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Registros recuperados: 10
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Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum ArchiMer
Waelbroeck, C.; Paul, A.; Kucera, M.; Rosell-mele, A.; Weinelt, M.; Schneider, R.; Mix, A. C.; Abelmann, A.; Armand, L.; Bard, E.; Barker, S.; Barrows, T. T.; Benway, H.; Cacho, I.; Chen, M. T.; Cortijo, E.; Crosta, X.; De Vernal, A.; Dokken, T.; Duprat, J.; Elderfield, H.; Eynaud, F.; Gersonde, R.; Hayes, A.; Henry, M.; Hillaire-marcel, C.; Huang, C. C.; Jansen, E.; Juggins, S.; Kallel, N.; Kiefer, T.; Kienast, M.; Labeyrie, L.; Leclaire, H.; Londeix, L.; Mangin, S.; Matthiessen, J.; Marret, F.; Meland, M.; Morey, A. E.; Mulitza, S.; Pflaumann, U.; Pisias, N. G.; Radi, T.; Rochon, A.; Rohling, E. J.; Sbaffi, L.; Schafer-neth, C.; Solignac, S.; Spero, H.; Tachikawa, K.; Turon, J. -l..
Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s. Since that time, several shortcomings of that earlier effort have become apparent. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the...
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Ano: 2009 URL: https://archimer.ifremer.fr/doc/00218/32914/31395.pdf
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Glacial-interglacial circulation changes inferred from Pa-231/Th-230 sedimentary record in the North Atlantic region ArchiMer
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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Hydrological changes in the Mediterranean Sea over the last 30,000 years ArchiMer
Essallami, L.; Sicre, M. A.; Kallel, N.; Labeyrie, L.; Siani, G..
Sea surface temperatures were reconstructed over the last 30,000 years from alkenone paleothermometry (SST-(alk)) and planktonic foraminifera assemblages using the Modern Analog Technique (MAT) (SST-(foram)) along two cores of the Mediterranean Sea: MD84-632 (Levantine basin) and MD04-2797 (Siculo-Tunisian Strait). Oxygen isotope of planktonic foraminifera G. bulloides for core MD04-2797 and G. ruber for core MD84-632 were also determined. SST-alk in the Levantine basin indicate colder values at the Last Glacial Maximum (LGM) (similar to 14 degrees C) than earlier established from MAT, and a cooling amplitude of 6 degrees-7 degrees C, comparable to the central Mediterranean Sea. Climatic events such as the Younger Dryas (YD) and Heinrich events 1 and 2 (H1...
Tipo: Text Palavras-chave: Paleoclimate; Glacial; Mediterranean; Alkenones; Foraminifera; Marine core.
Ano: 2007 URL: https://archimer.ifremer.fr/doc/00208/31954/30378.pdf
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Late Pleistocene paleoproductivity patterns during the last climatic cycle in the Guyana Basin as revealed by calcareous nannoplankton ArchiMer
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...
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Ano: 2008 URL: https://archimer.ifremer.fr/doc/00240/35111/33608.pdf
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Le carbone 14 : progrès récents et limitations de la méthode de datation IRD
Duplessy, J.C.; Arnold, M.; Bard, E.; Cortijo, E.; Labeyrie, L.; Laj, C.; Lehman, B.; Mazaud, A.; Paterne, M.; Tisnerat, N.; Vidal, L..
La méthode de datation par le carbone 14 a permis l'établissement d'une échelle chronologique du Quaternaire Supérieur et a contribué à la découverte de phénomènes insoupçonnés comme l'existence de variations climatiques abruptes et de grande amplitude pendant la dernière période glaciaire et la déglaciation qui l'a terminée. L'effort continu pour comparer les âges carbone 14 avec les âges calendaires a été maintenant étendu au delà de 30 000 ans, même si le nombre de mesures est encore trop petit pour permettre l'établissement d'une courbe de calibration précise au delà des dix mille dernières années. La comparaison des variations du rapport 14C/12C de l'atmosphère avec celles du champ magnétique terrestre (déduites de l'analyse des carottes de sédiments...
Tipo: Text Palavras-chave: QUATERNAIRE; DATATION ABSOLUE; C 14; GEOCHRONOLOGIE; PALEOCLIMAT; CHAMP MAGNETIQUE.
Ano: 1998 URL: http://www.documentation.ird.fr/hor/fdi:010013863
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Modelling planktic foraminifer growth and distribution using an ecophysiological multi-species approach ArchiMer
Lombard, F.; Labeyrie, L.; Michel, E.; Bopp, L.; Cortijo, E.; Retailleau, S.; Howa, Helene; Jorissen, F..
We present an eco-physiological model reproducing the growth of eight foraminifer species (Neogloboquadrina pachyderma, Neogloboquadrina incompta, Neogloboquadrina dutertrei, Globigerina bulloides, Globigerinoides ruber, Globigerinoides sacculifer, Globigerinella siphonifera and Orbulina universa). By using the main physiological rates of foraminifers (nutrition, respiration, symbiotic photosynthesis), this model estimates their growth as a function of temperature, light availability, and food concentration. Model parameters are directly derived or calibrated from experimental observations and only the influence of food concentration (estimated via Chlorophyll-a concentration) was calibrated against field observations. Growth rates estimated from the model...
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Ano: 2011 URL: https://archimer.ifremer.fr/doc/00249/36050/34585.pdf
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Persistent influence of ice sheet melting on high northern latitude climate during the early Last Interglacial ArchiMer
Govin, A.; Braconnot, P.; Capron, E.; Cortijo, E.; Duplessy, J. -c.; Jansen, E.; Labeyrie, L.; Landais, A.; Marti, O.; Michel, E.; Mosquet, E.; Risebrobakken, B.; Swingedouw, D.; Waelbroeck, C..
Although the Last Interglacial (LIG) is often considered as a possible analogue for future climate in high latitudes, its precise climate evolution and associated causes remain uncertain. Here we compile high-resolution marine sediment records from the North Atlantic, Labrador Sea, Norwegian Sea and the Southern Ocean. We document a delay in the establishment of peak interglacial conditions in the North Atlantic, Labrador and Norwegian Seas as compared to the Southern Ocean. In particular, we observe a persistent iceberg melting at high northern latitudes at the beginning of the LIG. It is associated with (1) colder and fresher surface-water conditions in the North Atlantic, Labrador and Norwegian Seas, and (2) a weaker ventilation of North Atlantic deep...
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Ano: 2012 URL: https://archimer.ifremer.fr/doc/00266/37700/35848.pdf
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Striking forest revival at the end of the Roman Period in north-western Europe ArchiMer
Lambert, Clément; Penaud, A.; Vidal, Marie-odile; Gandini, C.; Labeyrie, L.; Chauvaud, Laurent; Ehrhold, Axel.
The Holocene period (last 11,700 years BP) has been marked by significant climate variability over decadal to millennial timescales. The underlying mechanisms are still being debated, despite ocean–atmosphere–land connections put forward in many paleo-studies. Among the main drivers, involving a cluster of spectral signatures and shaping the climate of north-western Europe, are solar activity, the North Atlantic Oscillation (NAO) varying atmospheric regimes and North Atlantic oceanic gyre dynamics. Over the last 2500 years BP, paleo-environmental signals have been strongly affected by anthropogenic activities through deforestation and land use for crops, grazing, habitations, or access to resources. Palynological proxies (especially pollen grains and...
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Ano: 2020 URL: https://archimer.ifremer.fr/doc/00665/77715/79803.pdf
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The timing of deglacial circulation changes in the Atlantic ArchiMer
Waelbroeck, C.; Skinner, L. C.; Labeyrie, L.; Duplessy, J. -c.; Michel, E.; Vazquez Riveiros, Natalia; Gherardi, J. M.; Dewilde, F..
Well-dated benthic foraminifer oxygen isotopic records (delta O-18) from different water depths and locations within the Atlantic Ocean exhibit distinct patterns and significant differences in timing over the last deglaciation. This has two implications: on the one hand, it confirms that benthic delta O-18 cannot be used as a global correlation tool with millennial-scale precision, but on the other hand, the combination of benthic isotopic records with independent dating provides a wealth of information on past circulation changes. Comparing new South Atlantic benthic isotopic data with published benthic isotopic records, we show that (1) circulation changes first affected benthic delta O-18 in the 1000-2200 m range, with marked decreases in benthic delta...
Tipo: Text Palavras-chave: Atlantic Ocean; Benthic oxygen isotope; Last deglaciation; Ocean circulation.
Ano: 2011 URL: https://archimer.ifremer.fr/doc/00214/32517/31003.pdf
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Volcanics from the Sierra Leone Rise ArchiMer
Hekinian, Roger; Bonte, P.; Dupley, P.l.; Blanc, P.l.; Jehano, C.; Labeyrie, L.; Dupleyssis, J.c..
THE Sierra Leone Rise, located in the east equatorial Atlantic, forms a discontinuous chain of seamounts as shallow as 2 km extending with a general NE-SW trend from near the Sierra Leone Coast of Africa, to the St Paul fracture zone near the Mid-Atlantic Ridge (Fig. 1). The origin of this feature has remained a topic of discussion. Sheridan et al. have hypothesised that the Sierra Leone Rise is a volcanic structure formed at the beginning of the opening of the Atlantic in the early Cretaceous period. [NOT CONTROLLED OCR]
Tipo: Text Palavras-chave: Histoire Ifremer.
Ano: 1979 URL: http://archimer.ifremer.fr/doc/1979/publication-5259.pdf
Registros recuperados: 10
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