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| 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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| Crosta, X.; Debret, M.; Denis, D.; Courty, M. A.; Ther, O.. |
| Diatom data from a marine sediment core give insight on Holocene changes in sea- surface conditions and climate at high southern latitudes off Adelie Land, East Antarctica. The early to mid- Holocene was warmer than the late Holocene with a transition at similar to 4000 calendar years B. P. Sea ice was less present and spring- summer growing season was greater during the warm period relative to the cold one, thus limiting sea ice diatom production and favoring more open ocean diatom to develop. The long- term Holocene climatic evolution in East Antarctica is explained by a combination of a delayed response to local seasonal insolation changes coupled to the long memory of the Southern Ocean. Abrupt variations of the diatom relative abundances, indicating... |
| Tipo: Text |
Palavras-chave: Antarctica; Sea ice; Holocene; Insolation; Thermohaline circulation. |
| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00235/34642/33044.pdf |
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| Bouttes, N.; Vazquez Riveiros, Natalia; Govin, A.; Swingedouw, D.; Sanchez-goni, M.f.; Crosta, X.; Roche, D.m.. |
| Ice core data have shown that atmospheric CO2 concentrations during interglacials were lower before the Mid Brunhes Event (MBE, ~430 ka), than after the MBE by around 30 ppm. To explain such a difference, it has been hypothesized that increased bottom water formation around Antarctica or reduced Atlantic Meridional Overturning Circulation (AMOC) could have led to greater oceanic carbon storage before the MBE, resulting in less carbon in the atmosphere. However, only few data on possible changes in interglacial ocean circulation across the MBE have been compiled, hampering model‐data comparison. Here we present a new global compilation of benthic foraminifera carbon isotopic (δ13C) records from 31 marine sediment cores covering the last 800 ka, with the aim... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00619/73130/72285.pdf |
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| Hatin, T.; Crosta, X.; Le Herisse, A.; Droz, L.; Marsset, Tania. |
| Changes in siliceous productivity in the eastern Equatorial Atlantic Ocean, off the Western African margin, over the last several glacial cycles have been either related to global-to-regional oceanographic changes (upwelling intensity) or climate changes (precipitation and river discharge). Based on diatom assemblages in core KZAI-02, located to the south of the mouth of the Congo River, integrated with a selection of geochemical proxies, we show that siliceous productivity in the southeastern Angola Basin responded to non-linear interactions between both oceanographic and climate changes over the last 190,000 years. High diatom accumulation rates were recorded in the middle part of MIS 6, in cold substage MIS 5d and in MIS 3-2. During these intervals,... |
| Tipo: Text |
Palavras-chave: Diatoms; Productivity; Late quaternary; Millennial time scale; Congo fan area. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00363/47402/47394.pdf |
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| Dumont, M.; Pichevin, L.; Geibert, W.; Crosta, X.; Michel, E.; Moreton, S.; Dobby, K.; Ganeshram, R.. |
| Changes in ocean circulation and the biological carbon pump have been implicated as the drivers behind the rise in atmospheric CO2 across the last deglaciation; however, the processes involved remain uncertain. Previous records have hinted at a partitioning of deep ocean ventilation across the two major intervals of atmospheric CO2 rise, but the consequences of differential ventilation on the Si cycle has not been explored. Here we present three new records of silicon isotopes in diatoms and sponges from the Southern Ocean that together show increased Si supply from deep mixing during the deglaciation with a maximum during the Younger Dryas (YD). We suggest Antarctic sea ice and Atlantic overturning conditions favoured abyssal ocean ventilation at the YD... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00618/72971/72036.pdf |
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| Mathiot, P.; Goosse, H.; Crosta, X.; Stenni, B.; Braida, M.; Renssen, H.; Van Meerbeeck, C. J.; Masson-delmotte, V.; Mairesse, A.; Dubinkina, S.. |
| From 10 to 8 ka BP (thousand years before present), paleoclimate records show an atmospheric and oceanic cooling in the high latitudes of the Southern Hemisphere. During this interval, temperatures estimated from proxy data decrease by 0.8 degrees C over Antarctica and 1.2 degrees C over the Southern Ocean. In order to study the causes of this cooling, simulations covering the early Holocene have been performed with the climate model of intermediate complexity LOVECLIM constrained to follow the signal recorded in climate proxies using a data assimilation method based on a particle filtering approach. The selected proxies represent oceanic and atmospheric surface temperature in the Southern Hemisphere derived from terrestrial, marine and glaciological... |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00181/29203/27584.pdf |
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| Crosta, X.; Romero, O. E.; Ther, O.; Schneider, R. R.. |
| Opal content and diatom assemblages were analysed in core GeoB4905-4 to reconstruct siliceous productivity changes in the eastern Gulf of Guinea during the last 40 000 yr. Opal and total diatom accumulation rates presented low values over the considered period, except during the Last Glacial Maximum and between 15 000 calendar years Before Present (15 cal. ka BP) and 5.5 cal. ka BP, the so-called African Humid Period, when accumulation rates of brackish and freshwater diatoms at the core site were highest. Conversely, accumulation rates of windblown diatoms exhibited an opposite pattern with higher values before and after the African Humid Period and greatest values during Heinrich Events, the Younger Dryas and since 5.5 cal. ka BP. Our results demonstrate... |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00266/37699/36808.pdf |
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| Romero, O. E.; Crosta, X.; Kim, J. -h.; Pichevin, L.; Crespin, J.. |
| Although productivity variations in coastal upwelling areas are mostly attributed to changes in wind strength, productivity dynamics in the Benguela Upwelling System (BUS) is less straightforward due to its complex atmospheric and hydrographic settings. In view of these settings, past productivity variations in the BUS can be better investigated with downcore sediments representing different productivity regimes. In this study, two sediment cores retrieved at ca. 25°–26°S in the BUS and representing different productivity regimes were studied. By using micropaleontological, geochemical and temperature proxies measured on core MD96-2098, recovered at 2910 m water depth in the bathypelagic zone at 26°S off Namibia, variations of filament front location,... |
| Tipo: Text |
Palavras-chave: Benguela; Diatoms; Millennial and submillennial time scale; Productivity; Sea-surface temperature; SW Atlantic; Upwelling filaments. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00294/40499/39432.pdf |
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| Skonieczny, Charlotte; Paillou, P.; Bory, A.; Bayon, Germain; Biscara, L.; Crosta, X.; Eynaud, F.; Malaize, B.; Revel, M.; Aleman, N.; Barusseau, J-p.; Vernet, R.; Lopez, S.; Grousset, F.. |
| The Sahara experienced several humid episodes during the late Quaternary, associated with the development of vast fluvial networks and enhanced freshwater delivery to the surrounding ocean margins. In particular, marine sediment records off Western Sahara indicate deposition of river-borne material at those times, implying sustained fluvial discharges along the West African margin. Today, however, no major river exists in this area; therefore, the origin of these sediments remains unclear. Here, using orbital radar satellite imagery, we present geomorphological data that reveal the existence of a large buried paleodrainage network on the Mauritanian coast. On the basis of evidence from the literature, we propose that reactivation of this major paleoriver... |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00303/41381/40559.pdf |
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