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Registros recuperados: 53
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Evidence of strong inertia-gravity wave activity during the POMME experiment ArchiMer
Bouruet-aubertot, Pascale; Mercier, Herle; Gaillard, Fabienne; Lherminier, Pascale.
The purpose of this paper is to characterize inertia-gravity waves (IGW) activity and to investigate the variability of these waves in relationship to atmospheric forcing and larger-scale motions. To this aim, we analyzed Eulerian measurements of horizontal currents and temperature collected over 1 year during the Programme Océan Multidisciplinaire Méso Echelle (POMME). We focused on the main frequency components of the IGW spectrum, namely the inertial frequency f and the semidiurnal frequency M2. Time evolution of the relative energy of these two components gave evidence of isolated events of high intensity. We performed a detailed analysis of these events and identified mechanisms of generation of these waves. Localized spots of intense, near-inertial...
Tipo: Text Palavras-chave: Turbulent mixing; Tnertia gravity waves.
Ano: 2005 URL: http://archimer.ifremer.fr/doc/2005/publication-359.pdf
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Internal and forced variability along a section between Greenland and Portugal in the CLIPPER Atlantic model ArchiMer
Treguier, Anne-marie; Gourcuff, Claire; Lherminier, Pascale; Mercier, Herle; Barnier, Bernard; Madec, Gurvan; Molines, Jean-marc; Penduff, Thierry; Czeschel, Lars; Boning, Claus.
Numerical models are used to estimate the meridional overturning and transports along the paths of two hydrographic cruises, carried out in 1997 and 2002 from Greenland to Portugal. We have examined the influence of the different paths of the two cruises and found that it could explain 0.4 to 2 Sv of difference in overturning (the precise value is model-dependent). Models show a decrease in the overturning circulation between 1997 and 2002, with different amplitudes. The CLIPPER ATL6 model reproduces well the observed weakening of the overturning in density coordinates between the cruises; in the model, the change is due to the combination of interannual and high-frequency forcing and internal variability associated with eddies and meanders. Examination of...
Tipo: Text Palavras-chave: Ocean model; Thermohaline circulation; North Atlantic; Climate variability; Oceanography.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2199.pdf
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Transports across the 2002 Greenland-Portugal Ovide section and comparison with 1997 - art. no. C07003 ArchiMer
Lherminier, Pascale; Mercier, Herle; Gourcuff, Claire; Alvarez, M; Bacon, S; Kermabon, Catherine.
The first Ovide cruise occurred in June-July 2002 on R/V Thalassa between Greenland and Portugal. The absolute transports across the Ovide line are estimated using a box inverse model constrained by direct acoustic Doppler current profiler velocity measurements and by an overall mass balance (+/-3 Sv, where 1 Sv = 10(6) m(3) s(-1)) across the section. Main currents are studied and compared to the results of the similar Fourex section performed in August 1997 and revisited here. The meridional overturning cell (MOC) is estimated in two different ways, both leading to a significantly lower value in June 2002 than in August 1997, consistent with the relative strength of the main components of the MOC (North Atlantic Current and deep western boundary current)....
Tipo: Text Palavras-chave: Hydrographic section; Cell; Meridional overturning; North Atlantic circulation.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3296.pdf
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North Atlantic Ocean circulation: the OVIDE project ArchiMer
Mercier, Herle; Lherminier, Pascale; Gourcuff, Claire.
The OVIDE project studies the variability of the north Atlantic subbpolar gyre circulation based on repeated hydrography and current measurements, satellite observations, diagnostic and prognostic models. Here, we present an analysis of volume and heat transports between Greenland and Portugal from the 2002 OVIDE data. The results are compared to a previous analysis based on 1997 data (4x project). We focus on the thermohaline circulation. The thermohaline circulation, deep western boundary current and heat flux variability are correlated.
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Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-6102.pdf
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Recent changes in the Greenland-Scotland overflow-derived water transport inferred from hydrographic observations in the southern Irminger Sea ArchiMer
Sarafanov, Artem; Falina, Anastasia; Mercier, Herle; Lherminier, Pascale; Sokov, Alexey.
Recent decadal changes (1955-2007) in the baroclinic transport (TBC) of the Deep Western Boundary Current (DWBC) carrying the Greenland-Scotland overflow-derived waters along the East Greenland slope are quantified from a set of hydrographic sections in vicinity of Cape Farewell. The updated historical record of TBC shows clear decadal variability (+/- 2-2.5 Sv) with the transport minima in the 1950s and mid-1990s, maximum in the early 1980s and moderate-to-high transport in the 2000s. Since the mid-1990s, the DWBC TBC has increased by similar to 2 Sv (significant at the 99.9% level), which constitute similar to 20% of the mean absolute transport (9.0 Sv) as obtained from three cruises in 2002-2006. The DWBC TBC anomalies negatively correlate (R = -0.80)...
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Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6633.pdf
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OVIDE : Rapport de données Eulériennes ArchiMer
Branellec, Pierre; Lherminier, Pascale.
Complementing the study of the variability of the North Atlantic Subpolar Gyre that is performed in the frame of the Ovide project, the East Greenland/Irminger Current (EGIC) was measured at 60°N between June 2004 to June 2006 by an array of 5 moorings, placed on a section from the shelf to the 1900m isobath. The moorings were equipped with 15 RCM currentmeters and 2 ADCPs to measure the volume transport, and also 5 micro-CTD at mooring heads (about 200m below the surface) to measure the vertical displacement of the moorings and the variability of the warm and salty water masses in the Irminger Current. The highest velocities, about 80 cm/s, are found at the top of mooring B. The core of the current is located between moorings B and C. The current...
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Ano: 2009 URL: http://archimer.ifremer.fr/doc/00211/32202/30638.pdf
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XBT Temperature Errors during French Research Cruises (1999-2007) ArchiMer
Reverdin, Gilles; Marin, Frederic; Bourles, Bernard; Lherminier, Pascale.
Data from French cruises in 1999-2007, a period during which Deep Blue (DB) or T7 expendable bathythermographs (XBTs) were deployed, and for which ancillary temperature data are available in the northeast Atlantic and equatorial Atlantic regions, are examined. There was a total of 16 cruises with XBTs launched between conductivity-temperature-depth (CTD) stations; during most of these, as well as during three additional cruises that were also considered, intake temperature was measured. XBT data from two voluntary observing ships in the North Atlantic subpolar gyre for which intake temperature was measured were also investigated. There is an XBT cold bias due to stirring of a stratified upper layer by the ship, resulting in differences between XBT...
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Ano: 2009 URL: http://archimer.ifremer.fr/doc/00133/24380/22391.pdf
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A Long-Lasting Mode Water Vortex in the Northeast Atlantic Ocean ArchiMer
Reverdin, Gilles; Gascard, Jean-claude; Le Cann, Bernard; Prieur, Loic; Assenbaum, Michel; Lherminier, Pascale.
An anticyclonic mode water vortex and its environment were investigated from November 2000 to September 2001 in the northeast Atlantic (near 43.5 degrees N, 15 degrees-19 degrees W) with neutrally buoyant drifting floats, moored current meters, satellite altimetric sea surface height, and several hydrological surveys and sections. These observations reveal a coherent inner core (similar to 0 km in diameter) made of very oxygenated northeast Atlantic central waters (11 degrees-12.7 degrees C and 35.5-35.7 on the 1978 practical salinity scale) from 150 m down to about 750-m depth. The core presents high relative vorticity (up to approximately -0.5 times the Coriolis frequency f) within at least 10 km of its center, near 400-700 m. Peak velocity along the...
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Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6357.pdf
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Campagne OVIDE 2006 : Rapport de données CTD-O2 ArchiMer
Branellec, Pierre; Lherminier, Pascale.
Le projet Ovide, sous la direction d'Herlé Mercier, a pour objectif d'établir un observatoire de la variabilité de la circulation dans l'océan Atlantique Nord. Le projet s'articule principalement autour de la répétition tous les deux ans d'une section hydrologique de Cap Hoppe au sud-est du Groenland à Cap Mendocino au Portugal, répertoriée sous le nom de A25 dans le programme international CLIVAR (Climate Variability). Elle traverse la Mer d'Irminger, la dorsale de Reykjanes, le Bassin d'Islande, le Bassin Ouest Européen (au sud du plateau de Rockall) et la Plaine Abyssale Ibérique, perpendiculairement aux courants principaux. La répétition de campagnes le long de ce trajet tous les deux ans pendant une période de dix ans permet de documenter l'évolution...
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Ano: 2009 URL: http://archimer.ifremer.fr/doc/00210/32103/30560.pdf
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Assessing decadal changes in the Deep Western Boundary Current absolute transport southeast of Cape Farewell, Greenland, from hydrography and altimetry ArchiMer
Sarafanov, Artem; Falina, Anastasia; Lherminier, Pascale; Mercier, Herle; Sokov, Alexey; Gourcuff, Claire.
[1] In earlier studies, the decadal variability of the Deep Western Boundary Current (DWBC) transport in the vicinity of Cape Farewell, Greenland, has been assessed from changes in the baroclinic velocities computed from hydrographic data and referenced to 1000 m depth. The main limitation of using such an estimate as an index for the DWBC absolute transport variability comes from the unaccounted for decadal velocity changes at the reference level (1000 m). These changes may substantially contribute to the DWBC absolute transport variability by compensating for or adding to the baroclinic transport changes. To assess this contribution to variability, we quantify the decadal velocity changes which occurred at 1000 m depth southeast of Cape Farewell since...
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00017/12855/9820.pdf
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Trends of anthropogenic CO2 storage in North Atlantic water masses ArchiMer
Perez, F. F; Vazquez-rodriguez, M.; Mercier, Herle; Velo, A.; Lherminier, Pascale; Rios, A. F..
A high-quality inorganic carbon system database, spanning over three decades (1981-2006) and comprising of 13 cruises, has allowed the applying of the phi C degrees(T) method and coming up with estimates of the anthropogenic CO2 (C-ant) stored in the main water masses of the North Atlantic. In the studied region, strong convective processes convey surface properties, like C-ant, into deeper ocean layers and grants this region an added oceanographic interest from the point of view of air-sea CO2 exchanges. Generally, a tendency for decreasing C-ant storage rates towards the deep layers has been observed. In the Iberian Basin, the North Atlantic Deep Water has low C-ant concentrations and negligible storage rates, while the North Atlantic Central Water in...
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00006/11706/8362.pdf
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The Atlantic Meridional Overturning Circulation and the subpolar gyre observed at the A25-OVIDE section in June 2002 and 2004 ArchiMer
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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Cessation and partial reversal of deep water freshening in the northern North Atlantic: observation-based estimates and attribution ArchiMer
Sarafanov, Artem; Mercier, Herle; Falina, Anastasia; Sokov, Alexey; Lherminier, Pascale.
Recent decadal salinity changes in the Greenland-Scotland overflow-derived deep waters are quantified using CTD data from repeated hydrographic sections in the Irminger Sea. The Denmark Strait Overflow Water salinity record shows the absence of any net change over the 1980s-2000s; changes in the Iceland-Scotland Overflow Water (ISOW) and in the deep water column (Sigma(0) > 27.82), enclosing both overflows, show a distinct freshening reversal in the early 2000s. The observed freshening reversal is a lagged consequence of the persistent ISOW salinification that occurred upstream, in the Iceland Basin, after 1996 in response to salinification of the northeast Atlantic waters entrained into the overflow. The entrainment salinity increase is explained by...
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/2010/publication-7325.pdf
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Altimetry combined with hydrography for ocean transport estimation ArchiMer
Gourcuff, Claire; Lherminier, Pascale; Mercier, Herle; Le Traon, Pierre-yves.
A method to estimate mass and heat transports across hydrographic sections using hydrography together with altimetry data in a geostrophic box inverse model is presented. Absolute surface velocities computed from AVISO altimetry products made up of a combination of sea surface height measurements and geoid estimate are first compared to Ship Acoustic Doppler Current Profiler (S-ADCP) measurements of the Ovide project along hydrographic sections repeated every 2 years in summer from Portugal to Greenland. The rms difference between S-ADCP and altimetry velocities averaged on distances of about a hundred km accounts to 3.3 cm s−1. Considering that the uncertainty of S-ADCP velocities is found at 1.5 cm s−1, altimetry errors are estimated at 3 cm s−1....
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00038/14921/13751.pdf
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The 1992-2009 transport variability of the East Greenland-Irminger Current at 60 degrees N ArchiMer
Daniault, N.; Mercier, Herle; Lherminier, Pascale.
The East Greenland Irminger Current (EGIC) decadal transport variability likely influences deep convection intensity in the Labrador and Irminger Seas but is poorly known yet. The EGIC transport west of the 2000 m isobath was estimated, for the first time, between 1992 and 2009 by combining surface geostrophic velocities derived from altimetry with an estimate of the vertical structure of the transport variability statistically determined from a moored array deployed in 2004-2006. The reconstructed 17-year time series of the EGIC transport was then validated against independent estimates confirming that, indeed, the vertical distribution of the EGIC variability has not changed significantly over the last two decades. The 1992-2009 mean transport is 19.5 Sv...
Tipo: Text Palavras-chave: Keywords: East Greenland Current; Irminger Current; Transport variability.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00033/14467/11763.pdf
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Campagne OVIDE 2008 : Rapport de données CTD-O2 ArchiMer
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...
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00210/32124/30568.pdf
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CASCADE V6.1 : Logiciel de validation et de visualisation des mesures ADCP de coque ArchiMer
Le Bot, Philippe; Kermabon, Catherine; Lherminier, Pascale; Gaillard, Fabienne.
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00342/45285/44750.pdf
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On the Cascading of Dense Shelf Waters in the Irminger Sea ArchiMer
Falina, Anastasia; Sarafanov, Artem; Mercier, Herle; Lherminier, Pascale; Sokov, Alexey; Daniault, Nathalie.
Hydrographic data collected in the Irminger Sea in the 1990s-2000s indicate that dense shelf waters carried by the East Greenland Current south of the Denmark Strait intermittently descend (cascade) down the continental slope and merge with the deep waters originating from the Nordic Seas overflows. Repeat measurements on the East Greenland shelf at similar to 200 km south of the Denmark Strait (65 degrees-66 degrees N) reveal that East Greenland shelf waters in the Irminger Sea are occasionally as dense (sigma(0) > 27.80) as the overflow-derived deep waters carried by the Deep Western Boundary Current (DWBC). Clear hydrographic traces of upstream cascading of dense shelf waters are found over the continental slope at 64.3 degrees N, where the densest...
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Ano: 2012 URL: http://archimer.ifremer.fr/doc/00130/24160/22255.pdf
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Mean full-depth summer circulation and transports at the northern periphery of the Atlantic Ocean in the 2000s ArchiMer
Sarafanov, Artem; Falina, Anastasia; Mercier, Herle; Sokov, Alexey; Lherminier, Pascale; Gourcuff, Claire; Gladyshev, Sergey; Gaillard, Fabienne; Daniault, Nathalie.
A mean state of the full-depth summer circulation in the Atlantic Ocean in the region in between Cape Farewell (Greenland), Scotland and the Greenland-Scotland Ridge (GSR) is assessed by combining 2002–2008 yearly hydrographic measurements at 59.5°N, mean dynamic topography, satellite altimetry data and available estimates of the Atlantic–Nordic Seas exchange. The mean absolute transports by the upper-ocean, mid-depth and deep currents and the Meridional Overturning Circulation (MOCσ = 16.5 ± 2.2 Sv, at σ0 = 27.55) at 59.5°N are quantified in the density space. Inter-basin and diapycnal volume fluxes in between the 59.5°N section and the GSR are then estimated from a box model. The dominant components of the meridional exchange across 59.5°N are the North...
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Ano: 2012 URL: http://archimer.ifremer.fr/doc/00059/16997/14499.pdf
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Atlantic Ocean CO2 uptake reduced by weakening of the meridional overturning circulation ArchiMer
Perez, Fiz F.; Mercier, Herle; Vazquez-rodriguez, Marcos; Lherminier, Pascale; Velo, Anton; Pardo, Paula C.; Roson, Gabriel; Rios, Aida F..
Uptake of atmospheric carbon dioxide in the subpolar North Atlantic Ocean declined rapidly between 1990 and 2006. This reduction in carbon dioxide uptake was related to warming at the sea surface, which-according to model simulations-coincided with a reduction in the Atlantic meridional overturning circulation. The extent to which the slowdown of this circulation system-which transports warm surface waters to the northern high latitudes, and cool deep waters south-contributed to the reduction in carbon uptake has remained uncertain. Here, we use data on the oceanic transport of volume, heat and carbon dioxide to track carbon dioxide uptake in the subtropical and subpolar regions of the North Atlantic Ocean over the past two decades. We separate...
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Ano: 2013 URL: https://archimer.ifremer.fr/doc/00135/24625/22712.pdf
Registros recuperados: 53
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