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| Registros recuperados: 23 | |
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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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| Colin De Verdiere, Alain; Huck, Thierry; Pogossian, Souren; Ollitrault, Michel. |
| The vertically integrated potential energy of an incompressible stratified fluid formulated in density coordinates can be simply written as a weighted vertical sum of the squares of the vertical displacements of density surfaces, a general expression valid for arbitrary displacements. The sum of this form of potential energy and kinetic energy is then a conserved quantity for the multilayer shallow water model. The formulation in density coordinates is a natural one to find the Lorenz reference state of available potential energy (APE).We describe the method to compute the APE of an ocean state and provide two applications. The first is the classical double-gyre, wind-driven circulation simulated by a shallow water model at high resolution.We show that the... |
| Tipo: Text |
Palavras-chave: Energy transport; Ocean circulation; Ocean dynamics; Isopycnal coordinates. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00464/57521/59707.pdf |
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| Sévellec, Florian; Naveira Garabato, A. C.; Huck, Thierry. |
| The impact of mesoscale eddy turbulence on long-term, climatic variability in the ocean's buoyancy structure is investigated using observations from a mooring deployed in the Drake Passage, Southern Ocean. By applying the Temporal-Residual-Mean framework and characterizing the variance contributors and the buoyancy variance budget, we identify the main source and sink of long-term buoyancy variance. Long-term buoyancy variance amplitude is set by long-term vertical velocity fluctuations acting on the steady stratification. This baro-clinic buoyancy flux is also the main source of the variance, indicative of the effect of large-scale baroclinic instability. This source is balanced by a sink of long-term buoyancy variance associated with the vertical... |
| Tipo: Text |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00658/77057/78356.pdf |
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| Sevellec, Florian; Huck, Thierry. |
| A weakly damped mode of variability, corresponding to the oceanic signature of the Atlantic multidecadal oscillation (AMO) was found through the linear stability analysis of a realistic ocean general circulation model. A simple two-level model was proposed to rationalize both its period and damping rate. This model is extended here to three levels to investigate how the mode can draw energy from the mean flow, as found in various ocean and coupled models. A linear stability analysis in this three-level model shows that the positive growth rate of the oscillatory mode depends on the zonally averaged isopycnal slope. This mode corresponds to a westward propagation of density anomalies in the pycnocline, typical of large-scale baroclinic Rossby waves. The... |
| Tipo: Text |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00281/39189/37745.pdf |
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| Herbette, Steven; Hochet, Antoine; Huck, Thierry; Colin De Verdiere, Alain; Collin, Jeremy; Shillington, Frank. |
| When a source-sink dipole forces a fluid on a beta-plane limited by a western boundary, the linear steady solution can be obtained analytically and consists of zonally elongated gyres that extend west of the forcing and close as western boundary currents. The nondimensional parameter Ro(upsilon) = U/(4 beta a(2)) (with U the zonal velocity of the flow and 2a the distance between the source and sink) is used to characterize the nonlinearity of the flow. When Ro(upsilon) reaches 0.1, the numerical shallow-water solution shows that the configuration with the source to the north of the sink becomes unstable, while the reverse configuration remains steady. Indeed, that reverse configuration remains steady for much larger values of the nonlinearity parameter... |
| Tipo: Text |
Palavras-chave: Beta-plane double-gyre; Source-sink rotating tank experiments; Jet instability; Hopf bifurcation. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00211/32182/30652.pdf |
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| Dobler, Delphine; Huck, Thierry; Maes, Christophe; Grima, Nicolas; Blanke, Bruno; Martinez, Elodie; Ardhuin, Fabrice. |
| In the open ocean, floating surface debris such as plastics concentrate in five main accumulation zones centered around 30° latitude, far from highly turbulent areas. Using Lagrangian advection of numerical particles by surface currents from ocean model reanalysis, previous studies have shown long-distance connection from the accumulation zones of the South Indian to the South Pacific oceans. An important physical process affecting surface particles but missing in such analyses is wave-induced Stokes drift. Taking into account surface Stokes drift from a wave model reanalysis radically changes the fate of South Indian particles. The convergence region moves from the east to the west of the basin, so particles leak to the South Atlantic rather than the... |
| Tipo: Text |
Palavras-chave: Marine debris; Microplastics; Stokes drift; Indian Ocean; Lagrangian analysis; Ocean surface pathways. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00512/62320/69273.pdf |
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| Sevellec, Florian; Huck, Thierry; Jelloul Mahdi, Ben. |
| Centennial oscillations of the ocean thermohaline circulation are studied in a 2-D latitude-depth model under mixed boundary conditions (i.e. restoring surface temperature and prescribed freshwater flux). The oscillations are revealed through linear stability analysis of a steady state obtained in a single hemisphere configuration. A density variance budget is performed and helps determine the physical processes sustaining these oscillations: the restoring surface temperature appears as a source of density variance - this is a consequence of positively-correlated temperature and salinity anomalies. A minimal model, the Howard-Malkus loop oscillator, enables us to understand physically the oscillatory and growth mechanisms. The centennial oscillation is... |
| Tipo: Text |
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| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-6335.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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| Arzel, Olivier; Huck, Thierry. |
| Atmospheric stochastic forcing associated with the North Atlantic Oscillation (NAO) and intrinsic ocean modes associated with the large-scale baroclinic instability of the North Atlantic Current (NAC) are recognized as two strong paradigms for the existence of the Atlantic Multidecadal Oscillation (AMO). The degree to which each of these factors contribute to the low-frequency variability of the North Atlantic is the central question in this paper. This issue is addressed here using an ocean general circulation model run under a wide range of background conditions extending from a super-critical regime where the oceanic variability spontaneously develops in the absence of any atmospheric noise forcing to a damped regime where the variability requires some... |
| Tipo: Text |
Palavras-chave: Instability; Rossby waves; Climate variability; Interdecadal variability; Multidecadal variability; North Atlantic Oscillation. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00599/71138/69452.pdf |
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| Sevellec, Florian; Huck, Thierry; Colin De Verdiere, Alain. |
| The freshwater flux intensity is used as the main control parameter to destabilize the ThermoHaline Circulation (THC): as it increases, the classical bifurcation scenario, thermal stable steady state, millennial oscillation and haline stable steady state are reproduced in a 2D zonally-averaged ocean model under mixed boundary conditions. Both bifurcations arise through global bifurcations leading to an infinite period of the limit cycle. Here we highlight a centennial oscillation important for the instability of the thermal phase of the millennial oscillation and which could be considered as a precursor to the collapse of the THC. It is suggested that the existence or the absence of this centennial oscillation leads to dramatic changes in the collapse time... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00038/14912/12623.pdf |
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| Arzel, Olivier; Huck, Thierry. |
| A simplified coupled ocean-atmosphere model, consisting of a one-layer bidimensional ocean model and a one-layer unidimensional energy balance atmospheric model [J. Clim. 13 (2000) 232] is used to study the unstable interactions between zonal winds and ocean gyres. In a specific range of parameters, decadal variability is found. Anomalies, quite homogeneous zonally, show small-scale wavelength in latitude: perturbations emerge and grow at the southern limb of the intergyre boundary and propagate southward before decaying. The wind stress anomalies are proportional to the meridional gradient of the atmospheric temperature anomalies: this ratio acts as a positive amplification factor, as confirmed by a parameter sensitivity analysis. Assuming... |
| Tipo: Text |
Palavras-chave: Ocean atmosphere system; Air sea interaction; Air sea coupling; Ocean circulation. |
| Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/2003/publication-647.pdf |
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| Lherminier, Pascale; Mercier, Herle; Huck, Thierry; Gourcuff, Claire; Perez, Fiz F.; Morin, Pascal; Sarafanov, Artem; Falina, Anastasia. |
| The horizontal circulation of the subpolar gyre and the Meridional Overturning Circulation (MOC) are investigated here by comparing two snapshots of the North Atlantic as delivered by two hydrographic sections between Greenland and Portugal. The corresponding cruises were carried out in June–July 2002 and June–July 2004 on R/V Thalassa within the framework of the Ovide project. The absolute transports in June 2004 are described in detail, and then compared with transports in June 2002. The MOC (in density coordinates), driven by the volume balance between the northward North Atlantic Current (NAC) and the net southward export of dense water from the subpolar gyre, did not change: View the MathML source (1 Sv=106 m3 s−1). Its upper limb, above σ1=32.1, is... |
| Tipo: Text |
Palavras-chave: North Atlantic; Subpolar gyre; Meridional Overturning Circulation; OVIDE; Hydrology; ADCP. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00011/12272/9057.pdf |
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| Maes, C.; Grima, N.; Blanke, Bruno; Martinez, E.; Paviet-salomon, T.; Huck, Thierry. |
| We study the dispersion and convergence of marine floating material by surface currents from a model reanalysis that represents explicitly mesoscale eddy variability. Lagrangian experiments about the long-term evolution (29 years) of an initially homogeneous concentration of particles are performed at global scale with horizontal current at ¼° resolution and refreshed daily over the 1985-2013 period. Results confirm and document the five known sites of surface convergence at the scale of individual oceanic basins, but also reveal a convergent pathway connecting the South Indian subtropical region with the convergence zone of the South Pacific through the Great Australian Bight, the Tasman Sea and the southwest Pacific Ocean. This “super-convergent” pathway... |
| Tipo: Text |
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| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00425/53631/54461.pdf |
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| Huck, Thierry; Colin De Verdiere, Alain; Estrade, P.; Schopp, Richard. |
| Low-frequency variations of the large-scale ocean circulation in the Atlantic are reconstructed from NODC pentadal anomalies of temperature and salinity from 1955 to 1998 based on hydrographic data, in addition to atmospheric reanalysis surface forcing. Diagnostic ocean circulations are estimated from simple methods using dynamical model integrations: namely diagnostic, robust diagnostic, and short prognostic. Mean transports of heat and mass are sensitive to the method and model configuration, but their decadal variability is much more coherent and does not depend explicitly on the variations of the surface forcing, its influence being imprinted in the thermohaline structure. Multidecadal variations are of the order of 20%, with large transports in the... |
| Tipo: Text |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6116.pdf |
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| Zhang, Yurui; Huck, Thierry; Lique, Camille; Donnadieu, Yannick; Ladant, Jean-baptiste; Rabineau, Marina; Aslanian, Daniel. |
| The early Eocene (∼55 Ma) was the warmest period of the Cenozoic and was most likely characterized by extremely high atmospheric CO2 concentrations. Here, we analyze simulations of the early Eocene performed with the IPSL-CM5A2 Earth system model, set up with paleogeographic reconstructions of this period from the DeepMIP project and with different levels of atmospheric CO2. When compared with proxy-based reconstructions, the simulations reasonably capture both the reconstructed amplitude and pattern of early Eocene sea surface temperature. A comparison with simulations of modern conditions allows us to explore the changes in ocean circulation and the resulting ocean meridional heat transport. At a CO2 level of 840 ppm, the early Eocene simulation is... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75529/76436.pdf |
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| Billant, Andre; Branellec, Pierre; Huck, Thierry. |
| La campagne Ovide 2 est la deuxième d'une série de campagnes océanographiques dont le but est d'établir un observatoire de la variabilité climatique du tourbillon subpolaire de l'océan Atlantique Nord. La première campagne Ovide 1 a été réalisée à la meme période de l'année en 2002. Des mesures d'hydrologie, géochimie et courant ont été réalisées en 119 stations entre l'extrémité sud-est du Groenland et la Péninsule Ibérique. La répétition de campagnes le long de ce trajet tous les deux ans pendant une période de 10 ans permet de documenter l'évolution des caractéristiques des masses d'eau, et de résoudre les fluctuations à basse fréquence de la cellule méridienne de circulation, et du transport de chaleur vers l'Europe. Ce projet s'intègre dans le... |
| Tipo: Text |
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| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/00210/32100/30558.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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| Hochet, Antoine; Huck, Thierry; Arzel, Olivier; Sevellec, Florian; Colin De Verdiere, Alain; Mazloff, Matthew; Cornuelle, Bruce. |
| The North Atlantic is characterized by basin-scale multidecadal fluctuations of the sea surface temperature with periods ranging from 20 to 70 years. One candidate for such a variability is a large-scale baroclinic instability of the temperature gradients across the Atlantic associated with the North Atlantic Current. Because of the long time scales involved, most of the studies devoted to this problem are based on low resolution numerical models leaving aside the effect of explicit meso-scale eddies. How high-frequency motions associated with the meso-scale eddy field affect the basin-scale low-frequency variabiliy is the central question of this study. This issue is addressed using an idealized configuration of an Ocean General Circulation Model at... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00635/74701/74640.pdf |
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| Registros recuperados: 23 | |
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