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| Registros recuperados: 20 | |
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| Simon, Quentin; Thouveny, Nicolas; Bourles, Didier L.; Valet, Jean-pierre; Bassinot, Franck; Menabreaz, Lucie; Guillou, Valery; Choy, Sandrine; Beaufort, Luc. |
| Geomagnetic dipole moment variations associated with polarity reversals and excursions are expressed by large changes of the cosmogenic nuclide beryllium-10 (10Be) production rates. Authigenic 10Be/9Be ratios (proxy of atmospheric 10Be production) from oceanic cores therefore complete the classical information derived from relative paleointensity (RPI) records. This study presents new authigenic 10Be/9Be ratio results obtained from cores MD05-2920 and MD05-2930 collected in the west equatorial Pacific Ocean. Be ratios from cores MD05-2920, MD05-2930 and MD90-0961 have been stacked and averaged. Variations of the authigenic 10Be/9Be ratio are analyzed and compared with the geomagnetic dipole low series reported from global RPI stacks. The largest 10Be... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00358/46910/46811.pdf |
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| Jorry, Stephan J.; Droxler, Andre W.; Mallarino, Gianni; Dickens, Gerald R.; Bentley, Sam J.; Beaufort, Luc; Peterson, Larry C.; Opdyke, Bradley N.. |
| Since Last Glacial Maximum (23-19 ka), Earth climate warming and deglaciation occurred in two major steps (Bolling-Allerod and Preboreal), interrupted by a short cooling interval referred to as the Younger Dryas (12.5-11.5 ka B. P.). In this study, three cores (MV-33, MV-66, and MD-40) collected in the central part of Pandora Trough (Gulf of Papua) have been analyzed, and they reveal a detailed sedimentary pattern at millennial timescale. Siliciclastic turbidites disappeared during the Bolling-Allerod and Preboreal intervals to systematically reoccur during the Younger Dryas interval. Subsequent to the final disappearance of the siliciclastic turbidites a calciturbidite occurred during meltwater pulse 1B. The Holocene interval was characterized by a lack... |
| Tipo: Text |
Palavras-chave: Younger dryas event; Oxygen isotope records; Meltwater pulse 1a; Great barrier reef; Pacific warm pool; Carbonate platforms; Tropical atlantic; Surface salinity; Nicaragua rise; Caribbean sea. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/00079/19014/16592.pdf |
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| Bassinot, Franck; Beaufort, Luc; Vincent, Edith; Labeyrie, Laurent; Rostek, Frauke; Muller, Pj; Quidelleur, Xavier; Lancelot, Y. |
| We examined coarse fraction contents of pelagic carbonates deposited between 2000- and 3700-m water depth in the tropical Indian Ocean using ocean Drilling Program (ODP) sites 722 (Owen Ridge, Arabian Sea) and 758 (Ninetyeast Ridge, eastern equatorial Indian Ocean), and four giant piston cores collected by the French RN Marion Dufresne during the SEYMAMA expedition. Over the last 1500 kyr, coarse fraction records display high-amplitude oscillations with an irregular wavelength on the order of approximately 500 kyr. These oscillations can be correlated throughout the entire equatorial Indian Ocean, from the Seychelles area eastward to the Ninetyeast Ridge, and into the Arabian Sea. Changes in grain size mainly result from changes in carbonate dissolution as... |
| Tipo: Text |
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| Ano: 1994 |
URL: https://archimer.ifremer.fr/doc/00100/21114/37251.pdf |
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| Thevenon, Florian; Williamson, David; Bard, Edouard; Anselmetti, Flavio S.; Beaufort, Luc; Cachier, Helene. |
| This paper addresses the quantification of combustion-derived products in oceanic and continental sediments by optical and chemical approaches, and the interest of combining such methods for reconstructing past biomass burning activity and the pyrogenic carbon cycle. In such context, the dark particles >0.2 mu m(2) remaining after the partial digestion of organic matter are optically counted by automated image analysis and defined as charcoal, while the elemental carbon remaining after thermal and chemical oxidative treatments is quantified as black carbon (BC). The obtained pyrogenic carbon records from three sediment core-based case studies, (i) the Late Pleistocene equatorial Pacific Ocean. (ii) the mid-Holocene European Lake Lucerne, and (iii) the... |
| Tipo: Text |
Palavras-chave: Biomass burning; Carbon cycle; Charcoal; Black carbon; Climate; Human impact. |
| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00231/34198/32764.pdf |
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| Beaufort, Luc; Bolton, Clara T; Sarr, Anta-clarisse; Sucheras-marx, Baptiste; Rosenthal, Yair; Donnadieu, Yannick; Barbarin, Nicholas; Bova, Samantha; Cornuault, Pauline; Gally, Yves; Gray, Emmeline; Mazur, Jean-charles; Tetard, Martin. |
| The effect of global climate cycles driven by Earth’s orbital variations on evolution is poorly understood because of difficulties achieving sufficiently-resolved records of past evolution. The fossil remains of coccolithophores, a key calcifying phytoplankton group, enable an exceptional assessment of the impact of cyclic orbital-scale climate change on evolution because of their abundance in marine sediments, and because coccolithophores demonstrate extreme morphological plasticity in response to the changing environment1,2. Recently, evolutionary genetic analyses linked broad changes in Pleistocene fossil coccolith morphology to species radiation events3. Here, using high-resolution coccolith data, we show that during the last 2.8 million years... |
| Tipo: Text |
Palavras-chave: Paleoceanography; Climate cycles; Global carbon cycle; Phytoplankton evolution; Tropical seasonality. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00658/77054/78353.pdf |
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| Francis, Jason M.; Daniell, James J.; Droxler, Andre W.; Dickens, Gerald R.; Bentley, Samuel J.; Peterson, Larry C.; Opdyke, Bradley N.; Beaufort, Luc. |
| The Gulf of Papua (GoP) has become a focal point for understanding the deposition and accumulation of siliciclastic and carbonate material along and across a low-latitude continental margin. Although studies have addressed submarine geomorphological features on the inner and middle shelves, as well as processes that may have led to their formation, the seafloor of adjacent slope regions remains poorly documented. This study presents and interprets results from approximately 13,000 line-km of multibeam bathymetry, 9500 line-km of 3.5 kHz seismic, and 122 sediment cores that were collected from the GoP shelf edge and slope, primarily on two cruises (PANASH and PECTEN). Bathymetric maps, in conjunction with the seismic profiles and cores, were used to make... |
| Tipo: Text |
Palavras-chave: Great barrier reef; New Guinea; Platform margin; Foreland basin; OF Papua; Sedimentation; Shelf; Bank; Circulation; Australia. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00208/31938/30356.pdf |
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| Duchamp-alphonse, Stephanie; Siani, Giuseppe; Michel, Elisabeth; Beaufort, Luc; Gally, Yves; Jaccard, Samuel L.. |
| Several synergistic mechanisms were likely involved in the last deglacial atmospheric pCO2 rise. Leading hypotheses invoke a release of deep-ocean carbon through enhanced convection in the Southern Ocean (SO) and concomitant decreased efficiency of the global soft-tissue pump (STP). However, the temporal evolution of both the STP and the carbonate counter pump (CCP) remains unclear, thus preventing the evaluation of their contributions to the pCO2 rise. Here we present sedimentary coccolith records combined with export production reconstructions from the Subantarctic Pacific to document the leverage the SO biological carbon pump (BCP) has imposed on deglacial pCO2. Our data suggest a weakening of BCP during the phases of carbon outgassing, due in part to... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00445/55643/57288.pdf |
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| Le Mezo, Priscilla; Beaufort, Luc; Bopp, Laurent; Braconnot, Pascale; Kageyama, Masa. |
| The current-climate Indian monsoon is known to boost biological productivity in the Arabian Sea. This paradigm has been extensively used to reconstruct past monsoon variability from palaeo-proxies indicative of changes in surface productivity. Here, we test this paradigm by simulating changes in marine primary productivity for eight contrasted climates from the last glacial-interglacial cycle. We show that there is no straightforward correlation between bo-real summer productivity of the Arabian Sea and summer monsoon strength across the different simulated climates. Locally, productivity is fuelled by nutrient supply driven by Ekman dynamics. Upward transport of nutrients is modulated by a combination of alongshore wind stress intensity, which drives... |
| Tipo: Text |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00420/53146/55345.pdf |
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| Pichevin, Laetitia; Ganeshram, Raja S.; Francavilla, Stephen; Arellano-torres, Elsa; Pedersen, Tom F.; Beaufort, Luc. |
| We present new high-resolution N isotope records from the Gulf of Tehuantepec and the Nicaragua Basin spanning the last 50-70 ka. The Tehuantepec site is situated within the core of the north subtropical denitrification zone while the Nicaragua site is at the southern boundary. The delta N-15 record from Nicaragua shows an "Antarctic" timing similar to denitrification changes observed off Peru-Chile but is radically different from the northern records. We attribute this to the leakage of isotopically heavy nitrate from the South Pacific oxygen minimum zone (OMZ) into the Nicaragua Basin. The Nicaragua record leads the other eastern tropical North Pacific (ETNP) records by about 1000 years because denitrification peaks in the eastern tropical South Pacific... |
| Tipo: Text |
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| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00231/34244/32645.pdf |
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| Bolliet, Timothe; Holbourn, Ann; Kuhnt, Wolfgang; Laj, Carlo; Kissel, Catherine; Beaufort, Luc; Kienast, Markus; Andersen, Nils; Garbe-schoenberg, Dieter. |
| We present sea surface, upper thermocline, and benthic delta O-18 data, as well as temperature and paleoproductivity proxy data, from the International Marine Global Change Study Program (IMAGES) Core MD06-3067 (6 degrees 31' N, 126 degrees 30' E, 1575 m water depth), located in the western equatorial Pacific Ocean within the flow path of the Mindanao Current. Our records reveal considerable glacial-interglacial and suborbital variability in the Mindanao Dome upwelling over the last 160 kyr. Dome activity generally intensified during glacial intervals resulting in cooler thermocline waters, whereas it substantially declined during interglacials, in particular in the early Holocene and early marine oxygen isotope stage (MIS) 5e, when upwelling waters did... |
| Tipo: Text |
Palavras-chave: Mindanao Dome; East Asian monsoon; Oceanic circulation. |
| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00213/32472/30924.pdf |
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| Tripati, Aradhna K.; Sahany, Sandeep; Pittman, Dustin; Eagle, Robert A.; Neelin, J. David; Mitchell, Jonathan L.; Beaufort, Luc. |
| During the Last Glacial Maximum, tropical sea surface temperatures were 1 to 3 degrees C cooler than present(1-4), but the altitude of the snowlines of tropical glaciers(5,6) was lower than would be expected in light of these sea surface temperatures. Indeed, both glacial and twentieth-century snowlines seem to require lapse rates that are steeper than a moist adiabat(7,8). Here we use estimates of Last Glacial Maximum sea surface temperature in the Indo-Pacific warm pool based on the clumped isotope palaeotemperature proxy in planktonic foraminifera and coccoliths, along with radiative-convective calculations of vertical atmospheric thermal structure, to assess the controls on tropical glacier snowlines. Using extensive new data sets for the region, we... |
| Tipo: Text |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00290/40169/39048.pdf |
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| Tcherepanov, Evgueni N.; Droxler, Andre W.; Lapointe, Philippe; Dickens, Gerald R.; Bentley, Sam J.; Beaufort, Luc; Peterson, Larry C.; Daniell, James; Opdyke, Bradley N.. |
| This paper outlines the evolution of the late Cenozoic mixed carbonate-siliciclastic depositional system in the Gulf of Papua (GoP), using seismic, gravity, multibeam bathymetry, well data sets, and Landsat imagery. The deposition of the mixed sedimentary sequences was influenced by dynamic interplay of tectonics, eustasy, in situ carbonate production, and siliciclastic sediment supply. The roles of these major factors are estimated during different periods of the GoP margin evolution. The Cenozoic mixed system in the GoP formed in distinct phases. The first phase ( Late Cretaceous-Paleocene) was mostly driven by tectonics. Rifting created grabens and uplifted structural blocks which served later as pedestals for carbonate edifices. Active neritic... |
| Tipo: Text |
Palavras-chave: Great barrier reef; Sea level; Tectonic controls; Ice volume; Platforms; Sedimentation; Fluctuations; Deposition; Australia; Foreland basin. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00208/31939/30357.pdf |
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| Tetard, Martin; Licari, Laetitia; Beaufort, Luc. |
| The intensity of the Oxygen Minimum Zone (OMZ) of the Eastern North Pacific (ENP) experienced strong variations during the last Glacial, mirroring changes in the balance between export production (O2-consumption) and water mass ventilation (O2-renewal). In this paper we present a new benthic foraminiferal assemblages record from Core MD02-2508, recovered from the Pacific slope off Baja California, Mexico. The record reflects oxygen conditions at the northern limit of the OMZ during the last 80 kyr. We statistically identified three assemblages, characteristic of dysoxic, suboxic and oxic conditions, which we used to produce the first semi-quantitative reconstruction of [O2] for the northeastern Pacific Ocean. Our results show that the estimated [O2]... |
| Tipo: Text |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00374/48521/48797.pdf |
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| Winter, Amos; Henderiks, Jorijntje; Beaufort, Luc; Rickaby, Rosalind E. M.; Brown, Christopher W.. |
| Coccolithophores are one of the most abundant eukaryotic phytoplankton in the oceans and are distinguished by their ability to build calcitic platelets (coccoliths). Of the numerous species, Emiliania huxleyi is considered one of the major calcifiers in the pelagic ocean. There is growing concern that increasing levels of CO2 in the atmosphere and the subsequent acidification of the ocean may disrupt the production of coccoliths. Furthermore, any change in the global distribution and abundance of E. huxleyi relative to non-calcifying groups of phytoplankton (e. g. diatoms) will have important effects on the biogeochemical cycling of carbon and climatic feedbacks. We review different lines of evidence that suggest E. huxleyi is increasingly expanding its... |
| Tipo: Text |
Palavras-chave: Coccolithophores; Biogeography; Poles; Geochemical cycling. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00292/40350/38929.pdf |
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| Fraser, Nicholas; Kuhnt, Wolfgang; Holbourn, Ann; Bolliet, Timothe; Andersen, Nils; Blanz, Thomas; Beaufort, Luc. |
| Proxy records of hydrologic variability in the West Pacific Warm Pool (WPWP) have revealed wide-scale changes in past convective activity in response to orbital and suborbital climate forcings. However, attributing proxy responses to regional changes in WPWP hydrology versus local variations in precipitation requires independent records linking the terrestrial and marine realms. We present high-resolution stable isotope, U-37(K) sea surface temperature, X-ray fluorescence (XRF) core scanning, and coccolithophore-derived paleoproductivity records covering the past 120ka from International Marine Global Change (IMAGES) Program Core MD06-3075 (6 degrees 29N, 125 degrees 50E, water depth 1878m), situated in the Davao Gulf on the southern side of Mindanao.... |
| Tipo: Text |
Palavras-chave: Intertropical Convergence Zone; West Pacific Warm Pool; Walker circulation; Seawater 18O; X-ray fluorescence. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00289/40057/39357.pdf |
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| Sisavath, Emmanuelle; Mazuel, Aude; Jorry, Stephan; Babonneau, Nathalie; Bachelery, Patrick; De Voogd, Beatrice; Salpin, Marie; Emmanuel, Laurent; Beaufort, Luc; Toucanne, Samuel. |
| The present study focused on turbidite sedimentation in the Cilaos turbidite system, a volcaniclastic deep-sea fan recently recognized offshore La Réunion Island. A set of piston cores was collected in order to establish the stratigraphy of this fan and to examine the processes controlling the turbidite sedimentation off the Cilaos cirque (Piton des Neiges volcanic massif) over the last climatic cycle. Two main phases of turbidite activity were identified, during the ca 140–127 ka and 30–0 ka periods, coinciding with the two last glacial–interglacial transitions (i.e., Terminations II and I). In addition to changes in climate and eustatic sea-level, these periods coincide with a low effusive volcanic activity of the Piton des Neiges volcano. The high... |
| Tipo: Text |
Palavras-chave: Turbidites; La Reunion Island; Indian Ocean; Late Quaternary; Volcaniclastic system. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00105/21659/19383.pdf |
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| Regoli, Fabienne; De Garidel-thoron, Thibault; Tachikawa, Kazuyo; Jian, Zhiming; Ye, Liming; Droxler, Andre W.; Lenoir, Guillaume; Crucifix, Michel; Barbarin, Nicolas; Beaufort, Luc. |
| The depth of equatorial Pacific thermocline is diagnostic of the main modes of tropical climates. Past estimates of Pacific thermocline dynamics have been reconstructed either for the Last Glacial Maximum or on longer timescales at low resolution. Here we document a new high-resolution set of reconstructed past sea surface and subsurface waters temperatures from the southwestern subequatorial Pacific, core MD05-2930, in the Gulf of Papua, over the last 800 ka. We used two morphotypes of Globigerinoides ruber known to live at different water depths to reconstruct past stratification. We estimated calcification temperature of each morphotypes by Mg/Ca paleothermometry. Our subequatorial Pacific thermocline paleotemperature record indicates a response of the... |
| Tipo: Text |
Palavras-chave: Equatorial Pacific; Thermocline; Pleistocene. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00295/40572/39477.pdf |
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| Registros recuperados: 20 | |
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