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Registros recuperados: 22
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A direct determination of the World Ocean barotropic circulation ArchiMer
De Verdiere, Alain Colin; Ollitrault, Michel.
The time-mean Argo float displacements and the World Ocean Atlas 2009 temperature–salinity climatology are used to obtain the total, top to bottom, mass transports. Outside of an equatorial band, the total transports are the sum of the vertical integrals of geostrophic- and wind-driven Ekman currents. However, these transports are generally divergent, and to obtain a mass conserving circulation, a Poisson equation is solved for the streamfunction with Dirichlet boundary conditions at solid boundaries. The value of the streamfunction on islands is also part of the unknowns. This study presents and discusses an energetic circulation in three basins: the North Atlantic, the North Pacific, and the Southern Ocean. This global method leads to new estimations of...
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Ano: 2016 URL: http://archimer.ifremer.fr/doc/00309/42033/41332.pdf
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ANDRO: An Argo - based deep displacement atlas ArchiMer
Ollitrault, Michel; Rannou, Philippe.
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00360/47078/46991.pdf
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ANDRO: An Argo-Based Deep Displacement Dataset ArchiMer
Ollitrault, Michel; Rannou, Jean Philippe.
During the first decade of the twenty-first century, more than 6000 Argo floats have been launched over the World Ocean, gathering temperature and salinity data from the upper 2000 m, at a 10-day or so sampling period. Meanwhile their deep displacements can be used to map the ocean circulation at their drifting depth (mostly around 1000 m). A comprehensive processing of the whole Argo dataset collected prior to 1 January 2010 has been performed to produce a world-wide dataset of deep displacements. This numerical atlas, named ANDRO, after a traditional dance of Brittany meaning a swirl, comprises some 600 000 deep displacements. These displacements, based on Argo or GPS surface locations only, have been fully checked and corrected for possible errors found...
Tipo: Text Palavras-chave: Lagrangian circulation/transport; Large-scale motions; Ocean circulation.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00138/24901/22994.pdf
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ANDRO Dataset contents and format ArchiMer
Ollitrault, Michel; Rannou, Jean-philippe.
Tipo: Text
Ano: 2013 URL: https://archimer.ifremer.fr/doc/00360/47126/47066.pdf
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Available Potential Energy in Density Coordinates ArchiMer
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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Complementary study n°2 search of the AF447 wreckage area ArchiMer
Ollitrault, Michel; Reynaud, Thierry.
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00032/14279/11556.pdf
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Estimating the wreckage location of the Rio-Paris af447 ArchiMer
Ollitrault, Michel; Blanke, Bruno; Chen, Changsheng; Diansky, Nicolai; Drevillon, Marie; Greiner, Eric; Lefevre, Fabien; Limeburner, Richard; Lezaud, Pascal; Louazel, Stéphanie; Nurser, George; Paradis, Denis; Scott, Robert.
Tipo: Text Palavras-chave: Current; Equator; Wind; RIO-PARIS AF447.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00027/13777/10915.pdf
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Evolution of Intermediate Water Masses Based on Argo Float Displacements ArchiMer
Sevellec, Florian; Colin De Verdiere, Alain; Ollitrault, Michel.
The evolution and dispersion of intermediate water masses in the ocean interior is studied. To this purpose, an empirical statistical model of Lagrangian tracers at a constant depth level is developed. The model follows the transfer operator based on 10-day deep displacements of Argo floats at; similar to 1000m depth. An asymptotic analysis of the model shows the existence of 10 principal stationary points (the 10 locations attract asymptotically 97% of the tracers). It takes; 1000 years to reach this asymptotic regime relevant for estimating the stationary points. For Lagrangian floats, the concept of attractor needs to be generalized in a statistical sense (versus deterministic), except for a few places in the ocean. In this new framework, a tracer has a...
Tipo: Text Palavras-chave: Dynamics; Large-scale motions; In situ oceanic observations; Statistical techniques; Ocean models.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00393/50450/51180.pdf
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Interocean exchanges and the spreading of Antarctic Intermediate Water south of Africa ArchiMer
Rusciano, Emanuela; Speich, Sabrina; Ollitrault, Michel.
Argo hydrographic profiles collected from 2004 to 2011 in the southeast Atlantic sector of the Southern Ocean are used in combination with hydrographic transects to describe the characteristics of Antarctic Intermediate Water (AAIW) in the region. Making use of the recently developed ANDRO velocity data set, we estimate the evolution of the dynamical properties of different AAIW varieties along their pathways within the isoneutral layer (27.1 < gamma(n) < 27.6). Three different regional varieties of intermediate water converge in the southeast Atlantic: Atlantic AAIW (A-AAIW, characterized by S <= 34.2), Indian AAIW (I-AAIW, S >= 34.3), and a previously unknown variety that we named Indo-Atlantic intermediate water (IA-AAIW, 34.2 < S <...
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Ano: 2012 URL: http://archimer.ifremer.fr/doc/00106/21719/19298.pdf
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Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic ArchiMer
Nunez Riboni, Ismael; Boebel, Olaf; Ollitrault, Michel; You, Yuzhu; Richardson, Philip; Davis, Russ.
This study combines float data from different projects collected between 1991 and 2003 in the South Atlantic to describe the flow of Antarctic Intermediate Water (AAIW). Velocity space-time averages are calculated for various grid resolutions and with cells deformed to match the bathymetry, f/H or f/h (with H being the water depth and It being the thickness of the AAIW layer). When judged by the degree of alignment between respective isolines and the resulting average velocity fields, the best grid is based on a nominal cell size of 3&DEG; (latitude) by 4&DEG; (longitude) with cell shapes deformed according to f/h. Using this grid, objectively estimated mean currents (and their associated errors), as well as meridional and zonal volume transports...
Tipo: Text Palavras-chave: Objective analysis; Transports; Lagrangian circulation; South Atlantic; Neutral density surfaces; Floats; Antarctic Intermediate Water ( AAIW ).
Ano: 2005 URL: https://archimer.ifremer.fr/doc/2005/publication-781.pdf
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Lagrangian observations in the Intermediate Western Boundary Current of the South Atlantic ArchiMer
Legeais, Jean-francois; Ollitrault, Michel; Arhan, Michel.
Subsurface float measurements at 800 m depth carried out from 1994 to 2003 in the Brazil Basin are used to characterise the equatorward Intermediate Western Boundary Current (IWBC) and its connections to the ocean interior. Transversally, the boundary flow is less than 100 km wide, and most intense at 10-20 km from the 800 m isobath. Its average velocities range from similar to 0.1 ms(-1) to 0.3 ms(-1) depending on latitude, with individual daily values as high as 0.7 ms(-1). The flow meridional extent exhibits 3 contrasted domains: (i) from 27 degrees S to the Vitoria-Trindade Ridge at 20 degrees 30'S, the boundary flow intensifies northward along a relatively smooth topography. A counter current adjacent to it on its seaward side feeds it with...
Tipo: Text Palavras-chave: Brazil basin; Intermediate water; Western boundary current.
Ano: 2013 URL: https://archimer.ifremer.fr/doc/00134/24561/22690.pdf
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MARVOR ou la liberté sous surveillance ArchiMer
Ollitrault, Michel.
Depuis le début des années 70, des flotteurs dérivant librement en profondeur s'utilisent pour décrire les mouvements des "particules" d'eau. En effet ces flotteurs se stabilisent naturellement à une immersion donnée où ils sont alors entraînés par les mouvements des masses d'eaux environnantes.
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Ano: 1993 URL: http://archimer.ifremer.fr/doc/1993/publication-7468.pdf
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Meridional Overturning and Heat Transport From Argo Floats Displacements and the Planetary Geostrophic Method (PGM): Application to the subpolar North Atlantic ArchiMer
Colin De Verdiere, Alain; Meunier, Thomas; Ollitrault, Michel.
A direct method is presented to obtain the meridional overturning and heat transport in oceanic basins from observations under the sole assumptions of geostrophy and hydrostatics. The method is made possible because of the rising Argo float displacements database that can provide a reference level at 1000 dbar for the time mean circulation at 1 degrees x 1 degrees resolution. To achieve the overturning and heat transport objectives, the absolute geostrophic time mean circulation must have nondivergent barotropic transports and this requires the solutions of two Poisson equations with suitable boundary conditions, one for the geopotential at 1000 dbar and one for the barotropic stream function. Applied to the subpolar Atlantic for the period 2000-2009, an...
Tipo: Text Palavras-chave: Oceanic heat transport; Meridional overturning; Subpolar Atlantic.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00589/70139/68105.pdf
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Open ocean regimes of relative dispersion ArchiMer
Ollitrault, Michel; Gabillet, Céline; De Verdiere, Alain Colin.
As two fluid particles separate in time, the entire spectrum of eddy motions is being sampled from the smallest to the largest scales. In large-scale geophysical systems for which the Earth rotation is important, it has been conjectured that the relative diffusivity should vary respectively as D-2 and D-4/3 for distances respectively smaller and larger than a well-defined forcing scale of the order of the internal Rossby radius (with D the r.m.s. separation distance). Particle paths data from a mid-latitude float experiment in the central part of the North Atlantic appear to support these statements partly: two particles initially separated by a few km within two distinct clusters west and east of the mid-Atlantic ridge, statistically dispersed following a...
Tipo: Text Palavras-chave: Taylor dispersion; Dispersion; Atlantic circulation; Particule pairs.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-456.pdf
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Recherche de l'épave du vol AF447: études complémentaires ArchiMer
Ollitrault, Michel.
Tipo: Text
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00027/13778/10916.pdf
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South Atlantic mass transports obtained from subsurface float and hydrographic data ArchiMer
Rodrigues, Regina R.; Wimbush, Mark; Watts, D. Randolph; Rothstein, Lewis M.; Ollitrault, Michel.
Mean total (barotropic + baroclinie) mass transports of the oceanic top 1000 dbar are estimated for two regions of the South Atlantic between 18 degrees S and 47 degrees S. These transports are obtained by using Gravest Empirical Mode (GEM) fields calculated from historical hydrography with temperature and position data from quasi-isobaric subsurface floats deployed from 1992 through 2001. The float-GEM-estimated total mass transports reveal a Brazil Current with a southward flow of 20.9 Sv at 30 degrees S and 46 Sv at 35 degrees S (1 Sverdrup, Sv = 10(6) m(3) s(-1)). Two recirculation cells are identified in the southwest corner of the subtropical gyre north of 40 degrees S, one centered at 48 degrees W, 37 degrees S recirculating 28.5 Sv and another...
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00043/15391/12816.pdf
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The mid-depth circulation of the northwestern tropical Atlantic observed by floats ArchiMer
Lankhorst, Matthias; Fratantoni, David; Ollitrault, Michel; Richardson, Philip; Send, Uwe; Zenk, Walter.
A comprehensive analysis of velocity data from subsurface floats in the northwestern tropical Atlantic at two depth layers is presented: one representing the Antarctic Intermediate Water (AAIW, pressure range 600-1050dbar), the other the upper North Atlantic Deep Water (uNADW, pressure range 1200-2050dbar). New data from three independent research programs are combined with previously available data to achieve blanket coverage in space for the AAIW layer, while coverage in the uNADW remains more intermittent. Results from the AAIW` mainly confirm previous studies on the mean flow, namely the equatorial zonal and the boundary currents, but clarify details on pathways, mostly by virtue of the spatial data coverage that sets float observations apart from e.g....
Tipo: Text Palavras-chave: Equatorial currents; North Atlantic Deep Water; Antarctic Intermediate Water; Tropical Atlantic; Floats.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6815.pdf
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The Ocean General Circulation near 1000-m Depth ArchiMer
Ollitrault, Michel; Colin De Verdiere, Alain.
The mean ocean circulation near 1000-m depth is estimated with 100-km resolution from the Argo float displacements collected before 1 January 2010. After a thorough validation, the 400 000 or so displacements found in the 950–1150 dbar layer and with parking times between 4 and 17 days allow the currents to be mapped at intermediate depths with unprecedented details. The Antarctic Circumpolar Current (ACC) is the most prominent feature, but western boundary currents (and their recirculations) and alternating zonal jets in the tropical Atlantic and Pacific are also well defined. Eddy kinetic energy (EKE) gives the mesoscale variability (on the order of 10 cm2 s−2 in the interior), which is compared to the surface geostrophic altimetric EKE showing e-folding...
Tipo: Text Palavras-chave: Circulation; Dynamics; Currents; Dynamics; Large-scale motions; Ocean circulation.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00174/28512/26877.pdf
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The SAMBA experiment. Volume 1 : SAMBA 1 LAGRANGIAN and CTD DATA. February 1994 -August 1995 ArchiMer
Ollitrault, Michel; Auffret, Yves; Cortes, Norbert; Hemon, Catherine; Jegou, Paul; Le Reste, Serge; Loaec, Gerard; Rannou, Jean Philippe.
In February 1994, during the SAMBA 1 cruise, 9 CTD casts were done and 22 subsurface floats (20 MARVOR, 1 VCM, 1 ALFOS) launched near 800 dbar in the Brazil basin, within the framework of the SAMBA Experiment. SAMBA (SubAntartic Motions in the Brazil bAsin), is a component of the WOCE float program, and aims at describing the absolute general circulation of the Antarctic Intermediate Water around 800 m depth in the Brazil basin. MARVOR and ALFOS floats cycle every 2 months between thier nominal depth and surface to transmit data via the ARGOS system and were programmed for 30 cycles, i.e. a total life of 5 years. THE VCM float, on the other hand is a one shot RAFOS-type float which was programmed for a 1.5 year mission at depth. This report presents the...
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Ano: 1995 URL: http://archimer.ifremer.fr/doc/00238/34946/33308.pdf
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The TOPOGULF experiment lagrangian data ArchiMer
Ollitrault, Michel.
From July 1983 to June 1989, the TOPOGULF experiment took place in the North Atlantic, to investigate the large scale and mesoscale circulations in the area of the Mid-Atlantic Ridge (MAR). The TOPOGULF experiment comprised hydrographic (CTD, O2 and nutrient data) sections, long-term current meter measurements, tracking of lagrangian surlace and subsurface floats, and geochernical observations. Hydrographie and eulerian data have aIready been published (The TOPOGULF group, 1986 and 1987). This data report presents the results obtained from the 3 surface drifters and the 30 SOFAR floats launched during the TOPOGULF experiment. In early July 1983, 3 surface drifters, drogued at 100 m depth and 15 SOFAR floats ballasted for 700 dbar were launched in the...
Tipo: Text
Ano: 1994 URL: http://archimer.ifremer.fr/doc/1994/rapport-4353.pdf
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