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| Bayon, Germain; Schefuss, Enno; Dupont, Lydie; Borges, Alberto V.; Dennielou, Bernard; Lambert, Thibault; Mollenhauer, Gesine; Monin, Laurence; Ponzevera, Emmanuel; Skonieczny, Charlotte; Andre, Luc. |
| There is increasing evidence that abrupt vegetation shifts and large-scale erosive phases occurred in Central Africa during the third millennium before present. Debate exists as to whether these events were caused by climate change and/or intensifying human activities related to the Bantu expansion. In this study, we report on a multi-proxy investigation of a sediment core (KZR-23) recovered from the Congo submarine canyon. Our aim was to reconstruct climate, erosion and vegetation patterns in the Congo Basin for the last 10,000 yrs, with a particular emphasis on the late Holocene period. Samples of modern riverine suspended particulates were also analyzed to characterize sediment source geochemical signatures from across the Congo watershed. We find that... |
| Tipo: Text |
Palavras-chave: Neodymium isotopes; Suspended particulates; Congo Basin; ENSO; Human land-use; Deforestation. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00463/57467/59747.pdf |
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| Caniupan, Magaly; Lamy, Frank; Lange, Carina B.; Kaiser, Jerome; Kilian, Rolf; Arz, Helge W.; Leon, Tania; Mollenhauer, Gesine; Sandoval, Susana; De Pol-holz, Ricardo; Pantoja, Silvio; Wellner, Julia; Tiedemann, Ralf. |
| Here we provide three new Holocene (11-0 cal ka BP) alkenone-derived sea surface temperature (SST) records from the southernmost Chilean fjord region (50-53 degrees S). SST estimates may be biased towards summer temperature in this region, as revealed by a large set of surface sediments. The Holocene records show consistently warmer than present-day SSTs except for the past similar to 0.6 cal ka BP. However, they do not exhibit an early Holocene temperature optimum as registered further north off Chile and in Antarctica. This may have resulted from a combination of factors including decreased inflow of warmer open marine waters due to lower sea-level stands, enhanced advection of colder and fresher inner fjord waters, and stronger westerly winds. During... |
| Tipo: Text |
Palavras-chave: Holocene; Alkenones; Sea-surface temperature; Fjords; Chile. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00290/40088/39292.pdf |
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| Max, Lars; Riethdorf, Jan-rainer; Tiedemann, Ralf; Smirnova, Maria; Lembke-jene, Lester; Fahl, Kirsten; Nuernberg, Dirk; Matul, Alexander; Mollenhauer, Gesine. |
| Past changes in North Pacific sea surface temperatures and sea-ice conditions are proposed to play a crucial role in deglacial climate development and ocean circulation but are less well known than from the North Atlantic. Here, we present new alkenone-based sea surface temperature records from the subarctic northwest Pacific and its marginal seas (Bering Sea and Sea of Okhotsk) for the time interval of the last 15 kyr, indicating millennial-scale sea surface temperature fluctuations similar to short-term deglacial climate oscillations known from Greenland ice core records. Past changes in sea-ice distribution are derived from relative percentage of specific diatom groups and qualitative assessment of the IP25 biomarker related to sea-ice diatoms. The... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00265/37630/36988.pdf |
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| Meyer, Vera D.; Max, Lars; Hefter, Jens; Tiedemann, Ralf; Mollenhauer, Gesine. |
| It has been proposed that North Pacific sea surface temperature (SST) evolution was intimately linked to North Atlantic climate oscillations during the last glacial-interglacial transition. However, during the early deglaciation and the Last Glacial Maximum, the SST development in the subarctic northwest Pacific and the Bering Sea is poorly constrained as most existing deglacial SST records are based on alkenone paleothermometry, which is limited prior to 15ka B.P. in the subarctic North Pacific realm. By applying the TEX86L temperature proxy we obtain glacial-Holocene-SST records for the marginal northwest Pacific and the Western Bering Sea. Our TEX86L-based records and existing alkenone data suggest that during the past 15.5ka, SSTs in the northwest... |
| Tipo: Text |
Palavras-chave: TEX86L; Surface circulation; Northwest Pacific; Bering Sea; Deglaciation. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53231/54786.pdf |
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| Ronge, Thomas A.; Prange, M.; Mollenhauer, Gesine; Ellinghausen, Maret; Kuhn, G.; Tiedemann, R.. |
| It is widely assumed that the ventilation of the Southern Ocean played a crucial role in driving glacial‐interglacial atmospheric CO2‐levels. So far however, ventilation records from the Indian sector of the Southern Ocean, are widely missing. Here we present reconstructions of water residence times (depicted as ΔΔ14C and Δδ13C) for the last 32,000 years on sediment records from the Kerguelen Plateau and the Conrad Rise (~570‐2500 m water depth), along with simulated changes in ocean stratification from a transient climate model experiment. Our data indicate that Circumpolar Deep Waters in the Indian Ocean were part of the glacial carbon pool. At our sites, close to or bathed by upwelling deep‐waters, we find two pulses of decreasing ΔΔ14C and δ13C values... |
| Tipo: Text |
Palavras-chave: Radiocarbon; Ventilation; Southern Ocean; Younger Dryas; Carbon cycle; Indian Ocean. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00611/72351/71258.pdf |
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| Waelbroeck, Claire; Lougheed, Bryan C.; Vazquez Riveiros, Natalia; Missiaen, Lise; Pedro, Joel; Dokken, Trond; Hajdas, Irka; Wacker, Lukas; Abbott, Peter; Dumoulin, Jean-pascal; Thil, François; Eynaud, Frédérique; Rossignol, Linda; Fersi, Wiem; Albuquerque, Ana Luiza; Arz, Helge; Austin, William E. N.; Came, Rosemarie; Carlson, Anders E.; Collins, James A.; Dennielou, Bernard; Desprat, Stéphanie; Dickson, Alex; Elliot, Mary; Farmer, Christa; Giraudeau, Jacques; Gottschalk, Julia; Henderiks, Jorijntje; Hughen, Konrad; Jung, Simon; Knutz, Paul; Lebreiro, Susana; Lund, David C.; Lynch-stieglitz, Jean; Malaizé, Bruno; Marchitto, Thomas; Martínez-méndez, Gema; Mollenhauer, Gesine; Naughton, Filipa; Nave, Silvia; Nürnberg, Dirk; Oppo, Delia; Peck, Victoria; Peeters, Frank J. C.; Penaud, Aurélie; Portilho-ramos, Rodrigo Da Costa; Repschläger, Janne; Roberts, Jenny; Rühlemann, Carsten; Salgueiro, Emilia; Sanchez Goni, Maria Fernanda; Schönfeld, Joachim; Scussolini, Paolo; Skinner, Luke C.; Skonieczny, Charlotte; Thornalley, David; Toucanne, Samuel; Rooij, David Van; Vidal, Laurence; Voelker, Antje H. L.; Wary, Mélanie; Weldeab, Syee; Ziegler, Martin. |
| Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00513/62429/66712.pdf |
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| Ho, Sze Ling; Mollenhauer, Gesine; Lamy, Frank; Martinez-garcia, Alfredo; Mohtadi, Mahyar; Gersonde, Rainer; Hebbeln, Dierk; Nunez-ricardo, Samuel; Rosell-mele, Antoni; Tiedemann, Ralf. |
| In spite of the important role played by the Southern Ocean in global climate, the few existing paleoceanographic records in the east Pacific sector do not extend beyond one glacial-interglacial cycle, hindering circumpolar comparison of past sea surface temperature (SST) evolution in the Southern Ocean. Here we present three alkenone-based Pleistocene SST records from the subantarctic and subtropical Pacific. We use a regional core top calibration data set to constrain the choice of calibrations for paleo SST estimation. Our core top data confirm that the alkenone-based U-37(K) and U-37(K') values correlate linearly with the SST, in a similar fashion as the most commonly used laboratory culture-based calibrations even at low temperatures (down to similar... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00265/37610/36990.pdf |
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