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| Caley, Thibaut; Extier, Thomas; Collins, James A.; Schefuss, Enno; Dupont, Lydie; Malaize, Bruno; Rossignol, Linda; Souron, Antoine; Mcclymont, Erin L.; Jimenez-espejo, Francisco J.; Garcia-comas, Carmen; Eynaud, Frederique; Martinez, Philippe; Roche, Didier M.; Jorry, Stephan; Charlier, Karine; Wary, Melanie; Gourves, Pierre-yves; Billy, Isabelle; Giraudeau, Jacques. |
| The past two million years of eastern African climate variability is currently poorly constrained, despite interest in understanding its assumed role in early human evolution1,2,3,4. Rare palaeoclimate records from northeastern Africa suggest progressively drier conditions2,5 or a stable hydroclimate6. By contrast, records from Lake Malawi in tropical southeastern Africa reveal a trend of a progressively wetter climate over the past 1.3 million years7,8. The climatic forcings that controlled these past hydrological changes are also a matter of debate. Some studies suggest a dominant local insolation forcing on hydrological changes9,10,11, whereas others infer a potential influence of sea surface temperature changes in the Indian Ocean8,12,13. Here we show... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00449/56059/57581.pdf |
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| Burckel, Pierre; Waelbroeck, Claire; Luo, Yiming; Roche, Didier M.; Pichat, Sylvain; Jaccard, Samuel L.; Gherardi, Jeanne; Govin, Aline; Lippold, Jörg; Thil, Francois. |
| We reconstruct the geometry and strength of the Atlantic meridional overturning circulation during the Heinrich stadial 2 and three Greenland interstadials of the 2050 ka period based on the comparison of new and published sedimentary Pa-231/Th-230 data with simulated sedimentary Pa-231/Th-230. We show that the deep Atlantic circulation during these interstadials was very different from that of the Holocene. Northern-sourced waters likely circulated above 2500 m depth, with a flow rate lower than that of the present-day North Atlantic deep water (NADW). Southern-sourced deep waters most probably flowed northwards below 4000 m depth into the North Atlantic basin and then southwards as a return flow between 2500 and 4000 m depth. The flow rate of this... |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53212/54867.pdf |
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| Galaasen, Eirik Vinje; Ninnemann, Ulysses S.; Kessler, Augustin; Irvalı, Nil; Rosenthal, Yair; Tjiputra, Jerry; Bouttes, Nathaëlle; Roche, Didier M.; Kleiven, Helga (kikki) F.; Hodell, David A.. |
| Disrupting North Atlantic Deep Water (NADW) ventilation is a key concern in climate projections. We use (sub)centennially resolved bottom water δ13C records that span the interglacials of the last 0.5 million years to assess the frequency of and the climatic backgrounds capable of triggering large NADW reductions. Episodes of reduced NADW in the deep Atlantic, similar in magnitude to glacial events, have been relatively common and occasionally long-lasting features of interglacials. NADW reductions were triggered across the range of recent interglacial climate backgrounds, which demonstrates that catastrophic freshwater outburst floods were not a prerequisite for large perturbations. Our results argue that large NADW disruptions are more easily achieved... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00663/77524/79329.pdf |
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| Bugelmayer-blaschek, Marianne; Roche, Didier M.; Renssen, Hans; Andrews, John T.. |
| The climate of the Holocene, the current interglacial covering the past 11,700 years, has been relatively stable compared to previous periods. Nevertheless, repeating occurrence of rapid natural climate changes that challenged human society are seen in proxy reconstructions. Ocean sediment cores for example display prominent peaks of enhanced ice rafted debris (IRD) during the Holocene with a multidecadal to millennial scale periodicity. Different mechanisms were proposed that caused these enhanced IRD events, for example variations in the incoming total solar irradiance (TSI), volcanic eruptions and the combination of internal climate variability and external forcings. We investigate the probable mechanisms causing the occurrence of IRD-events over the... |
| Tipo: Text |
Palavras-chave: Greenland ice sheet; Holocene; Bond events; Icebergs; Climate modeling. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53253/54711.pdf |
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| Bouttes, Nathaelle; Swingedouw, Didier; Roche, Didier M.; Sanchez-goni, Maria F.; Crosta, Xavier. |
| Atmospheric CO2 levels during interglacials prior to the Mid-Brunhes Event (MBE, similar to 430 kaBP) were around 40 ppm lower than after the MBE. The reasons for this difference remain unclear. A recent hypothesis proposed that changes in oceanic circulation, in response to different external forcings before and after the MBE, might have increased the ocean carbon storage in pre-MBE interglacials, thus lowering atmospheric CO2. Nevertheless, no quantitative estimate of this hypothesis has been produced up to now. Here we use an intermediate complexity model including the carbon cycle to evaluate the response of the carbon reservoirs in the atmosphere, ocean and land in response to the changes of orbital forcings, ice sheet configurations and atmospheric... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00497/60821/65114.pdf |
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