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8. Enhanced climate instability in the North Atlantic and southern Europe during the Last Interglacial

Author

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., 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., and Zanchetta, G.

Abstract

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 low-intensity disruptions of the Atlantic meridional overturning circulation (AMOC). The amplitude of this LIG variability is greater than that observed in Holocene records. Episodic Greenland ice melt and runoff as a result of excess warmth may have contributed to AMOC weakening and increased climate instability throughout the LIG.

Published
2018
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9. Lithospheric structuration onshore-offshore of the Sergipe-Alagoas passive margin, NE Brazil, based on wide-angle seismic data

Author

Pinheiro, Joao Marcelo, Schnurle, Philippe, Evain, Mikael, Afilhado, A., Gallais, Flora, Klingelhoefer, Frauke, Loureiro, Afonso, Fuck, R., Soares, J., Cupertino, J. A., Viana, A., Rabineau, Marina, Baltzer, Agnes, Benabdellouahed, Massinissa, Dias, N., Moulin, Maryline, Aslanian, Daniel, Morvan, Laetitia, Maze, Jean-pierre, Pierre, Delphine, Pitel-roudaut, Mathilde, Rio, I, Alves, D., Barros Junior, P., Biari, Youssef, Corela, C., Crozon, Jacques, Duarte, J. L., Ducatel, Cecile, Falcao, C., Fernagu, Philippe, Le Piver, David, Mokeddem, Zohra, Pelleau, Pascal, Rigoti, C., Roest, Walter, Roudaut, Mickael, Pinheiro, Joao Marcelo, Schnurle, Philippe, Evain, Mikael, Afilhado, A., Gallais, Flora, Klingelhoefer, Frauke, Loureiro, Afonso, Fuck, R., Soares, J., Cupertino, J. A., Viana, A., Rabineau, Marina, Baltzer, Agnes, Benabdellouahed, Massinissa, Dias, N., Moulin, Maryline, Aslanian, Daniel, Morvan, Laetitia, Maze, Jean-pierre, Pierre, Delphine, Pitel-roudaut, Mathilde, Rio, I, Alves, D., Barros Junior, P., Biari, Youssef, Corela, C., Crozon, Jacques, Duarte, J. L., Ducatel, Cecile, Falcao, C., Fernagu, Philippe, Le Piver, David, Mokeddem, Zohra, Pelleau, Pascal, Rigoti, C., Roest, Walter, and Roudaut, Mickael

Abstract

The structure and nature of the crust underlying the Camamu-Almada-Jequitinhonha-Sergipe-Alagoas basins System, in the NE Brazilian margin, were investigated based on the interpretation of 12 wide-angle seismic profiles acquired during the SALSA (Sergipe ALagoas Seismic Acquisition) experiment in 2014. In this work, we present two 220-km-long NW-SE combined wide-angle and reflection seismic profiles, SL 01 and SL 02, that have been acquired using 15 ocean-bottom-seismometers along each profile, offshore the southern part of the Sergipe Alagoas Basin (SAB), north of the Vaza-Barris Transfer zone. The SL 02 has a 150-km long inland continuation with 20 land-seismic-stations until the Sergipano Fold Belt (SFB). Wide-angle seismic forward modeling allows us to precisely divide the crust in three domains: beneath the continental shelf, a ∼100 km wide necking zone is imaged where the continental crust thins from ∼35 km on the Unthinned Continental Domain, which displays a three-layered crust structure, to less than 8 km on the Oceanic Crust Domain. In the necking zone, the upper and the middle layers thin dramatically and almost disappear, while the Moho discontinuity shows clear PmPs. The Continental-Oceanic Crust Boundary (COB) is located at ∼80 km from the coastline and is marked by intracrustal seismic reflectors and changes in the seismic velocity, showing a sharp transition. On profile SL02, the oceanic crust is perturbed by a volcanic edifice together with an anomalous velocity zone underneath the area.

Published
2018
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10. Interglacials of the last 800,000 years

Author

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, 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., and Riveiros, N. Vazquez

Abstract

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 Northern Hemisphere summer insolation), but this condition alone is insufficient. Terminations involve rapid, nonlinear, reactions of ice volume, CO2, and temperature to external astronomical forcing. The precise timing of events may be modulated by millennial-scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere. A variety of temporal trends is observed, such that maxima in the main records are observed either early or late in different interglacials. The end of an interglacial (glacial inception) is a slower process involving a global sequence of changes. Interglacials have been typically 10-30ka long. The combination of minimal reduction in northern summer insolation over the next few orbital cycles, owing to low eccentricity, and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future.

Published
2016
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12. Multiproxy reconstruction of palaeoenvironmental evolution since the Last Glacial Maximum in a fjord environment : Loch Sunart (NW Scotland)

Author

Mokeddem, Zohra, Baltzer, Agnès, Goubert, Evelyne, Clet-Pellerin, Martine, Laboratoire Géophysique et Géodynamique, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), Domaines Océaniques (LDO), Centre National de la Recherche Scientifique (CNRS)-Institut d'écologie et environnement-Observatoire des Sciences de l'Univers-Université de Brest (UBO)-Institut national des sciences de l'Univers (INSU - CNRS), Geological Society, London (special publication), and Baltzer, Agnes

Subjects
[SDE.MCG] Environmental Sciences/Global Changes, [SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, [SDE.MCG]Environmental Sciences/Global Changes, [SDU.STU.ST] Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, [SDU.STU.GP] Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2010

13. Evaluating climatically-driven changes in a Scottish sea loch (fjord) over the last 20,000 years

Author

Baltzer , Agnès, Bates , Richard, Clet-Pellerin , Martine, Mokeddem , Zohra, Bonnot-Courtois , Chantal, Walter-Simonnet , Anne-Véronique, Baltzer, Agnes, Howe, J. A., Austin, W. E. N., Forwick, M. & Paetzel, Littoral, Environnement, Télédétection, Géomatique ( LETG ), Université de Caen Normandie ( UNICAEN ), Normandie Université ( NU ) -Normandie Université ( NU ) -Université d'Angers ( UA ) -Université de Nantes ( UN ) -École pratique des hautes études ( EPHE ) -Université de Brest ( UBO ) -Université de Rennes 2 ( UR2 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ), School of Geography and Geosciences, University of St Andrews [Scotland], Laboratoire Géophysique et Géodynamique, Institut Français de Recherche pour l'Exploitation de la Mer ( IFREMER ), Pôle de recherche pour l'organisation et la diffusion de l'information géographique ( PRODIG ), Université Panthéon-Sorbonne ( UP1 ) -Institut de Recherche pour le Développement ( IRD ) -École pratique des hautes études ( EPHE ) -Université Paris-Sorbonne ( UP4 ) -Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Chrono-environnement ( LCE ), Université Bourgogne Franche-Comté ( UBFC ) -Centre National de la Recherche Scientifique ( CNRS ) -Université de Franche-Comté ( UFC ), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN), School of Geography and Geosciences [St Andrews], Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Pôle de recherche pour l'organisation et la diffusion de l'information géographique (PRODIG), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris-Sorbonne (UP4)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Chrono-environnement - CNRS - UBFC (UMR 6249) (LCE), Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Howe, J. A., Austin, W. E. N., Forwick, and M. & Paetzel

Subjects
[ SDU.STU.GM ] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, [ SDU.STU.ST ] Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment, [ SDU.STU.GP ] Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [ SDE.MCG ] Environmental Sciences/Global Changes, [SDE.MCG] Environmental Sciences/Global Changes, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, [ SDU.ENVI ] Sciences of the Universe [physics]/Continental interfaces, environment, [SDU.STU.ST] Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, [SDU.STU.GP] Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2010

14. A multiproxy palaeoenvironmental reconstruction of Loch Sunart (NW 1 Scotland) since the Last Glacial Maximum

Author

Mokeddem, Zohra, Baltzer, Agnès, Goubert, Evelyne, Clet-Pellerin, Martine, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Université de Bretagne Sud - Vannes (UBS Vannes), and Université de Bretagne Sud (UBS)

Subjects
Sea-loch, [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy, Benthic foraminifera, meltwater pulse, Pollen, Sortable Silt, climate events
Abstract

International audience; Loch Sunart is located on the northwest coast of Scotland and contains a sedimentary sequence that records Late Glacial to Holocene climatic variations. A 12 m core MD04-2833 was acquired in the main basin of the loch sampling this sequence. We present the palaeoenvironmental data and palaeoclimatical scenario, based on a multiproxy approach, using pollen concentrations, sortable silt variation, lithic fraction and marine benthic foraminifera assemblages. These analyses allow the identification of major climate fluctuations such as cooling events. Global temperature decreases are discriminated from local water temperature decreases due to ice-melting processes by the presence of Elphidium subarcticum and the assemblage of Cassidulina obtusa and Haynesina germanica. Two meltwater pulses (MWP) are distinguished, which respectively correspond to the MWP-Ia (15,500–13,000 cal yr BP) and MWP-Ib (12,200–10,100 cal yr BP). After the maximum water stratification occurred at 7,500 cal yr BP, full marine conditions were establishedaround 6,000 cal yr BP, which correspond to the highest relative sea-level reached in the loch.

Published
2010
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