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| Gherardi, Jeanne Marie; Labeyrie, L.; Nave, S.; Francois, R.; Mcmanus, J. F.; Cortijo, E.. |
| Studies from the subtropical western and eastern Atlantic Ocean, using the Pa-231/Th-230 ratio as a kinematic proxy for deep water circulation, provided compelling evidence for a strong link between climate and the rate of meridional overturning circulation (MOC) over the last deglaciation. In this study, we present a compilation of existing and new sedimentary Pa-231/Th-230 records from North Atlantic cores between 1710 and 4550 m water depth. Comparing sedimentary Pa-231/Th-230 from different depths provides new insights into the evolution of the geometry and rate of deep water formation in the North Atlantic during the last 20,000 years. The Pa-231/Th-230 ratio measured in upper Holocene sediments indicates slow water renewal above similar to 2500 m and... |
| Tipo: Text |
Palavras-chave: MOC; North Atlantic; Deglaciation; 231Pa/230Th. |
| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00233/34468/32855.pdf |
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| Debret, M.; Bout-roumazeilles, V.; Grousset, F.; Desmet, M.; Mcmanus, J. F.; Massei, N.; Sebag, D.; Petit, J. -r.; Copard, Y.; Trentesaux, A.. |
| Since the first suggestion of 1500-year cycles in the advance and retreat of glaciers (Denton and Karlen, 1973), many studies have uncovered evidence of repeated climate oscillations of 2500, 1500, and 1000 years. During last glacial period, natural climate cycles of 1500 years appear to be persistent (Bond and Lotti, 1995) and remarkably regular (Mayewski et al., 1997; Rahmstorf, 2003), yet the origin of this pacing during the Holocene remains a mystery (Rahmstorf, 2003), making it one of the outstanding puzzles of climate variability. Solar variability is often considered likely to be responsible for such cyclicities, but the evidence for solar forcing is difficult to evaluate within available data series due to the shortcomings of conventional... |
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| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00233/34454/32880.pdf |
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| Tzedakis, P. C.; Wolff, E. W.; Skinner, L. C.; Brovkin, V.; Hodell, D. A.; Mcmanus, J. F.; Raynaud, D.. |
| Differences in the duration of interglacials have long been apparent in palaeoclimate records of the Late and Middle Pleistocene. However, a systematic evaluation of such differences has been hampered by the lack of a metric that can be applied consistently through time and by difficulties in separating the local from the global component in various proxies. This, in turn, means that a theoretical framework with predictive power for interglacial duration has remained elusive. Here we propose that the interval between the terminal oscillation of the bipolar seesaw and three thousand years (kyr) before its first major reactivation provides an estimate that approximates the length of the sea-level high-stand, a measure of interglacial duration. We apply this... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00266/37694/35838.pdf |
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| Thornalley, D. J. R.; Blaschek, M.; Davies, F. J.; Praetorius, S.; Oppo, D. W.; Mcmanus, J. F.; Hall, I. R.; Kleiven, H.; Renssen, H.; Mccave, I. N.. |
| The overflow of deep water from the Nordic seas into the North Atlantic plays a critical role in global ocean circulation and climate. Approximately half of this overflow occurs via the Iceland-Scotland (I-S) overflow, yet the history of its strength throughout the Holocene (similar to 0-11 700 yr ago, ka) is poorly constrained, with previous studies presenting apparently contradictory evidence regarding its long-term variability. Here, we provide a comprehensive reconstruction of I-S overflow strength throughout the Holocene using sediment grain size data from a depth transect of 13 cores from the Iceland Basin. Our data are consistent with the hypothesis that the main axis of the I-S overflow on the Iceland slope was shallower during the early Holocene,... |
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| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37571/35836.pdf |
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| Tzedakis, P. C.; Drysdale, R. N.; Margari, V.; Skinner, L. C.; Menviel, L.; Rhodes, R. H.; Taschetto, A. S.; Hodell, D. A.; Crowhurst, S. J.; Hellstrom, J. C.; Fallick, A. E.; Grimalt, J. O.; Mcmanus, J. F.; Martrat, B.; Mokeddem, Zohra; Parrenin, F.; Regattieri, E.; Roe, K.; Zanchetta, G.. |
| Considerable ambiguity remains over the extent and nature of millennial/centennial-scale climate instability during the Last Interglacial (LIG). Here we analyse marine and terrestrial proxies from a deep-sea sediment sequence on the Portuguese Margin and combine results with an intensively dated Italian speleothem record and climate-model experiments. The strongest expression of climate variability occurred during the transitions into and out of the LIG. Our records also document a series of multi-centennial intra-interglacial arid events in southern Europe, coherent with cold water-mass expansions in the North Atlantic. The spatial and temporal fingerprints of these changes indicate a reorganization of ocean surface circulation, consistent with... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00461/57261/59304.pdf |
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| Desprat, S.; Goni, M. F. Sanchez; Mcmanus, J. F.; Duprat, J.; Cortijo, E.. |
| We present a new high-resolution marine pollen record from NW Iberian margin sediments (core MD03-2697) covering the interval between 340 000 and 270 000 years ago, a time period centred on Marine Isotope Stage (MIS) 9 and characterized by particular baseline climate states. This study enables the documentation of vegetation changes in the north-western Iberian Peninsula and therefore the terrestrial climatic variability at orbital and in particular at millennial scales during MIS 9, directly on a marine stratigraphy. Suborbital vegetation changes in NW Iberia in response to cool/cold events are detected throughout the studied interval even during MIS 9e ice volume minimum. However, they appear more frequent and of higher amplitude during the 30 000 years... |
| Tipo: Text |
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| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00218/32917/31401.pdf |
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| Berger, A.; Crucifix, M.; Hodell, D. A.; Mangili, C.; Mcmanus, J. F.; Otto-bliesner, B.; Pol, K.; Raynaud, D.; Skinner, L. C.; Tzedakis, P. C.; Wolff, E. W.; Yin, Q. Z.; Abe-ouchi, A.; Barbante, C.; Brovkin, V.; Cacho, I.; Capron, E.; Ferretti, P.; Ganopolski, A.; Grimalt, J. O.; Hoenisch, B.; Kawamura, K.; Landais, A.; Margari, V.; Martrat, B.; Masson-delmotte, V.; Mokeddem, Zohra; Parrenin, F.; Prokopenko, A. A.; Rashid, H.; Schulz, M.; Riveiros, N. Vazquez. |
| Interglacials, including the present (Holocene) period, are warm, low land ice extent (high sea level), end-members of glacial cycles. Based on a sea level definition, we identify eleven interglacials in the last 800,000years, a result that is robust to alternative definitions. Data compilations suggest that despite spatial heterogeneity, Marine Isotope Stages (MIS) 5e (last interglacial) and 11c (similar to 400ka ago) were globally strong (warm), while MIS 13a (similar to 500ka ago) was cool at many locations. A step change in strength of interglacials at 450ka is apparent only in atmospheric CO2 and in Antarctic and deep ocean temperature. The onset of an interglacial (glacial termination) seems to require a reducing precession parameter (increasing... |
| Tipo: Text |
Palavras-chave: Interglacials; Review; Quaternary. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00340/45150/44547.pdf |
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