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  • 1
    Publication Date: 2009-10-09
    Description: Relative to the present day, meridional temperature gradients in the Early Eocene age ( approximately 56-53 Myr ago) were unusually low, with slightly warmer equatorial regions but with much warmer subtropical Arctic and mid-latitude climates. By the end of the Eocene epoch ( approximately 34 Myr ago), the first major Antarctic ice sheets had appeared, suggesting that major cooling had taken place. Yet the global transition into this icehouse climate remains poorly constrained, as only a few temperature records are available portraying the Cenozoic climatic evolution of the high southern latitudes. Here we present a uniquely continuous and chronostratigraphically well-calibrated TEX(86) record of sea surface temperature (SST) from an ocean sediment core in the East Tasman Plateau (palaeolatitude approximately 65 degrees S). We show that southwest Pacific SSTs rose above present-day tropical values (to approximately 34 degrees C) during the Early Eocene age ( approximately 53 Myr ago) and had gradually decreased to about 21 degrees C by the early Late Eocene age ( approximately 36 Myr ago). Our results imply that there was almost no latitudinal SST gradient between subequatorial and subpolar regions during the Early Eocene age (55-50 Myr ago). Thereafter, the latitudinal gradient markedly increased. In theory, if Eocene cooling was largely driven by a decrease in atmospheric greenhouse gas concentration, additional processes are required to explain the relative stability of tropical SSTs given that there was more significant cooling at higher latitudes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bijl, Peter K -- Schouten, Stefan -- Sluijs, Appy -- Reichart, Gert-Jan -- Zachos, James C -- Brinkhuis, Henk -- England -- Nature. 2009 Oct 8;461(7265):776-9. doi: 10.1038/nature08399.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Palaeoecology, Institute of Environmental Biology, Faculty of Science, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands. p.k.bijl@uu.nl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19812670" target="_blank"〉PubMed〈/a〉
    Keywords: Antarctic Regions ; Biological Evolution ; Climate ; Geologic Sediments/analysis/chemistry ; History, Ancient ; Ice Cover ; Oxygen Isotopes ; Pacific Ocean ; Plankton/metabolism ; Seawater/*analysis ; *Temperature ; Water Movements
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2012-08-31
    Description: Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Palike, Heiko -- Lyle, Mitchell W -- Nishi, Hiroshi -- Raffi, Isabella -- Ridgwell, Andy -- Gamage, Kusali -- Klaus, Adam -- Acton, Gary -- Anderson, Louise -- Backman, Jan -- Baldauf, Jack -- Beltran, Catherine -- Bohaty, Steven M -- Bown, Paul -- Busch, William -- Channell, Jim E T -- Chun, Cecily O J -- Delaney, Margaret -- Dewangan, Pawan -- Dunkley Jones, Tom -- Edgar, Kirsty M -- Evans, Helen -- Fitch, Peter -- Foster, Gavin L -- Gussone, Nikolaus -- Hasegawa, Hitoshi -- Hathorne, Ed C -- Hayashi, Hiroki -- Herrle, Jens O -- Holbourn, Ann -- Hovan, Steve -- Hyeong, Kiseong -- Iijima, Koichi -- Ito, Takashi -- Kamikuri, Shin-ichi -- Kimoto, Katsunori -- Kuroda, Junichiro -- Leon-Rodriguez, Lizette -- Malinverno, Alberto -- Moore, Ted C Jr -- Murphy, Brandon H -- Murphy, Daniel P -- Nakamura, Hideto -- Ogane, Kaoru -- Ohneiser, Christian -- Richter, Carl -- Robinson, Rebecca -- Rohling, Eelco J -- Romero, Oscar -- Sawada, Ken -- Scher, Howie -- Schneider, Leah -- Sluijs, Appy -- Takata, Hiroyuki -- Tian, Jun -- Tsujimoto, Akira -- Wade, Bridget S -- Westerhold, Thomas -- Wilkens, Roy -- Williams, Trevor -- Wilson, Paul A -- Yamamoto, Yuhji -- Yamamoto, Shinya -- Yamazaki, Toshitsugu -- Zeebe, Richard E -- England -- Nature. 2012 Aug 30;488(7413):609-14. doi: 10.1038/nature11360.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton SO14 3ZH, UK. hpaelike@marum.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22932385" target="_blank"〉PubMed〈/a〉
    Keywords: *Altitude ; Atmosphere/chemistry ; Calcium Carbonate/*analysis ; *Carbon Cycle ; Carbon Dioxide/analysis ; Diatoms/metabolism ; Foraminifera/metabolism ; Geologic Sediments/chemistry ; Global Warming/history/statistics & numerical data ; History, 21st Century ; History, Ancient ; Marine Biology ; Oxygen/metabolism ; Pacific Ocean ; Seawater/*chemistry ; Temperature
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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