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| Timmermann, Axel; Sachs, Julian; Timm, Oliver Elison. |
| Equatorial Pacific SST reconstructions derived from Mg/Ca ratios in planktonic foraminifera Globigerinoides ruber and from alkenone-producing coccolithophorids record different trends throughout the Holocene and the last deglaciation. We set forth the hypothesis that their diverging behavior may be related to different seasonal sensitivities which result from the annually varying production rates of alkenone-producing coccolithophorids and of G. ruber. Using a series of transient paleoclimate model simulations forced with the time-varying forcing history over the last 21 ka, a good qualitative agreement is found between simulated boreal winter temperatures and alkenone-SST reconstructions as well as between simulated boreal summer temperatures and... |
| Tipo: Text |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00290/40134/39215.pdf |
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| Deplazes, Gaudenz; Lueckge, Andreas; Peterson, Larry C.; Timmermann, Axel; Hamann, Yvonne; Hughen, Konrad A.; Roehl, Ursula; Laj, Carlo; Cane, Mark A.; Sigman, Daniel M.; Haug, Gerald H.. |
| During the last glacial period, the North Atlantic region experienced pronounced, millennial-scale alternations between cold, stadial conditions and milder interstadial conditions-commonly referred to as Dansgaard-Oeschger oscillations-as well as periods of massive iceberg discharge known as Heinrich events(1). Changes in Northern Hemisphere temperature, as recorded in Greenland(2-4), are thought to have affected the location of the Atlantic intertropical convergence zone(5,6) and the strength of the Indian summer monsoon(7,8). Here we use high-resolution records of sediment colour-a measure of terrigenous versus biogenic content-from the Cariaco Basin off the coast of Venezuela and the Arabian Sea to assess teleconnections with the North Atlantic climate... |
| Tipo: Text |
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| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37556/35774.pdf |
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| Stockhecke, Mona; Timmermann, Axel; Kipfer, Rolf; Haug, Gerald H.; Kwiecien, Ola; Friedrich, Tobias; Menviel, Laurie; Litt, Thomas; Pickarski, Nadine; Anselmetti, Flavio S.. |
| Millennial to orbital-scale rainfall changes in the Mediterranean region and corresponding variations in vegetation patterns were the result of large-scale atmospheric reorganizations. In spite of recent efforts to reconstruct this variability using a range of proxy archives, the underlying physical mechanisms have remained elusive. Through the analysis of a new high-resolution sedimentary section from Lake Van (Turkey) along with climate modeling experiments, we identify massive droughts in the Eastern Mediterranean for the past four glacial cycles, which have a pervasive link with known intervals of enhanced North Atlantic glacial iceberg calving, weaker Atlantic Meridional Overturning Circulation and Dansgaard-Oeschger cold conditions. On orbital... |
| Tipo: Text |
Palavras-chave: Dansgaard-Oeschger variability; Mediterranean droughts; Milankovitch cycles; Lake Van; ICDP PALEOVAN. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53271/54623.pdf |
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| Dubois, Nathalie; Kienast, Markus; Kienast, Stephanie S.; Timmermann, Axel. |
| Amplifying both internally generated variability and remote climate signals from the Atlantic Ocean via coupled air-sea instabilities, the eastern tropical Pacific (ETP) is well situated to detect past climate changes and variations in Central American wind systems that dynamically link the Atlantic and the Pacific. Here we compare new and previously published alkenone-based sea surface temperature (SST) reconstructions from diverse environments within the ETP, i.e. the Eastern Pacific Warm Pool (EPWP), the equatorial and the northern Peruvian Upwelling regions over the past 100,000 yr. Over this time period, a fairly constant meridional temperature gradient across the region is observed, indicating similar hydro-graphic conditions during glacial and... |
| Tipo: Text |
Palavras-chave: Eastern Pacific; Heinrich events winds sea surface temperature alkenone; EOF. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00290/40127/83000.pdf |
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| Sadatzki, Henrik; Dokken, Trond M.; Berben, Sarah M. P.; Muschitiello, Francesco; Stein, Ruediger; Fahl, Kirsten; Menviel, Laurie; Timmermann, Axel; Jansen, Eystein. |
| The last glacial period was marked by pronounced millennial-scale variability in ocean circulation and global climate. Shifts in sea ice cover within the Nordic Seas are believed to have amplified the glacial climate variability in northern high latitudes and contributed to abrupt, high-amplitude temperature changes over Greenland. We present unprecedented empirical evidence that resolves the nature, timing, and role of sea ice fluctuations for abrupt ocean and climate change 32 to 40 thousand years ago, using biomarker sea ice reconstructions from the southern Norwegian Sea. Our results document that initial sea ice reductions at the core site preceded the major reinvigoration of convective deep-water formation in the Nordic Seas and abrupt Greenland... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00484/59606/62620.pdf |
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