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| 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 |
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| Evangelista, H.; Sifeddine, A.; Correge, T.; Servain, J.; Dassie, E. P.; Logato, R.; Cordeiro, R. C.; Shen, C. -c.; Le Cornec, F.; Nogueira, J.; Segal, B.; Castagna, A.; Turcq, B.. |
| Although relatively rare compared to similar latitudes in the Pacific or Indian Oceans, massive coral colonies are present in the Tropical/Equatorial Southwestern Atlantic Ocean. However, detailed geo-chemical compositions of these corals are still largely unknown. In this work, we present growth rates, Sr/Ca, and U/Ca ratios of the coral colony (Siderastrea stellata) sampled at Rocas Atoll, off the Brazilian coast. These variables are primarily affected by sea surface temperature (SST) at seasonal scale, and by wind stress at interannual scale, these results represent a broad new finding. A lower significance at the interannual time scale between Sr/Ca and U/Ca with respect to SST is attributed to the low SST amplitude closed to Equator. An investigation... |
| Tipo: Text |
Palavras-chave: Coral; Siderastrea stellata; Rocas Atoll; ITCZ; Equatorial Atlantic; Wind stress. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00623/73552/73796.pdf |
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| Schmidt, Matthew W.; Spero, Howard J.. |
| Paleoproxy studies show a strong correlation between tropical climate and high-latitude temperature variability recorded in the Greenland ice cores over the last glacial cycle. In particular, abrupt cooling events in the Greenland Ice Sheet Project II delta(18)O ice record appear synchronous with a southward migration of the Intertropical Convergence Zone (ITCZ) in the Atlantic, a weakening of the Indian and East Asian monsoon systems, and a strengthening of the South American monsoon system. Because this high-to-low-latitude climate teleconnection significantly alters the tropical hydrologic cycle around the globe, it plays a critical role in regulating global climate on glacial-interglacial time scales. We compare delta(18)O(seawater) reconstructions (a... |
| Tipo: Text |
Palavras-chave: Hydrologic cycle; Mg/Ca; Quaternary; Tropics; Salinity; ITCZ. |
| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00228/33877/32255.pdf |
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| Chang, Yuan-pin; Wang, Wei-lung; Yokoyama, Yusuke; Matsuzaki, Hiroyuki; Kawahata, Hodaka; Chen, Min-te. |
| High resolution planktic foraminifer fauna assemblage data are used to reconstruct the millennial-scale sea surface temperature (SST) variability of the past 40000 years at an IMAGES core site (MD012404) in the Okinawa Trough in the East China Sea (ECS). The fauna assemblages in core MD012404 are dominated by five species - Globigerinoides ruber, Globigerina bulloides, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, and Globigerinita glutinata, which account for > 70% in relative abundance. Our Q-mode factor analysis decomposed the fauna abundance data into three factors, which indicate cold water mass, warm water mass, and possibly coastal water flow with low salinity in the ECS. The MD012404 fauna data show abrupt changes at similar to 16... |
| Tipo: Text |
Palavras-chave: Planktic foraminifer; Sea surface temperature; ITCZ; East China Sea; Okinawa Trough; IMAGES. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00237/34818/33684.pdf |
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| Reeves, Jessica M.; Bostock, Helen C.; Ayliffe, Linda K.; Barrows, Timothy T.; De Deckker, Patrick; Devriendt, Laurent S.; Dunbar, Gavin B.; Drysdale, Russell N.; Fitzsimmons, Kathryn E.; Gagan, Michael K.; Griffiths, Michael L.; Haberle, Simon G.; Jansen, John D.; Krause, Claire; Lewis, Stephen; Mcgregor, Helen V.; Mooney, Scott D.; Moss, Patrick; Nanson, Gerald C.; Purcell, Anthony; Van Der Kaars, Sander. |
| The tropics are the major source of heat and moisture for the Australasian region. Determining the tropics' response over time to changes in climate forcing mechanisms, such as summer insolation, and the effects of relative sea level on exposed continental shelves during the Last Glacial period, is an ongoing process of re-evaluation. We present a synthesis of climate proxy data from tropical Australasia spanning the last 30,000 years that incorporates deep sea core, coral, speleothem, pollen, charcoal and terrestrial sedimentary records. Today, seasonal variability is governed largely by the annual migration of the inter-tropical convergence zone (ITCZ), influencing this region most strongly during the austral summer. However, the position of the ITCZ has... |
| Tipo: Text |
Palavras-chave: ITCZ; LGM; INTIMATE; Australasia; Indo-Pacific Warm Pool; Tropics; Australian monsoon. |
| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37502/36909.pdf |
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| Malaize, B.; Joly, C.; Venec-peyre, M. -t.; Bassinot, F.; Caillon, N.; Charlier, K.. |
| High-resolution faunal and isotopic analyses of foraminifera were performed on core MD96-2073 (10 degrees 94'N, 52 degrees 62'E, 3142 m depth), located close to Socotra Island in the upwelling area of the Somali Basin ( NW Indian Ocean). This work focuses on Marine Isotopic Stage 6.5 in order to reconstruct paleo-upwelling changes and their links with the Arabian Sea summer monsoon and the migration of the Intertropical Convergence Zone (ITCZ). Correspondence and cluster analyses of planktonic foraminiferal abundances, partly controlled by temperature and water mass productivity, together with an upwelling intensification index, show the occurrence of a strong upwelling between 176 and 165 ka. This upwelling intensification responds to a northward... |
| Tipo: Text |
Palavras-chave: Paleoclimatology; Foraminifera; Isotopes; Indian monsoon; ITCZ; Sapropels; Upwelling. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/00234/34487/33433.pdf |
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