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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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| Cornuault, Marine; Tachikawa, Kazuyo; Vidal, Laurence; Guihou, Abel; Siani, Giuseppe; Deschamps, Pierre; Bassinot, Franck; Revel, Marie. |
| The Eastern Mediterranean Sea (EMS) is a key region to study circulation change because of its own thermohaline circulation. In this study, we focused on intermediate/deep water circulation since the Last Glacial Maximum (LGM) including the sapropel S1 period. Two cores from the Levantine Sea and the Strait of Sicily, respectively, collected at 1,780 m and 771 m water depth, were studied using Nd-143/Nd-144 (epsilon(Nd)) of foraminiferal tests and leachates as well as benthic foraminiferal stable isotopes (delta C-13, delta O-18). This approach allowed the determination of variations in (1) the North Atlantic water contribution to the Mediterranean basin, (2) water exchanges at the Strait of Sicily, and (3) the influence of the Nile River over the last... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00496/60789/64957.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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| Jaouadi, Sahbi; Lebreton, Vincent; Bout-roumazeilles, Viviane; Siani, Giuseppe; Lakhdar, Rached; Boussoffara, Ridha; Dezileau, Laurent; Kallel, Nejib; Mannai-tayech, Beya; Combourieu-nebout, Nathalie. |
| Pollen and clay mineralogical analyses of a Holocene sequence from Sebkha Boujmel (southern Tunisia) trace the climatic and environmental dynamics in the lower arid bioclimatic zone over the last 8000 years. During the mid- to late Holocene transition, between ca. 8 and 3aEuro-kaaEuro-BP, a succession of five wet-dry oscillations is recorded. An intense arid event occurs between ca. 5.7 and 4.6aEuro-kaaEuro-BP. This episode marks the onset of a long-term aridification trend with a progressive retreat of Mediterranean woody xerophytic vegetation and of grass steppes. It ends with the establishment of pre-desert ecosystems around 3aEuro-kaaEuro-BP. The millennial-scale climate change recorded in the data from Sebkha Boujmel is consistent with records from... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53281/54321.pdf |
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| Dubois-dauphin, Quentin; Montagna, Paolo; Siani, Giuseppe; Douville, Eric; Wienberg, Claudia; Hebbeln, Dierk; Liu, Zhifei; Kallel, Nejib; Dapoigny, Arnaud; Revel, Marie; Pons-branchu, Edwige; Taviani, Marco; Colin, Christophe. |
| We present the neodymium isotopic composition (epsilon Nd) of mixed planktonic foraminifera species from a sediment core collected at 622m water depth in the Balearic Sea, as well as epsilon Nd of scleractinian cold-water corals (CWC; Madrepora oculata, Lophelia pertusa) retrieved between 280 and 442m water depth in the Alboran Sea and at 414m depth in the southern Sardinian continental margin. The aim is to constrain hydrological variations at intermediate depths in the western Mediterranean Sea during the last 20 kyr. Planktonic (Globigerina bulloides) and benthic (Cibicidoides pachyderma) foraminifera from the Balearic Sea were also analyzed for stable oxygen (delta O-18) and carbon (delta C-13) isotopes. The foraminiferal and coral epsilon Nd values... |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00420/53193/55001.pdf |
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| Magny, Michel; Combourieu Nebout, Nathalie; De Beaulieu, Jacques-louis; Bout-roumazeilles, Viviane; Colombaroli, D.; Desprat, Stephanie; Francke, A.; Joannin, Sebastien; Ortu, Elena; Peyron, Odile; Revel, Marie; Sadori, Laura; Siani, Giuseppe; Sicre, Marie-alexandrine; Samartin, S.; Simonneau, A.; Tinner, Willy; Vanniere, Boris; Wagner, B.; Zanchetta, Giovanni; Anselmetti, Flavio S.; Brugiapaglia, E.; Chapron, Emmanuel; Debret, Maxime; Desmet, Marc; Didier, Jean; Essallami, Latifa; Galop, D.; Gilli, A.; Haas, J.n.; Kallel, Nejib; Millet, L.; Stock, Andy; Turon, Jean-louis; Wirth, S.. |
| On the basis of a multi-proxy approach and a strategy combining lacustrine and marine records along a north-south transect, data collected in the central Mediterranean within the framework of a collaborative project have led to reconstruction of high-resolution and well-dated palaeohydrological records and to assessment of their spatial and temporal coherency. Contrasting patterns of palaeohydrological changes have been evidenced in the central Mediterranean: south (north) of around 40 degrees N of latitude, the middle part of the Holocene was characterised by lake-level maxima (minima), during an interval dated to ca. 10 300-4500 cal BP to the south and 9000-4500 cal BP to the north. Available data suggest that these contrasting palaeohydrological... |
| Tipo: Text |
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| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37570/36902.pdf |
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| Wils, Katleen; Daele, Maarten Van; Kissel, Catherine; Moernaut, Jasper; Schmidt, Sabine; Siani, Giuseppe; Lastras, Galderic. |
| Grain‐size analysis and end‐member modelling of a long sediment core from Aysén Fjord (southern Chile) allows to identify over 25 seismo‐turbidites in the last 9000 years. Considering the shaking intensities required to trigger these turbidites (V½‐VI½), the majority can be related to megathrust earthquakes. Multiple studies in south‐central Chile have aimed at finding traces of giant, tsunamigenic megathrust earthquakes leading to the current 5500‐year‐long paleoseismological record of the Valdivia Segment. However, none of these cover the southern third of the segment. Aysén Fjord allows to fill this data gap and presents the first, crucial paleoseismic data to demonstrate that the 1960 event was not unique for the Valdivia Segment, yielding a recurrence... |
| Tipo: Text |
Palavras-chave: Megathrust earthquakes; Turbidite paleoseismology; Valdivia segment; South-central Chile; Variable rupture mode. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00646/75832/76820.pdf |
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