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| Registros recuperados: 38 | |
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| 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° (latitude) by 4° (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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| Palm, Franziska A.; Peakall, Jeff; Hodgson, David M.; Marsset, Tania; Silva Jacinto, Ricardo; Dennielou, Bernard; Babonneau, Nathalie; Wright, Tim J.. |
| Submarine-fan channels can build the largest sediment accumulations on Earth, but our understanding of flow and sedimentation processes related to channel evolution remains limited. Results from physical and numerical modelling predict dominantly downstream channel bend migration. However, observations and evolutionary models for aggradational submarine channels on passive margins suggest that bends are dominated by lateral expansion. This paradox may be due to limitations induced by the use of constant width channels in process studies. Constant width has been used for two reasons: partly because this is the simplest possible case, but primarily because the width variation around submarine channel bends is unknown. Channel width variations are examined... |
| Tipo: Text |
Palavras-chave: Submarine channel; Congo; Channel morphology; Sedimentation; Bank pull; Quaternary; Monsoon; South Atlantic. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00693/80473/83602.pdf |
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| Gioia, Rosalinda; Macleod, Matthew; Castro-jimenez, Javier; Nizzetto, Luca; Dachs, Jordi; Lohmann, Rainer; Jones, Kevin C.. |
| A diel (24-h) cycle with daytime atmospheric concentrations higher than nighttime concentrations by a factor of 1.5-3 was observed for several low molecular weight polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in remote areas of the tropical South Atlantic during a cruise in October-November 2005. In contrast, high molecular weight PCBs and PAHs did not display diurnal variability. A model which has successfully explained diel variability of persistent organic pollutants (POPs) over land could not reproduce the observed diel cycle by considering variability in temperature, atmospheric OH radical concentrations, atmospheric boundary layer height and wind speed as causal factors. We used the model to conduct two bounding... |
| Tipo: Text |
Palavras-chave: Persistent organic pollutants (POPs); Diurnal cycle; Polychlorinated biphenyls (PCBs); Polycyclic aromatic hydrocarbons (PAHs); South Atlantic. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00645/75721/76676.pdf |
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| Mercier, Herle; Arhan, Michel; Lutjeharms, Johann. |
| The upper-layer circulation in the eastern basin of the South Atlantic was studied from hydrographic and direct velocity measurements along WOCE lines A11, A13 and A14. A13 and A14 provide quasi-meridional samplings of the equatorial, subequatorial and subtropical circulation regimes. A13 was carried out along the African coast at about 600 km offshore from it, and A 14 along the nominal longitude 9degreesW. A11 intersects the Cape Basin between 46degreesS in the west and 30degreesS in the east. Transport estimates were derived from direct velocity measurements and a box inverse model. In the equatorial eastern Atlantic, the Equatorial Undercurrent (EUC) transport decreases from 25x10(6) m(3) s(-1) at 9degreesW to 13x10(6) m(3) s(-1) at 5degreesE.... |
| Tipo: Text |
Palavras-chave: Hydrography; Current; Circulation; South Atlantic; Equatorial Atlantic. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/2003/publication-460.pdf |
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| Ansorge, Isabelle J.; Baringer, Molly; Campos, Edmo J.d.; Dong, S.; Fine, R.a.; Garzoli, Silvia L.; Goni, Gustavo; Meinen, Christopher S.; Perez, R.c.; Piola, Alberto R.; Roberts, M.j.; Speich, Sabrina; Sprintall, J.; Terre Terrillon, Thierry; Van Den Berg, M.a.. |
| The meridional overturning circulation (MOC) is a global system of surface, intermediate, and deep ocean currents. The MOC connects the surface layer of the ocean and the atmosphere with the huge reservoir of the deep sea and is the primary mechanism for transporting heat, freshwater, and carbon between ocean basins. Climate models show that past changes in the strength of the MOC were linked to historical climate variations. Further research suggests that the MOC will continue to modulate climate change scenarios on time scales ranging from decades to centuries [Latif et al., 2006]. |
| Tipo: Text |
Palavras-chave: South Atlantic; Meridional Overturning Circulation; CPIES. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00175/28609/27109.pdf |
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| Roberts, Jenny; Gottschalk, Julia; Skinner, Luke C.; Peck, Victoria L.; Kender, Sev; Elderfield, Henry; Waelbroeck, Claire; Riveiros, Natalia Vazquez; Hodell, David A.. |
| Explanations of the glacial-interglacial variations in atmospheric pCO(2) invoke a significant role for the deep ocean in the storage of CO2. Deep-ocean density stratification has been proposed as a mechanism to promote the storage of CO2 in the deep ocean during glacial times. A wealth of proxy data supports the presence of a "chemical divide" between intermediate and deep water in the glacial Atlantic Ocean, which indirectly points to an increase in deep-ocean density stratification. However, direct observational evidence of changes in the primary controls of ocean density stratification, i.e., temperature and salinity, remain scarce. Here, we use Mg/Ca-derived seawater temperature and salinity estimates determined from temperature-corrected delta O-18... |
| Tipo: Text |
Palavras-chave: South Atlantic; Density gradient; Ocean stratification; Last deglaciation; Atmospheric CO2. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53276/54569.pdf |
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| Rabouille, C.; Dennielou, Bernard; Baudin, F.; Raimonet, M.; Droz, Laurence; Khripounoff, Alexis; Martinez, P.; Mejanelle, L.; Michalopoulos, P.; Pastor, Lucie; Pruski, A.; Ragueneau, Olivier; Reyss, J.-l.; Ruffine, Livio; Schnyder, J.; Stetten, E.; Taillefert, M.; Tourolle, Julie; Olu, Karine. |
| Carbon and silicon cycles at the Earth surface are linked to long-term variations of atmospheric CO2 and oceanic primary production. In these cycles, the river-sea interface is considered a biogeochemical hotspot, and deltas presently receive and preserve a major fraction of riverine particles in shallow water sediments. In contrast, periods of glacial maximum lowstand were characterized by massive exports of sediments to the deep-sea via submarine canyons and accumulation in deep-sea fans. Here, we calculate present-day mass balances for organic carbon (OC) and amorphous silica (aSi) in the terminal lobe complex of the Congo River deep-sea fan as an analogue for glacial periods. We show that this lobe complex constitutes a megasink with the current... |
| Tipo: Text |
Palavras-chave: Present; Paleoceanography; South Atlantic; Inorganic geochemistry; Organic geochemistry; Sedimentology-marine cores. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00511/62289/66720.pdf |
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| Abadie, Cyril; Lacan, Francois; Radic, Amandine; Pradoux, Catherine; Poitrasson, Franck. |
| As an essential micronutrient, iron plays a key role in oceanic biogeochemistry. It is therefore linked to the global carbon cycle and climate. Here, we report a dissolved iron (DFe) isotope section in the South Atlantic and Southern Ocean. Throughout the section, a striking DFe isotope minimum (light iron) is observed at intermediate depths (200–1,300 m), contrasting with heavier isotopic composition in deep waters. This unambiguously demonstrates distinct DFe sources and processes dominating the iron cycle in the intermediate and deep layers, a feature impossible to see with only iron concentration data largely used thus far in chemical oceanography. At intermediate depths, the data suggest that the dominant DFe sources are linked to organic matter... |
| Tipo: Text |
Palavras-chave: Iron isotopes; GEOTRACES; South Atlantic; Southern Ocean; Remineralization. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00367/47864/47859.pdf |
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| Brea, Samenta; Alvarez Salgado, X; Alvarez, M; Perez, F; Memery, L; Mercier, Herle; Messias, M.j.. |
| The physical and biogeochemical components of nutrients and inorganic carbon distributions along WOCE line A14 are objectively separated by means of a constrained least-squares regression analysis of the mixing of eastern South Atlantic water masses. Contrary to previous approaches, essentially devoted to the intricate South Atlantic circulation, this work is focused on the effects of circulation on nutrients and carbon biogeochemistry, with special emphasis on the stoichiometry and the rate of mineralization processes. Combination of nutrient and apparent CFC-age anomalies, derived from the mixing analysis, indicate faster mineralization rates in the equatorial (12 x 10(-2) mumol P kg(-1) yr(-1)) and subequatorial (5.3 x 10(-2) mumol P kg(-1) yr(-1)) than... |
| Tipo: Text |
Palavras-chave: South Atlantic; Biogeochemical cycles; Water masses. |
| Ano: 2004 |
URL: https://archimer.ifremer.fr/doc/2004/publication-836.pdf |
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| Wefing, Anne-marie; Arps, Jennifer; Blaser, Patrick; Wienberg, Claudia; Hebbeln, Dierk; Frank, Norbert. |
| High-precision U-series dating of scleractinian cold-water corals is a key chronological tool for studies of past environmental and climate conditions. Here, we tested and optimized an automated chemical extraction system (ESI prepFAST-MC equipped with an Eichrom TRU-resin chromatographic column) for its ability to purify U and Th isotopes for mass spectrometric U-series dating at the sub-‰ precision level. Chemical yields are constantly high, on average around 90% for both U and Th. Analytical blanks are comparable to manual purification (< 0.15 pg U, 0.15 pg Th for a typical sample of 50 mg) and memory effects due to the recycling of the column are mostly insignificant as the carry-over fraction is about 10− 5 for Th and 10− 3 for U isotopes. However,... |
| Tipo: Text |
Palavras-chave: U-series dating; PrepFAST-MC; Cold-water corals; South Atlantic; Angola; Past climate. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00409/52058/52761.pdf |
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| Meinen, Christopher S.; Speich, Sabrina; Piola, Alberto R.; Ansorge, Isabelle; Campos, Edmo; Kersale, Marion; Terre Terrillon, Thierry; Chidichimo, Maria Paz; Lamont, Tarron; Sato, Olga T.; Perez, Renellys C.; Valla, Daniel; Van Den Berg, Marcel; Le Henaff, Matthieu; Dong, Shenfu; Garzoli, Silvia L.. |
| Six years of simultaneous moored observations near the western and eastern boundaries of the South Atlantic are combined with satellite winds to produce a daily time series of the basin-wide meridional overturning circulation (MOC) volume transport at 34.5 degrees S. The results demonstrate that barotropic and baroclinic signals at both boundaries cause significant transport variations, and as such must be concurrently observed. The data, spanning similar to 20 months during 2009-2010 and similar to 4 years during 2013-2017, reveal a highly energetic MOC record with a temporal standard deviation of 8.3 Sv, and strong variations at time scales ranging from a few days to years (peak-to-peak range = 54.6 Sv). Seasonal transport variations are found to have... |
| Tipo: Text |
Palavras-chave: Meridional overturning circulation; South Atlantic; Overturning; Volume transport; Observations. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00445/55612/57253.pdf |
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| Bayon, Germain; German, Cr; Nesbitt, Rw; Bertrand, P; Schneider, Rr. |
| [1] Analysis of radiogenic isotopes in marine sediments can provide useful information on the provenance and transport of detrital material, directly relevant to paleoceanographic investigations. Here we show that the detrital Nd isotopic composition of recent SE Atlantic marine sediments matches the complex modern-day hydrography. In these same cores, glacial-interglacial isotopic variations are consistent with previous investigations (using different paleoceanographic proxies), which have shown that the relative influence of North Atlantic Deep Water (NADW) into the South Atlantic was reduced during glacial periods. In a novel departure, however, we also calculate the mass accumulation rates of terrigenous material delivered by each of Circumpolar Deep... |
| Tipo: Text |
Palavras-chave: Neodymium isotopes; Detrital fractions; South Atlantic; Deep water circulation; IMAGES; Marine geology and geophysics : marine sediments processes and transport; Oceanography : general : paleoceanography. |
| Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/00000/10190/9912.pdf |
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| Cortese, G; Abelmann, A; Gersonde, R. |
| ODP Site 1089 is optimally located in order to monitor the occurrence of maxima in Agulhas heat and salt spillage from the Indian to the Atlantic Ocean. Radiolarian-based paleotemperature transfer functions allowed to reconstruct the climatic history for the last 450 kyr at this location. A warm sea surface temperature anomaly during Marine Isotope Stage (MIS) 10 was recognized and traced to other oceanic records along the surface branch of the global thermolialine (THC) circulation system, and is particularly marked at locations where a strong interaction between oceanic and atmospheric overturning cells and fronts occurs. This anomaly is absent in the Vostok ice core deuterium, and in oceanic records from the Antarctic Zone. However, it is present in the... |
| Tipo: Text |
Palavras-chave: Agulhas; Paleotemperature; Radiolarians; South Atlantic. |
| Ano: 2004 |
URL: https://archimer.ifremer.fr/doc/00229/34028/32422.pdf |
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| Meinen, Christopher S.; Speich, Sabrina; Perez, Renellys C.; Dong, Shenfu; Piola, Alberto R.; Garzoli, Silvia L.; Gladyshev, Sergey; Baringer, Molly; Campos, Edmo J. D.. |
| Data from two boundary arrays deployed along 34.5°S are combined to produce the first continuous in situ time series observations of the basin-wide meridional overturning circulation (MOC) in the South Atlantic. Daily estimates of the MOC between March 2009 and December 2010 range between 3 Sv and 39 Sv (1 Sv = 106 m3 s−1) after a 10 day low-pass filter is applied. Much of the variability in this ∼20 month record occurs at periods shorter than 100 days. Approximately two-thirds of the MOC variability is due to changes in the geostrophic (baroclinic plus barotropic) volume transport, with the remainder associated with the direct wind-forced Ekman transport. When low-pass filtered to match previously published analyses in the North Atlantic, the observed... |
| Tipo: Text |
Palavras-chave: Meridional overturning circulation; Transport; South Atlantic; Inverted echo sounder; Bottom pressure. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00167/27789/25982.pdf |
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| Boltovskoy, D; Correa, N; Boltovskoy, A. |
| Approximately 7000 marine zooplanktonic species have been described so far for the World Ocean; in the South Atlantic the presence of 40% of these has been confirmed, and an additional 20-30% are expected to be recorded in the future. The overall number of described species is very low when compared with other communities, and yet it may not be too far from the final, complete inventory. Very ample geographic distributional ranges, compositional similarity between the major oceanic basins, and declining species description rates suggest that the undescribed fraction of marine zooplankton is nowhere as large as those suggested for the biosphere as a whole. It is anticipated that the highest proportions of new species will be among the groups associated.... |
| Tipo: Text |
Palavras-chave: Zooplancton; Diversité; Atlantique Sud; Zooplancton; Diversity; South Atlantic. |
| Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/00322/43310/42964.pdf |
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| Chang, Yp; Chang, Cc; Wang, Lw; Chen, Mt; Wang, Ch; Yu, Ef. |
| A high-resolution (similar to 4 - 5cm/kyr) giant piston core record (MD962085) retrieved during an IMAGES II - NAUSICAA cruise from the continental slope of the southeast Atlantic Ocean reveal striking variations in planktonic foraminifer faunal abundances and sea-surface temperatures (SST) during the past 400,000 years. The location and high-quality sedimentary record of the core provide a good opportunity to assess changes in the intensity and position of the Benguela Current System and the Subtropical Convergence, two key features of the ocean-climate system in the south Atlantic. This record can be also used to evaluate the possible influence of Agulhas Current from the throughflow of the Indian Ocean into the South Atlantic. The planktonic foraminifer... |
| Tipo: Text |
Palavras-chave: Paleoceanography; Late Quaternary; Micropaleontology; South Atlantic. |
| Ano: 1999 |
URL: https://archimer.ifremer.fr/doc/00239/35070/34563.pdf |
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| Registros recuperados: 38 | |
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