Consulta: creatorFacets:"Gherardi, Jeanne Marie"
Registros recuperados: 5
Data/hora: 26/07/2024 22:48:08

Atlantic Ocean circulation changes preceded millennial tropical South America rainfall events during the last glacial
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Burckel, Pierre; Waelbroeck, Claire; Gherardi, Jeanne Marie; Pichat, Sylvain; Arz, Helge; Lippold, Joerg; Dokken, Trond; Thil, Francois.
During the last glacial period, Greenland's climate shifted between cold (stadial) and warm (interstadial) phases that were accompanied by ocean circulation changes characterized by reduced Atlantic Meridional Overturning Circulation (AMOC) during stadials. Here we present new data from the western tropical Atlantic demonstrating that AMOC slowdowns preceded some of the large South American rainfall events that took place during stadials. Based on 231Pa/230Th and Ti/Ca measurements in the same sediment core, we determine that the AMOC started to slowdown 1420 ± 250 and 690 ± 180 (1σ) years before the onset of two large precipitation events associated with Heinrich stadials. Our results bring unprecedented evidence that AMOC changes could be at the origin...
Tipo: Text
Palavras-chave: Heinrich stadials; Dansgaard-Oeschger stadials; AMOC; ITCZ; Pa; Th.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00296/40711/39709.pdf

Campagne Interpole MD99-114/ Images V. Atlantique Nord et Mers Actiques du 11/06/99 au 06/09/99
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Gherardi, Jeanne Marie; Labeyrie, L.
Tipo: Text
Ano: 1999
URL: https://archimer.ifremer.fr/doc/00503/61463/65226.pdf

Glacial-interglacial circulation changes inferred from Pa-231/Th-230 sedimentary record in the North Atlantic region
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: 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

Refining benthic foraminiferal Mg/Ca-temperature calibrations using core-tops from the western tropical Atlantic: Implication for paleotemperature estimation
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Tisserand, Amandine A.; Dokken, Trond M.; Waelbroeck, Claire; Gherardi, Jeanne Marie; Scao, Vincent; Fontanier, Christophe; Jorissen, Frans.
Benthic foraminiferal Mg/Ca has been shown to have great potential as a proxy for reconstructing deep water temperatures. However, the exact relationship between Mg uptake in benthic foraminifera and temperature is still ambiguous, and further exploration and refinement is much needed to reduce uncertainties associated with the method. Here, we present new core-top Mg/Ca data from benthic foraminiferal species from the lower part of the thermocline in the western tropical Atlantic (northern Brazilian margin). This area is unusual in that the changes in carbonate chemistry along the transect are very small, making it an ideal region for isolating and studying the role of temperature in the incorporation of Mg into the benthic shells. Our results show that...
Tipo: Text
Palavras-chave: Benthic foraminiferal Mg; Ca; Intermediate water temperature; Equatorial thermocline; Western tropical Atlantic Ocean; Core-tops.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00181/29191/27596.pdf

Testing the Pa-231/Th-230 paleocirculation proxy: A data versus 2D model comparison
Provedor de dados: Institutional Archive of Ifreme (ArchiMer)
Autores: Lippold, Jorg; Gherardi, Jeanne Marie; Luo, Yiming.
Variations of the Atlantic Meridional Overturning Circulation (AMOC) are believed to have crucially influenced Earth's climate due to its key role in the inter-hemispheric redistribution of heat and carbon. To assess its past strength, the sedimentary Pa-231/Th-230 proxy has been developed and improved but also contested due to its sensitivity to other factors beyond ocean circulation. In order to provide a better basis for the understanding of the Atlantic Pa-231/Th-230 system, and therefore to shed light on the controversy, we compare new measurements of Holocene sediments from the north Brazilian margin to water column data and the output of a two-dimensional scavenging-circulation model, based on modern circulation patterns and reversible scavenging...
Tipo: Text
Palavras-chave: 231Pa/230Th; Atlantic Meridional Overturning Circulation; Holocene; Deep sea sediments.
Ano: 2011
URL: https://archimer.ifremer.fr/doc/00215/32576/31045.pdf