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| Collins, James A.; Govin, A.; Mulitza, Stefan; Heslop, David; Zabel, M.; Hartmann, J.; Rohl, U.; Wefer, Gerold. |
| Relict dune fields that are found at 14° N in the modern-day African Sahel are testament to equatorward expansions of the Sahara desert during the late Pleistocene. However, difficulties of dating dune formation mean that abrupt millennial-scale climate events are not always resolved in these records. High-resolution marine core studies have identified Heinrich Stadials as the dustiest periods of the last glacial, although no studies have mapped the spatio-temporal evolution of dust export from West Africa. We use the major-element composition of four marine sediment cores to reconstruct the spatial extent of Saharan-dust versus river-sediment input to the continental margin from West Africa over the last 60 ka. This allows us to map the position of the... |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00182/29279/27696.pdf |
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| Howe, Jacob N. W.; Piotrowski, Alexander M.; Noble, Taryn L.; Mulitza, Stefan; Chiessi, Cristiano M.; Bayon, Germain. |
| Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial-interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial delta C-13 values in the deep Atlantic Ocean cannot be explained solely by water mass source... |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00343/45386/44888.pdf |
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| Voelpel, Rike; Paul, Andre; Krandick, Annegret; Mulitza, Stefan; Schulz, Michael. |
| We present the first results of the implementation of stable water isotopes in the Massachusetts Institute of Technology general circulation model (MITgcm). The model is forced with the isotopic content of precipitation and water vapor from an atmospheric general circulation model (NCAR IsoCAM), while the fractionation during evaporation is treated explicitly in the MITgcm. Results of the equilibrium simulation under pre-industrial conditions are compared to observational data and measurements of plankton tow records (the oxygen isotopic composition of planktic foraminiferal calcite). The broad patterns and magnitude of the stable water isotopes in annual mean seawater are well captured in the model, both at the sea surface as well as in the deep ocean.... |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00662/77396/79002.pdf |
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| Govin, Aline; Holzwarth, Ulrike; Heslop, David; Keeling, Lara Ford; Zabel, Matthias; Mulitza, Stefan; Collins, James A.; Chiessi, Cristiano M.. |
| Numerous studies use major element concentrations measured on continental margin sediments to reconstruct terrestrial climate variations. The choice and interpretation of climate proxies however differ from site to site. Here we map the concentrations of major elements (Ca, Fe, Al, Si, Ti, K) in Atlantic surface sediments (36 degrees N-49 degrees S) to assess the factors influencing the geochemistry of Atlantic hemipelagic sediments and the potential of elemental ratios to reconstruct different terrestrial climate regimes. High concentrations of terrigenous elements and low Ca concentrations along the African and South American margins reflect the dominance of terrigenous input in these regions. Single element concentrations and elemental ratios including... |
| Tipo: Text |
Palavras-chave: Atlantic surface sediments; Terrigenous input; Major elements. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00214/32550/31035.pdf |
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| Capron, Emilie; Govin, Aline; Stone, Emma J.; Masson-delmotte, Valerie; Mulitza, Stefan; Otto-bliesner, Bette; Rasmussen, Tine L.; Sime, Louise C.; Waelbroeck, Claire; Wolff, Eric W.. |
| The Last Interglacial (LIG, 129-116 thousand of years BP, ka) represents a test bed for climate model feedbacks in warmer-than-present high latitude regions. However, mainly because aligning different palaeoclimatic archives and from different parts of the world is not trivial, a spatio-temporal picture of LIG temperature changes is difficult to obtain. Here, we have selected 47 polar ice core and sub-polar marine sediment records and developed a strategy to align them onto the recent AICC2012 ice core chronology. We provide the first compilation of high-latitude temperature changes across the LIG associated with a coherent temporal framework built between ice core and marine sediment records. Our new data synthesis highlights non-synchronous maximum... |
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Palavras-chave: Last Interglacial period; Marine sediment cores; Ice cores; Data synthesis; Climate model simulations. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00289/40063/39166.pdf |
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| Lippold, Jorg; Gutjahr, Marcus; Blaser, Patrick; Christner, Emanuel; Ferreria, Maria Luiza De Carvalho; Mulitza, Stefan; Christl, Marcus; Wombacher, Frank; Böhm, Evelyn; Antz, Benny; Cartapanis, Olivier; Vogel, Hendrik; Jaccard, Samuel L.. |
| Reconstructing past modes of ocean circulation is an essential task in paleoclimatology and paleoceanography. To this end, we combine two sedimentary proxies, Nd isotopes (epsilon(Nd)) and the Pa-231/Th-230 ratio, both of which are not directly involved in the global carbon cycle, but allow the reconstruction of water mass provenance and provide information about the past strength of overturning circulation, respectively. In this study, combined Pa-231/Th-230 and epsilon(Nd) down-core profiles from six Atlantic Ocean sediment cores are presented. The data set is complemented by the two available combined data sets from the literature. From this we derive a comprehensive picture of spatial and temporal patterns and the dynamic changes of the Atlantic... |
| Tipo: Text |
Palavras-chave: Pa-231/Th-230; Epsilon(Nd); Atlantic Meridional Overturning Circulation; Deep sea sediments; Last Glacial Maximum; Deglaciation. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53236/54762.pdf |
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| Campos, Marilia C.; Chiessi, Cristiano M.; Voigt, Ines; Piola, Alberto R.; Kuhnert, Henning; Mulitza, Stefan. |
| Abrupt millennial-scale climate change events of the last deglaciation (i.e. Heinrich Stadial 1 and the Younger Dryas) were accompanied by marked increases in atmospheric CO2 (CO2atm) and decreases in its stable carbon isotopic ratios (delta C-13), i.e. delta(CO2atm)-C-13, presumably due to out-gassing from the ocean. However, information on the preceding Heinrich Stadials during the last glacial period is scarce. Here we present delta C-13 records from two species of planktonic foraminifera from the western South Atlantic that reveal major decreases (up to 1%) during Heinrich Stadials 3 and 2. These delta C-13 decreases are most likely related to millennial-scale periods of weakening of the Atlantic meridional overturning circulation and the consequent... |
| Tipo: Text |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00420/53162/55294.pdf |
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