Consulta: subjectFacets:"Last deglaciation"
Registros recuperados: 12
Data/hora: 06/06/2024 12:57:25

Low-latitude hydrological cycle and rapid climate changes during the last deglaciation
Provedor de dados: 5
Autores: Levi, Camille; Labeyrie, Laurent; Bassinot, Franck; Guichard, Francois; Cortijo, Elsa; Waelbroeck, Claire; Caillon, Nicolas; Duprat, Josette; De Garidel-thoron, Thibault; Elderfield, Harry.
Sea surface temperature and oxygen isotopic records from two well-dated Indian Ocean cores covering the last deglaciation show the occurrence of two periods of increased salinity along the route of warm surface water transport from the Indian to the Atlantic Ocean, one between 18 and 14.5 ka and the other during the Younger Dryas. Our results imply that during these periods, salt accumulated in the tropical Atlantic, creating favorable conditions for an abrupt resumption of the thermohaline circulation and abrupt northern hemisphere warming. Furthermore, we suggest that the observed pattern of millennial climate variability during the last glacial and deglaciation resulted from the interaction between the relatively slow rhythm of expansion and decay of...
Tipo: Text
Palavras-chave: Rapid climate changes; Low-latitude hydrological cycle; Last deglaciation.
Ano: 2007
URL: https://archimer.ifremer.fr/doc/00235/34611/32960.pdf

Climatic evolution of the central equatorial Pacific since the Last Glacial Maximum
Provedor de dados: 5
Autores: Seo, Inah; Lee, Yuri; Lee, Yong Il; Yoo, Chan Min; Hyeong, Kiseong.
This paper investigates paleoceanographic changes at a central equatorial Pacific site (6 degrees 40N, 177 degrees 28W) since the last glacial maximum using planktic foraminifera assemblages, together with the oxygen isotope (O-18) and Mg/Ca compositions of three species (Globigerinoides sacculifer, Pulleniatina obliquiloculata, and Globorotalia tumida) that dwell in the mixed layer, upper thermocline, and lower thermocline, respectively. While the Mg/Ca-derived temperatures of the mixed layer and lower thermocline varied within a narrow range from 18 ka onward, the upper thermocline temperature increased by as much as 3 degrees C during the last deglaciation (18-12 ka) with a simultaneous decrease of O-18. These changes are best explained by an enhanced...
Tipo: Text
Palavras-chave: Planktic foraminifera; Geochemistry; Micropaleontology; Paleoceanography; Intertropical Convergence Zone; Last deglaciation.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00496/60721/65271.pdf

The timing of deglacial circulation changes in the Atlantic
Provedor de dados: 5
Autores: 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

Response of the northwestern Pacific upper water delta C-13 to the last deglacial ventilation of the deep Southern Ocean
Provedor de dados: 5
Autores: Chen, Shaungxi; Li, Tiegang; Tang, Zheng; Qiu, Xiaohua; Xiong, Zhifang; Nan, Qingyun; Xu, Zhaokai; Chang, Fengming.
The deglacial delta C-13 minimum events that originated from the ventilation of the deep Southern Ocean around Antarctica, have been recorded in a range of marine sediments from the southern to tropical oceans in late Pleistocene. However, the broad delta C-13 minimum event was also reported as far as to the northern middle latitudes, in northwestern Pacific marginal sea areas, during the last deglaciation. In the northwestern Pacific, forcing from the northern high latitudes is strongly expressed, while the records of influence from the southern high latitudes are few. The Kuroshio Source Region (KSR) forms a boundary between the northwestern Pacific and the southern, tropical Pacific. So, high-resolution planktonic foraminiferal records in core MD06-3054...
Tipo: Text
Palavras-chave: Planktonic foraminiferal delta C-13; Ventilation of the deep Southern Ocean; Northwestern Pacific; Last deglaciation; Delta C-13 minimum event.
Ano: 2011
URL: https://archimer.ifremer.fr/doc/00213/32467/30934.pdf

Turbiditic levee deposition in response to climate changes: The Var Sedimentary Ridge (Ligurian Sea)
Provedor de dados: 5
Autores: Jorry, Stephan; Jegou, Isabelle; Emmanuel, Laurent; Silva Jacinto, Ricardo; Savoye, Bruno.
The Var turbiditic system located in the Ligurian Sea (SE France) is an intermediate mud/sand-rich system. The particularity of the Var deep-sea fan is its single channel with abrupt bends and its asymmetric and hyper-developed levee on the right hand side: the Var Sedimentary Ridge. Long-term sediment accumulation on the Var Sedimentary Ridge makes this an ideal target for studying the link between onshore climate change and deep-sea turbidite stratigraphy. This paper focuses on the establishment of the first detailed stratigraphy of the levee, which is used to analyze the timing of overbank deposition throughout the last deglaciation. Main results indicate that high variability in turbidite frequencies and deposition rates along the Var Sedimentary Ridge...
Tipo: Text
Palavras-chave: Last deglaciation; Overbank deposits; Turbidity currents; Var Sedimentary Ridge; Ligurian Sea.
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00030/14104/11370.pdf

Evolution of South Atlantic density and chemical stratification across the last deglaciation
Provedor de dados: 5
Autores: Roberts, Jenny; Gottschalk, Julia; Skinner, Luke C.; Peck, Victoria L.; Kender, Sev; Elderfield, Henry; Waelbroeck, Claire; Riveiros, Natalia Vazquez; Hodell, David A.
Explanations of the glacial-interglacial variations in atmospheric pCO(2) invoke a significant role for the deep ocean in the storage of CO2. Deep-ocean density stratification has been proposed as a mechanism to promote the storage of CO2 in the deep ocean during glacial times. A wealth of proxy data supports the presence of a "chemical divide" between intermediate and deep water in the glacial Atlantic Ocean, which indirectly points to an increase in deep-ocean density stratification. However, direct observational evidence of changes in the primary controls of ocean density stratification, i.e., temperature and salinity, remain scarce. Here, we use Mg/Ca-derived seawater temperature and salinity estimates determined from temperature-corrected delta O-18...
Tipo: Text
Palavras-chave: South Atlantic; Density gradient; Ocean stratification; Last deglaciation; Atmospheric CO2.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00421/53276/54569.pdf

A Synthesis of Deglacial Deep-Sea Radiocarbon Records and Their (In)Consistency With Modern Ocean Ventilation
Provedor de dados: 5
Autores: Zhao, Ning; Marchal, Olivier; Keigwin, Lloyd; Amrhein, Daniel; Gebbie, Geoffrey.
We present a synthesis of 1,361 deep-sea radiocarbon data spanning the past 40kyr and computed (for C-14-dated records) from the same calibration to atmospheric C-14. The most notable feature in our compilation is a long-term Delta C-14 decline in deep oceanic basins over the past 25kyr. The Delta C-14 decline mirrors the drop in reconstructed atmospheric Delta C-14, suggesting that it may reflect a decrease in global C-14 inventory rather than a redistribution of C-14 among different reservoirs. Motivated by this observation, we explore the extent to which the deep water C-14 data jointly require changes in basin-scale ventilation during the last deglaciation, based on the fit of a 16-box model of modern ocean ventilation to the deep water Delta C-14...
Tipo: Text
Palavras-chave: Last deglaciation; Ocean ventilation; Data synthesis; Radiocarbon; Inverse method.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00496/60790/64955.pdf

Activity of the turbidite levees of the Celtic-Armorican margin (Bay of Biscay) during the last 30,000 years: Imprints of the last European deglaciation and Heinrich events
Provedor de dados: 5
Autores: Toucanne, Samuel; Zaragosi, S; Bourillet, Jean-francois; Naughton, F; Cremer, M; Eynaud, F; Dennielou, Bernard.
High-resolution sedimentological and micropaleontological studies of several deep-sea cores retrieved from the levees of the Celtic and Armorican turbidite systems (Bay of Biscay - North Atlantic Ocean) allow the detection of the major oscillations of the British-Irish Ice Sheet (BIIS) and 'Fleuve Manche' palaeoriver discharges over the last 30,000 years, which were mainly triggered by climate changes. Between 30 and 20 cal ka, the turbiditic activity on the Celtic-Annorican margin was weak, contrasting with previous stratigraphic models which predicted a substantial increase of sediment supply during low sea-level stands. This low turbidite deposit frequency was most likely the result of a weak activity of the 'Fleuve Manche' palaeoriver and/or of a...
Tipo: Text
Palavras-chave: Turbidites; Heinrich events; LGM; Last deglaciation; Palaeoriver; Fleuve Manche; British irish ice sheet; Bay of Biscay.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-3729.pdf

Environmental significance of microbialites in reef environments during the last deglaciation
Provedor de dados: 5
Autores: Camoin, G; Cabioch, G; Eisenhauer, A; Braga, J; Hamelin, B; Lericolais, Gilles.
In situ microbialites occurring in reef rocks dredged between 80 and 130 in water depth on the modern fore-reef slopes of Tahiti and the Marquesas islands yield ages ranging from 17,100 2900 to 4410 2250 years BP, suggesting that they played a prominent role during the last deglacial sea level rise.   Microbialites developed in both shallow and deep water depositional environments where they characterize various zones of the reef tracts (reef crests, upper reef slopes, deep fore-reef slopes), reflecting contrasting scenarios of microbialite development involving ''reefal microbialites'' in shallow-water settings and ''slope microbialites'' that formed in environments deeper than 1020 in and extending down to more than 100 m.   Reefal microbialites...
Tipo: Text
Palavras-chave: Sea level changes; Nutrients; French polynesia; Holocene; Last deglaciation; Microbialites; Coral reefs.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/2006/publication-4204.pdf

Cold-water coral mounds in the southern Alboran Sea (western Mediterranean Sea): Internal waves as an important driver for mound formation since the last deglaciation
Provedor de dados: 5
Autores: Wang, Haozhuang; Lo Iacono, Claudio; Wienberg, Claudia; Titschack, Jürgen; Hebbeln, Dierk.
Cold-water corals (CWCs) are widely distributed in the entire Alboran Sea (western Mediterranean Sea), but only along the Moroccan margin they have formed numerous coral mounds, which are constrained to the West and the East Melilla CWC mound provinces (WMCP and EMCP). While information already exists about the most recent development of the coral mounds in the EMCP, the temporal evolution of the mounds in the WMCP was unknown up to the present. In this study, we present for the first time CWC ages obtained from four sediment cores collected from different mounds of the WMCP, which allowed to decipher their development since the last deglaciation. Our results revealed two pronounced periods of coral mound formation. The average mound aggradation rates were...
Tipo: Text
Palavras-chave: Cold-water coral mounds; Coral mound formation; Mound aggradation rate; Last deglaciation; Internal waves; Levantine Intermediate Water; Alboran Sea.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00483/59512/83481.pdf

Hydrographic changes in the tropical and extratropical Pacific during the last deglaciation
Provedor de dados: 5
Autores: Rodriguez-sanz, Laura; Graham Mortyn, P.; Herguera, Juan C.; Zahn, Rainer.
Fine-scale, paired Mg/Ca-O-18 profiles (Globigerinoides ruber white, sensu lato) from the San Lazaro Basin (SLB) at 25 degrees N in the Northeast Pacific reveal a transition from a predominant presence of tropical/subtropical waters during the last glacial termination (T1) to an increasing influence of fresh and cold California Current waters toward the Holocene. Changing atmospheric circulation patterns over the Northeast Pacific in step with the demise of the Northern Hemisphere ice sheets and/or with a shift from El Nino- to La Nina-like conditions toward the Holocene are prime candidates to explain this water mass change. O-18(SW-IVC) increases of similar to 0.5-0.7 during the Younger Dryas (YD) and Heinrich stadial 1 (HS1) at the SLB are observed in a...
Tipo: Text
Palavras-chave: SST; California margin; Last deglaciation.
Ano: 2013
URL: https://archimer.ifremer.fr/doc/00264/37491/35812.pdf

Ocean circulation and climate variability in the western South Atlantic and eastern South America during the last deglaciation
Provedor de dados: 5
Autores: Chiessi, Cristiano Mazur.
The growing impact of human activities on the climate system adds a new dimension of complexity and urgency to climate change research. Human activities may have the potential to push key components of the climate system past critical states into qualitatively different modes of operation, i.e. to exceed a tipping point. This possibility requires additional efforts from the many branches of climate change research in order to improve the accuracy of climate change projections. The examination of past climate records has proven to be a very useful area of climate change research. This thesis tackles two elements of the climate system whose tipping points are currently considered very critical: the Atlantic meridional overturning circulation and South...
Tipo: Text
Palavras-chave: South Atlantic; South America; Last deglaciation; Stable isotopes; Trace elements; Atlantic meridional overturning circulation; South American summer monsoon.
Ano: 2008
URL: https://archimer.ifremer.fr/doc/00495/60660/64157.pdf