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Registros recuperados: 20 | |
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Ferron, Bruno. |
The increasing number of oceanic observations calls for the use of synthetic methods to provide consistent analyses of the oceanic variability that will support a better understanding of the underlying mechanisms. In this study, a 1/3 degrees eddy-permitting model of the North Atlantic (from 20 degrees S to 70 degrees N) is combined with a 4D-variational method to estimate the oceanic state from altimeter observations. This resolution allows a better extraction of the physical content of altimeter data since the model spatial scales are more consistent with the data than coarser assimilation exercises because of a lower error in model representativity. Several strategies for the assimilation window are tested through twin experiments carried out under the... |
Tipo: Text |
Palavras-chave: Ocean modelling; Data assimilation; Variational method; Meso-scale; Sea surface height; Heat transport; Meridional overturning. |
Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00044/15534/12956.pdf |
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Lavergne, C.; Vic, Clement; Madec, G; Roquet, F.; Waterhouse, A. F.; Whalen, C. B.; Cuypers, Y.; Bouruet‐aubertot, P.; Ferron, Bruno; Hibiya, T.. |
Vertical mixing is often regarded as the Achilles' heel of ocean models. In particular, few models include a comprehensive and energy‐constrained parameterization of mixing by internal ocean tides. Here, we present an energy‐conserving mixing scheme which accounts for the local breaking of high‐mode internal tides and the distant dissipation of low‐mode internal tides. The scheme relies on four static two‐dimensional maps of internal tide dissipation, constructed using mode‐by‐mode Lagrangian tracking of energy beams from sources to sinks. Each map is associated with a distinct dissipative process and a corresponding vertical structure. Applied to an observational climatology of stratification, the scheme produces a global three‐dimensional map of... |
Tipo: Text |
Palavras-chave: Ocean mixing; Internal tides; Parameterization; Energy dissipation. |
Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00624/73573/72943.pdf |
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Landeira, Jose Maria; Ferron, Bruno; Lunven, Michel; Morin, Pascal; Marie, Louis; Sourisseau, Marc. |
Phytoplankton blooms are usually dominated by chain-forming diatom species that can alter food pathways from primary producers to predators by reducing the interactions between intermediate trophic levels. The food-web modifications are determined by the length of the chains; however, the estimation is biased because traditional sampling strategies damage the chains and, therefore, change the phytoplankton size structure. Sedimentological studies around oceanic fronts have shown high concentrations of giant diatom mats (>1 cm in length), suggesting that the size of diatom chains is underestimated in the pelagic realm. Here, we investigate the variability in size and abundance of phytoplankton chains at the Ushant tidal front (NW France) using the Video... |
Tipo: Text |
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Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00186/29730/28148.pdf |
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Branellec, Pierre; Ferron, Bruno; Lherminier, Pascale. |
La campagne Ovide 4, réalisée du 9 juin au 10 juillet 2008 sur le N/O Thalassa, est la quatrième d'une série de 5 campagnes océanographiques dont le but est d'établir un observatoire de la variabilité climatique du tourbillon subpolaire de l'océan Atlantique Nord. Le projet Ovide est dirigé par Herlé Mercier et il est principalement financé par Ifremer, INSU (LEFE-IDAO) et UBO. Les trois premières campagnes Ovide ont été réalisées à la même période de l'année en 2002, 2004, 2006 et le long du même trajet entre l'extrémité sud-est du Groenland et la Péninsule Ibérique (section Ovide, également appelée A25 dans le programme CLIVAR) via la Mer d'Irminger, le Bassin d'Islande et le Bassin Ouest Européen, légèrement au nord de la section FourEx d'août 1997... |
Tipo: Text |
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Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00210/32124/30568.pdf |
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Forget, Gael; Ferron, Bruno; Mercier, Herle. |
Argo is a global array of profiling floats that provides temperature (T) and salinity (S) profiles from 2000 m to the surface every ten days with a nominal spatial resolution of 3 degrees. Here we present idealized experiments where the adjoint method is used to synthesize simulated sets of Argo profiles with a general circulation model, over a one-year period, in the North Atlantic. Using a number of drifting profilers consistent with Argo deployment objectives, the simulated array permits one to identify large-scale anomalies in the hydrography and circulation, despite the presence of a simulated eddy noise of large amplitude. Model dynamics provide an objective means to distinguish eddy noise from large-scale oceanic variability, and to infer the... |
Tipo: Text |
Palavras-chave: General circulation model; Argo; Twin experiment; 4DVAR; Data assimilation. |
Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-3721.pdf |
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Forget, Gael; Mercier, Herle; Ferron, Bruno. |
A set of Argo profiles collected in the North Atlantic between May 2002 and April 2003 is combined with a low-resolution general circulation model (GCM) using the adjoint method. Fitting the real hydrographic observations leads to vast improvements in the model circulation., including the sea surface height and the meridional heat transport. We find striking differences in basin-scale transports compared with previous assimilation experiments that use the same GCM and a similar spatial resolution. Based on forward modeling studies, it is argued that these differences are due to different assimilation experiment durations. Over 1 year, the hydrography interpolated with the GCM from Argo profiles better represents the contemporary structures than does a... |
Tipo: Text |
Palavras-chave: General circulation model; Argo; In situ observations; 4DVAR; Data assimilation. |
Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-3920.pdf |
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Bouruet-aubertot, Pascale; Cuypers, Yannis; Ferron, Bruno; Dausse, Denis; Menage, Olivier; Atmadipoera, Agus; Jaya, Indra. |
Microstructure measurements were performed along two sections through the Halmahera Sea and the Ombai Strait and at a station in the deep Banda Sea. Contrasting dissipation rates (𝜖) and vertical eddy diffusivities (K z ) were obtained with depth-averaged ranges of ∼[9×10−10−10−5] W kg− 1 and of ∼[1×10−5−2×10−3] m2 s− 1, respectively. Similarly, turbulence intensity, I=ϵ/(νN2) with ν the kinematic viscosity and N the buoyancy frequency, was found to vary seven orders of magnitude with values up to 107. These large ranges of variations were correlated with the internal tide energy level, which highlights the contrast between regions close and far from internal tide generations. Finescale parameterizations of 𝜖 induced by the breaking of... |
Tipo: Text |
Palavras-chave: Turbulence; Internal tides; Vertical mixing; Parameterization; Indonesian seas; Microstructure measurements. |
Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00441/55240/56792.pdf |
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Ferron, Bruno; Kokoszka, Florian; Mercier, Herle; Lherminier, Pascale. |
A total of 96 finestructure and 30 microstructure full-depth vertical profiles were collected along the A25 Greenland–Portugal Observatoire de la Variabilité Interannuelle et Décennale en Atlantique Nord (OVIDE) hydrographic line in 2008. The microstructure of the horizontal velocity was used to calculate turbulent kinetic energy dissipation rates εvmp, where vmp refers to the vertical microstructure profiler. The lowest dissipation values (εvmp < 0.5 × 10−10 W kg−1) are found below 2000 m in the Iberian Abyssal Plain and in the center of the Irminger basin; the largest values (>5 × 10−10 W kg−1) are found in the main thermocline, around the Reykjanes Ridge, and in a 1000-m-thick layer above the bottom near 48°N. The finestructure of density was used... |
Tipo: Text |
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Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00240/35130/33628.pdf |
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Xie, X. H.; Cuypers, Y.; Bouruet-aubertot, P.; Pichon, A.; Lourenco, A.; Ferron, Bruno. |
High-frequency mooring data were collected near the northern shelf edge of the Bay of Biscay to investigate the generation and propagation of internal tides and internal solitary waves (ISWs). During spring tide, strong nonlinear internal tides and large amplitude ISWs are observed every semidiurnal tidal period. While onshore propagation was expected since the mooring is located shoreward of the maximum internal tidal generation location, both onshore and seaward traveling internal tides are identified. Within a tidal period at spring tide, three ISW packets are observed. Like internal tides, different ISW packets have opposite (seaward and shoreward) propagating direction. Based on realistic hydrostatic HYCOM simulations, it is suggested that advection... |
Tipo: Text |
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Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00281/39237/37797.pdf |
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Ferron, Bruno; Aubertot, P. Bouruet; Cuypers, Y.; Schroeder, K.; Borghini, M.. |
The dissipation rate of turbulent kinetic energy ε and the associated diapycnal turbulent mixing is inferred from a set of microstructure observations collected over several cruises from year 2012 to 2014. The geographical distribution of ε highlights several regions of enhanced levels of turbulence ranging from 10−9 to 10−6 W kg−1: the Sicily Channel, the Corsica Channel, and the Ligurian Sea. Elsewhere, ε was small, often below 10−10 W kg−1. Below 1300 m, geothermal heating provides three-fold more buoyancy than small-scale turbulence. Geothermal heating and turbulent diffusion provide enough buoyancy to balance 15% to 50% of a mean yearly deep water formation rate of 0.9 to 0.3 sverdrup (106 m3/s), respectively. The remaining part has to eventually... |
Tipo: Text |
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Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00396/50695/51385.pdf |
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Ferron, Bruno; Marotzke, Jochem. |
World Ocean Circulation Experiment (WOCE) hydrographic sections and a sea-surface climatology are combined with a ocean general circulation model through a 4D-variational method to analyze the meridional overturning of the Indian Ocean. The regional model is run with realistic surface forcings over year 1995 for which most of WOCE Indian Ocean sections were made. The assimilation controls the initial temperature and salinity fields, surface forcings and open-boundary velocities, temperature and salinity. When no observations are assimilated, the model shows that the deep (below 1000 m) meridional overturning is weak compared to observation-based estimates. This is a common feature of general circulation models. In contrast, after the assimilation, the... |
Tipo: Text |
Palavras-chave: Overturn; Oceanographic surveys; Hydrographic data; Ocean circulation. |
Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/2003/publication-582.pdf |
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Xie, X. H.; Cuypers, Y.; Bouruet-aubertot, P.; Ferron, Bruno; Pichon, Annick; Lourenco, A.; Cortes, Norbert. |
Microstructure and fine-scale measurements collected in the central Bay of Biscay during the MOUTON experiment are analyzed to investigate the dynamics of internal waves and associated mixing. Large-amplitude internal tides (ITs) that excite internal solitary waves (ISWs) in the thermocline are observed. ITs are dominated by modes 3 and 4, while ISWs projected on mode 1 that is trapped in the thermocline. Therein, ITs generate a persistent narrow shear band, which is strongly correlated with the enhanced dissipation rate in the thermocline. This strong dissipation rate is further reinforced in the presence of ISWs. Dissipation rates during the period without ISWs largely agree with the MacKinnon-Gregg scaling proposed for internal wavefields dominated by a... |
Tipo: Text |
Palavras-chave: Internal tides; Solitary waves; Turbulence; Bay of Biscay. |
Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00151/26232/24299.pdf |
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Kokoszka, Florian; Conversano, Fabio; Ludicone, Daniele; Ferron, Bruno; Bouruet-aubertot, Pascale; Mc Millan, Justine. |
A dissection of the physics of the seasonal cycle of the oceanic upper layer stratification is necessary to improve climate predictions and to constrain the response of biogeochemical cycles to the climate change. Here we present a time series of vertical profiles of ε, the dissipation rate of turbulent kinetic energy, obtained from a microstructure profiler at a mid-latitude 75m-deep coastal site covering the destratification occurring during the the summer-to-winter. The main signature of the destratification is a progressive deepening of the mixed layer depth (MLD) from September to November, that finally extended to the bottom of the full water-column at the beginning of winter. By grouping the data into temporal and vertical bins we found that the... |
Tipo: Text |
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Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00662/77416/79078.pdf |
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Ferron, Bruno; Mercier, Herle; Speer, Kevin; Gargett, Ann; Polzin, Kurt. |
The Romanche Fracture Zone is a major gap in the Mid-Atlantic Ridge at the equator, which is deep enough to allow significant eastward flows of Antarctic Bottom Water from the Brazil Basin to the Sierra Leone and Guinea Abyssal Plains. While flowing through the Romanche Fracture Zone, bottom-water properties are strongly modified due to intense vertical mixing. The diapycnal mixing coefficient in the bottom water of the Romanche Fracture Zone is estimated by using the finestructure of CTD profiles, the microstructure of high-resolution profiler data, and by constructing a heat budget from current meter data. The finestructure of density profiles is described using the Thorpe scales L-T. It is shown from microstructure data taken in the bottom water that... |
Tipo: Text |
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Ano: 1998 |
URL: https://archimer.ifremer.fr/doc/00447/55830/62131.pdf |
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Ferron, Bruno; Mercier, Herle; Treguier, Anne-marie. |
This paper investigates the dynamics of the Antarctic Bottom Water (AABW) flow through the Romanche Fracture Zone (RFZ) in a primitive equation model with a high horizontal and vertical resolution. Two examples of Rows over simple bathymetries show that a reduced gravity model captures the essential dynamics of the primitive equation model. The reduced gravity model is then used as a tool to identify what are the bathymetric structures (sills, narrows) that mostly constrain the AABW flow through the RFZ. When only these structures are represented in the primitive equation model, the AABW how is shown to be coherent with observations (transports, density and velocity structures). |
Tipo: Text |
Palavras-chave: Circulation model; Fracture zone; Bottom water; Bathymetry. |
Ano: 2000 |
URL: http://archimer.ifremer.fr/doc/2000/publication-802.pdf |
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Copard, K.; Colin, C.; Frank, N.; Jeandel, C.; Montero-serrano, J-c; Reverdin, G.; Ferron, Bruno. |
Nd isotopic compositions (epsilon Nd) of seawater profiles and deep-sea corals collected off the coast of Iberia and from the Bay of Biscay were measured (1) to constrain the Nd isotopic composition of water masses along the southwest European margin, (2) to track the Mediterranean Outflow Water (MOW) during its northward propagation, and (3) to establish hydrological changes during the last 1500 years. The Eastern North Atlantic Central Water (ENACW) is characterized by Nd isotopic composition of around -12.0. Mediterranean Sea Water (MSW) is collected from 800 and 1200 m depth and is characterized by epsilon Nd values ranging from -10.9, off the coast of Iberia, to -11.6 in the Bay of Biscay. These epsilon Nd results suggest a strong dilution of the pure... |
Tipo: Text |
Palavras-chave: European margin; Nd isotopic composition; Deep‐sea corals; Water masses. |
Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00040/15108/12571.pdf |
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Fer, Ilker; Bosse, Anthony; Ferron, Bruno; Bouruet-aubertot, Pascale. |
Ocean microstructure, current and hydrography observations from June 2016 are used to characterize the turbulence structure of the Lofoten Basin Eddy (LBE), a long-lived anticyclone in the Norwegian Sea. The LBE had a azimuthal peak velocity of 0.8 ms−1 at 950 m depth and 22 km radial distance from its center, and a core relative vorticity reaching -0.7 f ( f is the local Coriolis parameter). When contrasted to a reference station in a relatively quiescent part of the basin, the LBE was significantly turbulent between 750 and 2000 m, exceeding the dissipation rates (ɛ) in the reference station by up to two orders of magnitude. Dissipation rates were elevated particularly in the core and at the rim below the swirl velocity maximum, reaching 10−8 Wkg–1. The... |
Tipo: Text |
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Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00437/54836/56312.pdf |
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Daniault, Nathalie; Mercier, Herle; Lherminier, Pascale; Sarafanov, Artem; Falina, Anastasia; Zunino, Patricia; Perezf, Fiz F.; Rios, Aida F.; Ferron, Bruno; Huck, Thierry; Thierry, Virginie; Gladyshev, Sergey. |
The decadal mean circulation in the northern North Atlantic was assessed for the early 21st century from repeated ship-based measurements along the Greenland-Portugal OVIDE line, from satellite altimetry and from earlier reported transports across 59.5°N and at the Greenland-Scotland sills. The remarkable quantitative agreement between all data sets allowed us to draw circulation pathways with a high level of confidence. The North Atlantic Current (NAC) system is composed of three main branches, referred to as the northern, central and southern branches, which were traced from the Mid-Atlantic Ridge (MAR), to the Irminger Sea, the Greenland-Scotland Ridge and the subtropical gyre. At OVIDE, the northern and central branches of the NAC fill the whole water... |
Tipo: Text |
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Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00345/45569/45177.pdf |
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Mercier, Herle; Lherminier, Pascale; Sarafanov, Artem; Gaillard, Fabienne; Daniault, Nathalie; Desbruyeres, Damien; Falina, Anastasia; Ferron, Bruno; Gourcuff, Claire; Huck, Thierry; Thierry, Virginie. |
The meridional overturning circulation (MOC) in the North Atlantic transports heat from the subtropics to high latitudes and hence plays an important role in the Earth’s climate. A region crucial for the MOC is the northern North Atlantic and the adjacent Nordic Seas, where waters transported northward in the MOC upper limb progressively cool, gain density and eventually sink. Here we discuss the variability of the gyre circulation, the MOC and heat flux as quantified from a joint analysis of hydrographic and velocity data from six repeats of the Greenland to Portugal OVIDE section (1997–2010), satellite altimetry and Argo float measurements. For each repeat of the OVIDE section, the full-depth absolute circulation and transports were assessed using an... |
Tipo: Text |
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Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00165/27583/25742.pdf |
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Ferron, Bruno; Kokoszka, Florian; Mercier, Herle; Lherminier, Pascale; Huck, Thierry; Rios, Aida; Thierry, Virginie. |
The variability of the turbulent kinetic energy dissipation due to internal waves is quantified using a finescale parameterisation applied to the A25 Greenland-Portugal transect repeated every two years from 2002 to 2012. The internal wave velocity shear and strain are estimated for each cruise at 91 stations from full depth vertical profiles of density and velocity. The 2002–2012 averaged dissipation rate, <ε2002–2012>, in the upper ocean lies in the range 1–10 × 10-10 W kg-1. At depth, <ε2002–2012> is smaller than 1 × 10-10 W kg-1 except over rough topography found at the continental slopes, the Reykjanes Ridge and in a region delimited by the Azores-Biscay Rise and Eriador Seamount. There, the vertical energy flux of internal waves is... |
Tipo: Text |
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Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00333/44463/44141.pdf |
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Registros recuperados: 20 | |
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