave: Augmented Dickey-Fuller tests; Cross correlation; Empirical mode decomposition (EMD); Hilbert spectral analysis (HSA); Hilbert-Huang transform (HHT); Stationarity; Time-dependent intrinsic correlation (TDIC); Time series; Wavelets.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00270/38077/36205.pdf
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Analysis of salinity measurements near islands on the French continental shelf of the Bay of Biscay ArchiMer
Lazure, Pascal; Jegou, Anne-marie; Kerdreux, Michel.
The Bay of Biscay is characterised by large fresh water inputs from two major rivers, the Loire and the Gironde, with a mean discharge of about 900 m(3)/s. To describe the spatial and temporal variability of the Loire and Gironde plumes, continuous salinity measurements were made at 4 locations on French coastal islands over periods lasting at least two years. These islands are located at a distance from the large local gradients linked to local inputs. Whereas sea surface salinity in the centre of the Bay of Biscay is 35.6, salinities at the coast vary between about 35 in summer to occasionally less than 30 in late winter or in spring. Minimum salinities do not occur at the same time along the coast, indicating a strong spatial gradient. Near the Loire...
Tipo: Text Palavras-chave: Bay of Biscay; Continental shelf; River plume; Seasonal variability; Salinity; Hydrology.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-3957.pdf
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Application of Hilbert-Huang decomposition to temperature and currents data in the Réunion island ArchiMer
Kbaier-ben Ismail, Dhouha; Lazure, Pascal; Puillat Felix, Ingrid.
In marine sciences, time series are often nonlinear and nonstationary. Their analysis faces new challenges and thus requires the implementation of adequate and specific methods. We use the Hilbert-Huang Transform (HHT) for the spectral analysis of high frequency sampled time series in near shore waters of the Réunion island, located in the Indian Ocean 700 km east of Madagascar. We focus particularly on automatic measurements of sea level fluctuations, temperature records and current data sets at four different stations in the island. We look at the contribution of different Intrinsic Mode Functions (IMFs) obtained by the Empirical Mode Decomposition (EMD) and also compare the Hilbert spectra with the wavelet spectra. The inertial wave and several...
Tipo: Text Palavras-chave: Cross correlation; Empirical mode decomposition (EMD); Hilbert spectral analysis (HSA); Hilbert-Huang transform (HHT); Stationarity; Time-dependent intrinsic correlation (TDIC); Time series; Wavelets.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00383/49392/49822.pdf
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Benthic metabolism in shallow coastal ecosystems of the Banc d'Arguin, Mauritania ArchiMer
Clavier, Jacques; Chauvaud, Laurent; Amice, Erwan; Lazure, Pascal; Van Der Geest, Matthijs; Labrosse, Pierre; Diagne, Ahmed; Carlier, Antoine; Chauvaud, Sylvain.
Benthic primary production and respiration were investigated at 4 sites representative of the major coastal communities bordering the Sahara Desert in the Banc d'Arguin, Mauritania, Western Africa. These sites correspond to intertidal Zostera noltii beds (270 km(2)), intertidal bare sediments (88 km(2)), subtidal Cymodocea nodosa beds (374 km(2)), and subtidal bare sediments (311 km(2)). At each site, production-irradiance relationships were established in situ in November 2008 and January 2010, and used to calculate daily carbon fluxes for these communities. In intertidal areas, compared to emersion, the gross maximal photosynthetic rates for Z. noltii bed and bare sediment communities were on average 8-and 7-fold higher during immersion, respectively;...
Tipo: Text Palavras-chave: Seagrass; Carbon metabolism; Intertidal; Subtidal; Respiration; Primary; Production; Western Africa.
Ano: 2014 URL: https://archimer.ifremer.fr/doc/00189/29987/28460.pdf
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Biophysical modelling of larval drift, growth and survival for the prediction of anchovy (Engraulis encrasicolus) recruitment in the Bay of Biscay (NE Atlantic) ArchiMer
Allain, Gwenhael; Petitgas, Pierre; Lazure, Pascal; Grellier, Patrick.
Fish recruitment is the result of the integration of small-scale processes affecting larval survival over a season and large oceanic areas. A hydrodynamic model was used to explore and model these physical-biological interaction mechanisms and then to perform the integration from individual to population scales in order to provide recruitment predictions for fisheries management. This method was applied to the case of anchovy (Engraulis encrasicolus) in the Bay of Biscay (NE Atlantic). The main data available to investigate survival mechanisms were past growth (otolith) records of larvae and juveniles sampled at sea. The drift history of these individuals was reconstructed by a backtracking procedure using hydrodynamic simulations. The relationships...
Tipo: Text Palavras-chave: Recruitment; Physical biological interactions; Individual based models; Biscay; Anchovy.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3422.pdf
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Bulletin d'information PREVIMER - Informations et analyses des eaux côtières. Janvier Février 2010 - n°12 ArchiMer
Lazure, Pascal; Huret, Martin; Gohin, Francis; Menesguen, Alain; Lecornu, Fabrice; Le Traon, Pierre-yves; Thomin, Pascale; Jegou, P.; Baraer, F.; Corre, Gilles; Louazel, Stephanie; Equipe projet PREVIMER.
Sommaire * Météo et débits des fleuves.....2 * Caractéristiques des masses d’eau côtières..............5 * Production biologique............11 * Rappel des objectifs du bulletin PREVIMER..................13 * Les moyens d’observations et de prévisions de l’état des mers côtières...........................13 * Glossaire..................................15
Tipo: Text
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00242/35367/33866.pdf
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Bulletin d'information PREVIMER - Informations et analyses des eaux côtières. Mars Avril 2009- n°7 ArchiMer
Lazure, Pascal; Huret, Martin; Gohin, Francis; Sourisseau, Marc; Saulquin, Bertrand; Lecornu, Fabrice; De Roeck, Yann-herve; Legrand, Jacques; Thomin, Pascale; Aoustin, Yannick; Jegou, P.; Baraer, F.; Le Stum, M.; Louazel, Stephanie; Equipe projet PREVIMER.
Sommaire * Météo, états de mer et débits des fleuves.....................2 * Caractéristiques des masses d’eau côtières..............6 * Production biologique............11 * Les faits marquants................12 * Rappel des objectifs du bulletin PREVIMER..................13 * Les moyens d’observations et de prévisions de l’état des mers côtières...........................13 * Glossaire..................................15
Tipo: Text
Ano: 2009 URL: http://archimer.ifremer.fr/doc/00242/35360/33860.pdf
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Circulation around La Reunion and Mauritius islands in the south-western Indian Ocean: A modeling perspective ArchiMer
Pous, Stephane; Lazure, Pascal; Andre, Gael; Dumas, Franck; Halo, Issufo; Penven, Pierrick.
Circulation around both islands is dominated by westward propagating features The predominant time scale of variability of currents and SSH is 60 days There is local generation of eddies in the lee of the islands due to topography
Tipo: Text Palavras-chave: Ocean circulation; Hydrodynamic model; La Reunion; Eddies; Rossby waves.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00195/30624/29073.pdf
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Circulation on the shelf and the upper slope of the Bay of Biscay ArchiMer
Le Boyer, Arnaud; Charria, Guillaume; Le Cann, Bernard; Lazure, Pascal; Marie, Louis.
Here, we used measurements taken with an array of 10 acoustic Doppler current profilers deployed from July 2009 to August 2011 to describe the tidally filtered circulation over the shelf and upper slope on the French side off the French coasts of the Bay of Biscay. The measurements provided an overview of the shelf and slope circulation throughout the entire water column over a large range of spatial and time scales. The average circulation over the shelf and upper slope of the Bay of Biscay was poleward following the topography with a speed of the order of 3 cm s(-1). This average circulation had marked seasonal variability. In summer, the currents were equatorward on the outer shelf near surface. Deeper in the water column, the flow remained poleward. In...
Tipo: Text Palavras-chave: Bay of Biscay; Observation; Shelf and slope circulation; Vertical profile; ADCP; Wind driven circulation.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00139/24976/26395.pdf
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Communication de l’information géographique maritime et côtière pour la gestion d’une crise environnementale : le naufrage du chimiquier « Ievoli Sun » en Centre Manche ArchiMer
Loubersac, Lionel; Lazure, Pascal; Dumas, Franck; Le Roux, Jean-francois; Riou, Philippe; Foucher, Eric; Guillaumont, Brigitte.
On the morning of the 31th October 2000, the Italian chemical tanker “Ievoli Sun” sank in the central Channel. Her cargo presented a risk of contamination for the marine environment and nearby coastal environment. From the moment the sinking was announced, Ifremer decided to implement, in almost real time, tools to produce and communicate environmental data. This paper presents the solutions chosen to develop: - a Geographic Information System to prepare maps, - a series of simulations for dispersion at sea of dissolved products - a general information web site structure (see http://www.ifremer.fr/envlit/surveillance/ievoli.htm). This paper will go beyond technical presentations of methods, tools and results obtained to take a critical look at the site’s...
Tipo: Text
Ano: 2003 URL: http://archimer.ifremer.fr/doc/00089/20054/17695.pdf
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Coupled 2-d and 3-d modeling of coastal hydrodynamics ArchiMer
Lazure, Pascal; Salomon, Jean-claude.
The hydrodynamics of coastal zones often reflect the combined action of tides, winds and density differences. Usual two-dimensional numerical models are only partly suited to the study of such mechanisms. A set of two 2-D and 3-D numerical models is described here. Its main characteristics are: an automatic coupling, a specific procedure for shoaling banks, a reduced vertical coordinate system, and a resolution by finite differences. As an example, the complete set is applied to the region of the Loire and Vilaine estuaries in South Brittany (France). Results prove to be coherent with experimental data and enhance our knowledge of the local hydrodynamics.
Tipo: Text
Ano: 1991 URL: http://archimer.ifremer.fr/doc/00101/21248/18862.pdf
Registros recuperados: 79
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