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| Registros recuperados: 15 | |
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| Mazaud, A.; Michel, Elisabeth; Dewilde, F.; Turon, J. L.. |
| We examine the past variations of the Antarctic Circumpolar Current (ACC) by using variations in size and abundance of the magnetic grains deposited by this current at a site east the Kerguelen-Crozet plateau. Core MD00-2375G was taken at a midlatitude site during the ANTAUS cruise conducted in 2000 by the French R/V Marion Dufresne. Marine isotope stages (MIS) down to MIS 13 are identified, and an age model is derived from a correlation to the ice core isotopic record obtained from EPICA in Antarctica. Continuous records of abundance and size of the magnetic grains were obtained using environmental magnetism methods. Results show a strong modulation of the ACC flow intensity in response to glacial and interglacial cycles. The low abundance and the small... |
| Tipo: Text |
Palavras-chave: Antarctic; Current; Past; Cycles. |
| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00231/34190/32874.pdf |
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| Gottschalk, Julia; Riveiros, Natalia Vazquez; Waelbroeck, Claire; Skinner, Luke C.; Michel, Elisabeth; Duplessy, Jean-claude; Hodell, David; Mackensen, Andreas. |
| Epibenthic foraminifer delta C-13 measurements are valuable for reconstructing past bottom water dissolved inorganic carbon d13C (delta C-13(DIC)), which are used to infer global ocean circulation patterns. Epibenthic delta C-13, however, may also reflect the influence of C-13-depleted phytodetritus, microhabitat changes, and/or variations in carbonate ion concentrations. Here we compare the delta C-13 of two benthic foraminifer species, Cibicides kullenbergi and Cibicides wuellerstorfi, and their morphotypes, in three sub-Antarctic Atlantic sediment cores over several glacial-interglacial transitions. These species are commonly assumed to be epibenthic, living above or directly below the sediment-water interface. While this might be consistent with the... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53207/54927.pdf |
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| Siani, Giuseppe; Michel, Elisabeth; De Pol-holz, Ricardo; Devries, Tim; Lamy, Frank; Carel, Melanie; Isguder, Gulay; Dewilde, Fabien; Lourantou, Anna. |
| The Southern Ocean plays a prominent role in the Earth's climate and carbon cycle. Changes in the Southern Ocean circulation may have regulated the release of CO2 to the atmosphere from a deep-ocean reservoir during the last deglaciation. However, the path and exact timing of this deglacial CO2 release are still under debate. Here we present measurements of deglacial surface reservoir C-14 age changes in the eastern Pacific sector of the Southern Ocean, obtained by C-14 dating of tephra deposited over the marine and terrestrial regions. These results, along with records of foraminifera benthic-planktic C-14 age and delta C-13 difference, provide evidence for three periods of enhanced upwelling in the Southern Ocean during the last deglaciation, supporting... |
| Tipo: Text |
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| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00263/37472/36804.pdf |
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| Peral, Marion; Daeron, Mathieu; Blamart, Dominique; Bassinot, Franck; Dewilde, Fabien; Smialkowski, Nicolas; Isguder, Gulay; Bonnin, Jerome; Jorissen, Frans; Kissel, Catherine; Michel, Elisabeth; Vazquez Riveiros, Natalia; Waelbroeck, Claire. |
| Accurate reconstruction of past ocean temperatures is of critical importance to paleoclimatology. Carbonate clumped isotope thermometry (“Δ47”) is a relatively recent technique based on the strong relationship between calcification temperature and the statistical excess of 13C-18O bonds in carbonates. Its application to foraminifera holds great scientific potential, particularly because Δ47 paleotemperature reconstructions do not require assumptions regarding the 18O composition of seawater. However there are still relatively few published observations investigating the potential influence of parameters such as salinity or foraminiferal size and species. We present a new calibration data set based on 234 replicate analyses of 9 planktonic and 2 benthic... |
| Tipo: Text |
Palavras-chave: Carbonate clumped isotopes; Foraminifera; Paleothermometry. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00450/56134/57676.pdf |
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| Van Rooij, David; Hebbelin, Dierk; Comas, Menchu; Vandorpe, Thomas; Delivet, Stanislas; Nave, Silvia; Michel, Elisabeth; Lebreiro, Susana; Terrinha, Pedro; Roque, Cristina; Anton, Laura; Batista, Luis; And The Md194 Shipboard Scientists,. |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00416/52794/53693.pdf |
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| Gottschalk, Julia; Michel, Elisabeth; Thöle, Lena M.; Studer, Anja S.; Hasenfratz, Adam P.; Schmid, Nicole; Butzin, Martin; Mazaud, Alain; Martínez-garcía, Alfredo; Szidat, Sönke; Jaccard, Samuel L.. |
| Past changes in ocean 14C disequilibria have been suggested to reflect the Southern Ocean control on global exogenic carbon cycling. Yet, the volumetric extent of the glacial carbon pool and the deglacial mechanisms contributing to release remineralized carbon, particularly from regions with enhanced mixing today, remain insufficiently constrained. Here, we reconstruct the deglacial ventilation history of the South Indian upwelling hotspot near Kerguelen Island, using high-resolution 14C-dating of smaller-than-conventional foraminiferal samples and multi-proxy deep-ocean oxygen estimates. We find marked regional differences in Southern Ocean overturning with distinct South Indian fingerprints on (early de-)glacial atmospheric CO2 change. The dissipation of... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00662/77418/79081.pdf |
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| Van Der Putten, Nathalie; Verbruggen, Cyriel; Bjorck, Svante; Michel, Elisabeth; Disnar, Jean-robert; Chapron, Emmanuel; Moine, Bertrand N.; De Beaulieu, Jacques-louis. |
| The awareness of the significance of the Southern Ocean in the Earth's climate system has become increasingly obvious. The deglacial atmospheric CO2 rise during warming periods in Antarctica has been attributed to CO2 ventilation from the deep ocean caused by enhanced upwelling around the Antarctic Divergence. It has been hypothesized that, more intense Southern Hemisphere westerly winds aligned with the Antarctic Circumpolar Current due to a southward shift of the wind belt from its Last Glacial Maximum equator-ward position, are the main drivers. Reconstructions of past changes in atmospheric circulation in the Southern Hemisphere are still scarce and the overall picture is patchy with sometimes contradictory results. For obvious reasons, most... |
| Tipo: Text |
Palavras-chave: Palaeoclimatology; Last Termination; Peat record; Kerguelen Islands; Southern Ocean; Indian Ocean; Oceanic Cold Reversal; Southern Hemisphere westerly belt. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00497/60843/64283.pdf |
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| Schmittner, Andreas; Bostock, Helen C.; Cartapanis, Olivier; Curry, William B.; Filipsson, Helena L.; Galbraith, Eric D.; Gottschalk, Julia; Carlos Herguera, Juan; Hoogakker, Babette; Jaccard, Samuel L.; Lisiecki, Lorraine E.; Lund, David C.; Martinez-mendez, Gema; Lynch-stieglitz, Jean; Mackensen, Andreas; Michel, Elisabeth; Mix, Alan C.; Oppo, Delia W.; Peterson, Carlye D.; Repschlaeger, Janne; Sikes, Elisabeth L.; Spero, Howard J.; Waelbroeck, Claire. |
| The carbon isotope composition (C-13) of seawater provides valuable insight on ocean circulation, air-sea exchange, the biological pump, and the global carbon cycle and is reflected by the C-13 of foraminifera tests. Here more than 1700 C-13 observations of the benthic foraminifera genus Cibicides from late Holocene sediments (C-13(Cibnat)) are compiled and compared with newly updated estimates of the natural (preindustrial) water column C-13 of dissolved inorganic carbon (C-13(DICnat)) as part of the international Ocean Circulation and Carbon Cycling (OC3) project. Using selection criteria based on the spatial distance between samples, we find high correlation between C-13(Cibnat) and C-13(DICnat), confirming earlier work. Regression analyses indicate... |
| Tipo: Text |
Palavras-chave: Carbon; Isotopes; Benthic; Foraminifera; Calibration. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00661/77326/78788.pdf |
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| Fossile, Eleonore; Nardelli, Maria Pia; Jouini, Arbia; Lansard, Bruno; Pusceddu, Antonio; Moccia, Davide; Michel, Elisabeth; Péron, Olivier; Howa, Hélène; Mojtahid, Meryem. |
| The rapid response of benthic foraminifera to environmental factors (e.g., organic matter quality and quantity, salinity, pH) and their high fossilisation potential make them promising bio-indicators for the intensity and recurrence of brine formation in Arctic seas. Such approach, however, requires a thorough knowledge of their modern ecology in such extreme settings. To this aim, seven stations along a N–S transect across the Storfjorden (Svalbard archipelago) have been sampled using an interface multicorer. This fjord is an area of intense sea ice formation characterised by the production of Brine-enriched Shelf Waters (BSW) as a result of a recurrent latent-heat polynya. Living (Rose Bengal stained) foraminiferal assemblages were analysed together with... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00599/71122/69424.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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| Barras, C.; Duplessy, J. -c.; Geslin, E.; Michel, Elisabeth; Jorissen, F. J.. |
| The geochemical composition of deep-sea benthic foraminiferal calcite is widely used to reconstruct sea floor paleoenvironments. The calibration of the applied proxy methods has until now been based on field observations in complex natural ecosystems where multiple factors are interfering. However, laboratory experiments with stable physico-chemical conditions appear to be the ideal way to evaluate the influence of a single parameter. In this paper, we present the oxygen isotopic composition of deep-sea benthic foraminiferal shells entirely calcified under controlled experimental conditions over a large temperature range (4 to 19 degrees C). The new laboratory protocols developed for this study allowed us to produce large quantities of shells in stable... |
| Tipo: Text |
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| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00241/35177/33738.pdf |
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| Riveiros, Natalia Vazquez; Govin, Aline; Waelbroeck, Claire; Mackensen, Andreas; Michel, Elisabeth; Moreira, Santiago; Bouinot, Thomas; Caillon, Nicolas; Orgun, Ayche; Brandon, Margaux. |
| Planktic foraminiferal Mg/Ca ratios have become a fundamental seawater temperature proxy in past climate reconstructions, due to the temperature dependence of Mg uptake into foraminiferal calcite. However, empirical calibrations for single species from methodologically consistent data are still lacking. Here we present species-specific calibrations of Mg/Ca versus calcification temperature for two commonly used species of planktic foraminifera: Globigerina bulloides and Neogloboquadrina pachyderma left, based on a series of Southern Ocean and North Atlantic core tops. Combining these new data with previously published data, we derive an integrated G. bulloides Mg/Ca-temperature calibration for mid and high latitudes of both hemispheres between 2 and 18°C,... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00324/43480/42916.pdf |
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| Govin, Aline; Michel, Elisabeth; Labeyrie, Laurent; Waelbroeck, Claire; Dewilde, Fabien; Jansen, Eystein. |
| We investigated deep water changes in the Southern Ocean during the last glacial inception, in relationship to surface hydrology and global climatology, to better understand the mechanisms of the establishment of a glacial ocean circulation. Changes in benthic foraminiferal delta(13)C from three high-resolution cores are compared and indicate decoupled intermediate and deep water changes in the Southern Ocean. From the comparison with records from the North Atlantic, South Atlantic, and the Southern Ocean, we show that the early southern deep water delta(13)C drop observed at the MIS 5.5-5.4 transition occurred before any significant reduction of North Atlantic Deep Water ventilation. We propose that this drop is linked to the northward expansion of poorly... |
| Tipo: Text |
Palavras-chave: Isotope substage 5E; Ice core; Interglacial period; Climate variability; Deep ocean; Atlantic; Sea; Circulation; Temperature; Hemisphere. |
| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00208/31952/30375.pdf |
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| López-otálvaro, G.-e.; Flores, J. A.; Sierro, F. J.; Cacho, I.; Grimalt, J.-o.; Michel, Elisabeth; Cortijo, E.; Labeyrie, L.. |
| Variations in the assemblages and abundances of calcareous nannoplankton have allowed us to interpret changes in oceanic and atmospheric dynamics in the Guyana Basin, mainly linked to the southeast trades over the last climatic cycle. Records of the paleoproductivity index of coccolithophores (N ratio) allowed us to monitor the nutri-thermocline fluctuations. Additionally, nannofossil accumulation rates vary closely with the N ratio, indicating a strong correlation between these two paleoproductivity proxies. The dominance of upper (small Noelaerhabdaceae, Emiliania huxleyi and Gephyrocapsa oceanica), over lower photic zone dwellers (Florisphaera profunda) during Termination II and interglacial substages 5.1 and 5.3 is related to eutrophic conditions due... |
| Tipo: Text |
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| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00240/35111/33608.pdf |
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| Registros recuperados: 15 | |
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