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| Registros recuperados: 11 | |
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| Menot, Guillemette; Bard, Edouard. |
| Climatic models simulate abrupt oscillations that are associated, in the North Atlantic, with Dansgaard-Oeschger and Heinrich events. However, the geographic extension of temperature anomalies is largely uncontrolled due to the scarcity of quantitative records of sufficient time resolution on the European continent. Here, we propose, based on a recently developed temperature proxy (TEX86), a reconstruction of millennial-scale temperature variations in a Black Sea sediment archive for the last 40,000 years. Prior to any paleoclimatological interpretations the effects of potential bias, such as seasonality and depth of maximum export production on temperature reconstructions, are considered for the Black Sea. Based on previous work, a tentative method for... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00140/25124/23232.pdf |
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| Soulet, Guillaume; Menot, Guillemette; Bayon, Germain; Rostek, Frauke; Ponzevera, Emmanuel; Toucanne, Samuel; Lericolais, Gilles; Bard, Edouard. |
| Continental ice sheets are a key component of the Earth’s climate system, but their internal dynamics need to be further studied. Since the last deglaciation, the northern Eurasian Fennoscandian Ice Sheet (FIS) has been connected to the Black Sea (BS) watershed, making this basin a suitable location to investigate former ice-sheet dynamics. Here, from a core retrieved in the BS, we combine the use of neodymium isotopes, high-resolution elemental analysis, and biomarkers to trace changes in sediment provenance and river runoff. We reveal cyclic releases of meltwater originating from Lake Disna, a proglacial lake linked to the FIS during Heinrich Stadial 1. Regional interactions within the climate–lake–FIS system, linked to changes in the availability of... |
| Tipo: Text |
Palavras-chave: Ice dynamics; Meltwater routing; European hydrographic network. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00134/24489/22516.pdf |
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| Soulet, Guillaume; Menot, Guillemette; Garreta, Vincent; Rostek, Frauke; Zaragosi, Sebastien; Lericolais, Gilles; Bard, Edouard. |
| Chronologies of sediments that document the last glacial history of the Black Sea "Lake" are hampered by issues relating to reservoir age. Regulated by basin hydrology, reservoir ages represent a tool that could potentially be used to better understand the response of Black Sea "Lake" hydrology to climate change. Therefore, deciphering reservoir age evolution is crucial both for better constraining the basin chronological framework and for providing new insights into our understanding of Black Sea "Lake" hydrology. By tuning a meaningful new high-resolution geochemical dataset (obtained from core MD04-2790) to a climate reference record, here, we propose a reliable chronology spanning the last 32 kyr BP. The chronology is compared to a large AMS... |
| Tipo: Text |
Palavras-chave: Black Sea; Reservoir age; Radiocarbon; Last Glacial; Last Deglaciation; Paleoclimate. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00043/15379/12817.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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| Pichevin, Laetitia; Bard, Edouard; Martinez, Philippe; Billy, Isabelle. |
| Modern seawater profiles of oxygen, nitrate deficit, and nitrogen isotopes reveal the spatial decoupling of summer monsoon-related productivity and denitrification maxima in the Arabian Sea (AS) and raise the possibility that winter monsoon and/or ventilation play a crucial role in modulating denitrification in the northeastern AS, both today and through the past. A new high-resolution 50-ka record of delta(15) N from the Pakistan margin is compared to five other denitrification records distributed across the AS. This regional comparison unveils the persistence of east-west heterogeneities in denitrification intensity across millennial-scale climate shifts and throughout the Holocene. The oxygen minimum zone (OMZ) experienced east-west swings across... |
| Tipo: Text |
Palavras-chave: Marine N cycle; Abrupt climate changes; Arabian Sea. |
| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00233/34461/32865.pdf |
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| Cartapanis, Olivier; Tachikawa, Kazuyo; Bard, Edouard. |
| During the last glacial period, the Oxygen Minimum Zone (OMZ) within the northeastern Pacific Ocean strengthened and weakened on a millennial time scale, demonstrating a tight linkage with northern high latitude climate, although the precise mechanisms responsible remain unknown. Core MD02-2508, retrieved off Baja California, was analyzed for major and trace elements (Br, Ca, Ti, Fe, Mn, and Sr) using a XRF scanner and redox-sensitive trace elements (Cu, Ni, Cd, As, V, Cr, Mo, and U) using the ICP-MS. The trace element content, the Fe/Ti ratio, and Br-based organic carbon exhibit higher values during the Holocene and during warm Dansgaard-Oeschger events than during the Last Glacial Maximum (LGM), stadials, and Heinrich (H) events. A principal component... |
| Tipo: Text |
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| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00227/33799/32550.pdf |
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| Bard, Edouard; Heaton, Timothy J. |
| As an extended comment on the paper by Sarnthein et al. (2020), we express strong reservations about the methodology of the so-called 14C plateau tuning (PT) technique used to date marine sediment records and its implications on the determination of 14C marine reservoir ages (MRA). The main problems are linked to: the assumption of constant MRA during 14C-age plateaus; the lack of consideration of foraminifera abundance changes coupled to bioturbation that can create spurious plateaus in marine sediments; the assumption that plateaus have the same shapes and durations in atmospheric and oceanic records; the implication that atmospheric 14C/12C peaked instantaneously from one plateau to the next; that the 14C plateaus represent 82 % of the total time spent... |
| Tipo: Text |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00667/77949/80129.pdf |
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| Bard, Edouard; Menot, Guillemette; Rostek, Frauke; Licari, Laetitia; Boening, Philipp; Edwards, R. Lawrence; Cheng, Hai; Wang, Yongjin; Heaton, Timothy J.. |
| We present a new record of radiocarbon ages measured by accelerator mass spectrometry (AMS) on a deep-sea core collected off the Pakistan Margin. The C-14 ages measured on the planktonic foraminifera Globigerinoides ruber from core MD04-2876 define a high and stable sedimentation rate on the order of 50 cm/kyr over the last 50 kyr. The site is distant from the main upwelling zone of the western Arabian Sea where C-14 reservoir age is large and may be variable. Many independent proxies based on elemental analyses, mineralogy, biomarkers, isotopic proxies, and foraminiferal abundances show abrupt changes correlative with Dansgaard-Oeschger and Heinrich events. It is now common knowledge that these climatic events also affected the Arabian Sea during the last... |
| Tipo: Text |
Palavras-chave: Berian Margin; Pakistan Margin; 14C; Calibration. |
| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37569/35852.pdf |
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| Darfeuil, Sophie; Menot, Guillemette; Giraud, Xavier; Rostek, Frauke; Tachikawa, Kazuyo; Garcia, Marta; Bard, Edouard. |
| This study aims at providing robust temperature reconstructions for a key oceanographic setting in the North Atlantic and at understanding the nature of the temperature signal recorded by the two biomarkers U-37(k) and TEX86, considering season and depth of production. To do so, high-resolution signals of U-37(k) and TEX86 are determined for the last 70kyr for core MD95-2042, located off Portugal. Signals of U-37(k) and TEX86 present a tight correlation, demonstrating a dominant temperature effect. U-37(k) signals correspond well to the annual mean sea surface temperature (SST), whereas TEX86H-derived temperatures are 5.6 degrees C higher, which is unrealistically warm for this area. Unsuitable TEX86 global linear calibrations on the Iberian Margin may... |
| Tipo: Text |
Palavras-chave: Uk'37; TEX86; Iberian Margin; ROMS simulations; Modeled temperature proxy; SST. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53288/54207.pdf |
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| Boening, Philipp; Bard, Edouard; Rose, Jerome. |
| Here we describe a chemical analysis technique for Ca, Fe, K, Sr, Ti, and S using a recently developed Micro-XRF analyzer (Micro-XRF) with a 100-mm resolution and an XRF whole-core scanner (XRF-S) with a 5-mm resolution for selected sediment sections from a continental margin sediment core. The Micro-XRF produces highly resolved element maps of individual sections, and the calculation of individual continuous element profiles is based on overlap measurements of successive sections. By means of discrete subsamples analyzed by ICP-OES, the two XRF data sets are successfully calibrated to provide quantitative profiles of Ca, Fe, K, Sr, and Ti. We discuss the advantages and limitations of both XRF techniques. A comparison of the two independent XRF data sets... |
| Tipo: Text |
Palavras-chave: Micro-XRF scanner; High-resolution XRF analysis; Major and trace elements. |
| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00235/34614/32957.pdf |
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| Registros recuperados: 11 | |
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