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  • Antarctic Regions  (2)
  • *Cold Climate  (1)
  • *Oceans and Seas  (1)
  • *Temperature  (1)
  • 1
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    Evidence for middle Eocene Arctic sea ice from diatoms and ice-rafted debris (2009)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2009-07-17
    Description: Oceanic sediments from long cores drilled on the Lomonosov ridge, in the central Arctic, contain ice-rafted debris (IRD) back to the middle Eocene epoch, prompting recent suggestions that ice appeared in the Arctic about 46 million years (Myr) ago. However, because IRD can be transported by icebergs (derived from land-based ice) and also by sea ice, IRD records are restricted to providing a history of general ice-rafting only. It is critical to differentiate sea ice from glacial (land-based) ice as climate feedback mechanisms vary and global impacts differ between these systems: sea ice directly affects ocean-atmosphere exchanges, whereas land-based ice affects sea level and consequently ocean acidity. An earlier report assumed that sea ice was prevalent in the middle Eocene Arctic on the basis of IRD, and although somewhat preliminary supportive evidence exists, these data are neither comprehensive nor quantified. Here we show the presence of middle Eocene Arctic sea ice from an extraordinary abundance of a group of sea-ice-dependent fossil diatoms (Synedropsis spp.). Analysis of quartz grain textural characteristics further supports sea ice as the dominant transporter of IRD at this time. Together with new information on cosmopolitan diatoms and existing IRD records, our data strongly suggest a two-phase establishment of sea ice: initial episodic formation in marginal shelf areas approximately 47.5 Myr ago, followed approximately 0.5 Myr later by the onset of seasonally paced sea-ice formation in offshore areas of the central Arctic. Our data establish a 2-Myr record of sea ice, documenting the transition from a warm, ice-free environment to one dominated by winter sea ice at the start of the middle Eocene climatic cooling phase.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stickley, Catherine E -- St John, Kristen -- Koc, Nalan -- Jordan, Richard W -- Passchier, Sandra -- Pearce, Richard B -- Kearns, Lance E -- England -- Nature. 2009 Jul 16;460(7253):376-9. doi: 10.1038/nature08163.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉[1] Department of Geology, University of Tromso, N-9037 Tromso, Norway [2] Norwegian Polar Institute, Polar Environmental Centre, N-9296 Tromso, Norway.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19606146" target="_blank"〉PubMed〈/a〉
    Keywords: Arctic Regions ; *Cold Climate ; Diatoms/chemistry/*isolation & purification/ultrastructure ; Fossils ; Geologic Sediments/microbiology ; History, Ancient ; Hydrogen-Ion Concentration ; Ice Cover/*chemistry/*microbiology ; Microscopy, Electron, Scanning ; Oceans and Seas ; Principal Component Analysis ; Salinity ; Seawater/chemistry ; Silicon Dioxide/analysis
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch (2012)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2012-08-04
    Description: The warmest global climates of the past 65 million years occurred during the early Eocene epoch (about 55 to 48 million years ago), when the Equator-to-pole temperature gradients were much smaller than today and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume. Recently the early Eocene has received considerable interest because it may provide insight into the response of Earth's climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future as a consequence of unabated anthropogenic carbon emissions. Climatic conditions of the early Eocene 'greenhouse world', however, are poorly constrained in critical regions, particularly Antarctica. Here we present a well-dated record of early Eocene climate on Antarctica from an ocean sediment core recovered off the Wilkes Land coast of East Antarctica. The information from biotic climate proxies (pollen and spores) and independent organic geochemical climate proxies (indices based on branched tetraether lipids) yields quantitative, seasonal temperature reconstructions for the early Eocene greenhouse world on Antarctica. We show that the climate in lowland settings along the Wilkes Land coast (at a palaeolatitude of about 70 degrees south) supported the growth of highly diverse, near-tropical forests characterized by mesothermal to megathermal floral elements including palms and Bombacoideae. Notably, winters were extremely mild (warmer than 10 degrees C) and essentially frost-free despite polar darkness, which provides a critical new constraint for the validation of climate models and for understanding the response of high-latitude terrestrial ecosystems to increased carbon dioxide forcing.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pross, Jorg -- Contreras, Lineth -- Bijl, Peter K -- Greenwood, David R -- Bohaty, Steven M -- Schouten, Stefan -- Bendle, James A -- Rohl, Ursula -- Tauxe, Lisa -- Raine, J Ian -- Huck, Claire E -- van de Flierdt, Tina -- Jamieson, Stewart S R -- Stickley, Catherine E -- van de Schootbrugge, Bas -- Escutia, Carlota -- Brinkhuis, Henk -- Integrated Ocean Drilling Program Expedition 318 Scientists -- England -- Nature. 2012 Aug 2;488(7409):73-7. doi: 10.1038/nature11300.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Paleoenvironmental Dynamics Group, Institute of Geosciences, Goethe University Frankfurt, Altenhoferallee 1, 60438 Frankfurt, Germany. joerg.pross@em.uni-frankfurt.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22859204" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antarctic Regions ; Atmosphere/chemistry ; Carbon Dioxide/analysis ; Cell Respiration ; Ecosystem ; Geologic Sediments/chemistry ; Greenhouse Effect/*history ; History, Ancient ; Human Activities ; Lipids/analysis ; Models, Theoretical ; Photosynthesis ; Pollen ; Reproducibility of Results ; Seasons ; Spores/isolation & purification ; *Temperature ; Trees/growth & development ; *Tropical Climate
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Reorganization of Southern Ocean plankton ecosystem at the onset of Antarctic glaciation (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-04-20
    Description: The circum-Antarctic Southern Ocean is an important region for global marine food webs and carbon cycling because of sea-ice formation and its unique plankton ecosystem. However, the mechanisms underlying the installation of this distinct ecosystem and the geological timing of its development remain unknown. Here, we show, on the basis of fossil marine dinoflagellate cyst records, that a major restructuring of the Southern Ocean plankton ecosystem occurred abruptly and concomitant with the first major Antarctic glaciation in the earliest Oligocene (~33.6 million years ago). This turnover marks a regime shift in zooplankton-phytoplankton interactions and community structure, which indicates the appearance of eutrophic and seasonally productive environments on the Antarctic margin. We conclude that earliest Oligocene cooling, ice-sheet expansion, and subsequent sea-ice formation were important drivers of biotic evolution in the Southern Ocean.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Houben, Alexander J P -- Bijl, Peter K -- Pross, Jorg -- Bohaty, Steven M -- Passchier, Sandra -- Stickley, Catherine E -- Rohl, Ursula -- Sugisaki, Saiko -- Tauxe, Lisa -- van de Flierdt, Tina -- Olney, Matthew -- Sangiorgi, Francesca -- Sluijs, Appy -- Escutia, Carlota -- Brinkhuis, Henk -- Expedition 318 Scientists -- Dotti, Carlota Escutia -- Klaus, Adam -- Fehr, Annick -- Williams, Trevor -- Bendle, James A P -- Carr, Stephanie A -- Dunbar, Robert B -- Flores, Jose-Abel -- Gonzalez, Jhon J -- Hayden, Travis G -- Iwai, Masao -- Jimenez-Espejo, Francisco J -- Katsuki, Kota -- Kong, Gee Soo -- McKay, Robert M -- Nakai, Mutsumi -- Pekar, Stephen F -- Riesselman, Christina -- Sakai, Toyosaburo -- Salzmann, Ulrich -- Shrivastava, Prakash K -- Tuo, Shouting -- Welsh, Kevin -- Yamane, Masako -- New York, N.Y. -- Science. 2013 Apr 19;340(6130):341-4. doi: 10.1126/science.1223646.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, Laboratory of Palaeobotany and Palynology, Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands. Alexander.Houben@TNO.nl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23599491" target="_blank"〉PubMed〈/a〉
    Keywords: *Adaptation, Physiological ; Animals ; Antarctic Regions ; Cold Temperature ; Dinoflagellida/*physiology ; *Ecosystem ; Fossils ; *Ice Cover ; *Oceans and Seas ; Phytoplankton/*physiology ; Zooplankton/*physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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