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  • 1
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    Past extreme warming events linked to massive carbon release from thawing permafrost (2012)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2012-04-07
    Description: Between about 55.5 and 52 million years ago, Earth experienced a series of sudden and extreme global warming events (hyperthermals) superimposed on a long-term warming trend. The first and largest of these events, the Palaeocene-Eocene Thermal Maximum (PETM), is characterized by a massive input of carbon, ocean acidification and an increase in global temperature of about 5 degrees C within a few thousand years. Although various explanations for the PETM have been proposed, a satisfactory model that accounts for the source, magnitude and timing of carbon release at the PETM and successive hyperthermals remains elusive. Here we use a new astronomically calibrated cyclostratigraphic record from central Italy to show that the Early Eocene hyperthermals occurred during orbits with a combination of high eccentricity and high obliquity. Corresponding climate-ecosystem-soil simulations accounting for rising concentrations of background greenhouse gases and orbital forcing show that the magnitude and timing of the PETM and subsequent hyperthermals can be explained by the orbitally triggered decomposition of soil organic carbon in circum-Arctic and Antarctic terrestrial permafrost. This massive carbon reservoir had the potential to repeatedly release thousands of petagrams (10(15) grams) of carbon to the atmosphere-ocean system, once a long-term warming threshold had been reached just before the PETM. Replenishment of permafrost soil carbon stocks following peak warming probably contributed to the rapid recovery from each event, while providing a sensitive carbon reservoir for the next hyperthermal. As background temperatures continued to rise following the PETM, the areal extent of permafrost steadily declined, resulting in an incrementally smaller available carbon pool and smaller hyperthermals at each successive orbital forcing maximum. A mechanism linking Earth's orbital properties with release of soil carbon from permafrost provides a unifying model accounting for the salient features of the hyperthermals.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉DeConto, Robert M -- Galeotti, Simone -- Pagani, Mark -- Tracy, David -- Schaefer, Kevin -- Zhang, Tingjun -- Pollard, David -- Beerling, David J -- England -- Nature. 2012 Apr 4;484(7392):87-91. doi: 10.1038/nature10929.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01002, USA. deconto@geo.umass.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22481362" target="_blank"〉PubMed〈/a〉
    Keywords: Antarctic Regions ; Arctic Regions ; Atmosphere/chemistry ; Calibration ; Carbon/*analysis ; Carbon Cycle ; Ecosystem ; Feedback ; *Freezing ; Global Warming/*history ; Greenhouse Effect/*history ; History, Ancient ; Italy ; Models, Theoretical ; Seawater/chemistry ; Soil/*chemistry ; *Temperature
    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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    2.8 million years of Arctic climate change from Lake El'gygytgyn, NE Russia (2012)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2012-06-23
    Description: The reliability of Arctic climate predictions is currently hampered by insufficient knowledge of natural climate variability in the past. A sediment core from Lake El'gygytgyn in northeastern (NE) Russia provides a continuous, high-resolution record from the Arctic, spanning the past 2.8 million years. This core reveals numerous "super interglacials" during the Quaternary; for marine benthic isotope stages (MIS) 11c and 31, maximum summer temperatures and annual precipitation values are ~4 degrees to 5 degrees C and ~300 millimeters higher than those of MIS 1 and 5e. Climate simulations show that these extreme warm conditions are difficult to explain with greenhouse gas and astronomical forcing alone, implying the importance of amplifying feedbacks and far field influences. The timing of Arctic warming relative to West Antarctic Ice Sheet retreats implies strong interhemispheric climate connectivity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Melles, Martin -- Brigham-Grette, Julie -- Minyuk, Pavel S -- Nowaczyk, Norbert R -- Wennrich, Volker -- DeConto, Robert M -- Anderson, Patricia M -- Andreev, Andrei A -- Coletti, Anthony -- Cook, Timothy L -- Haltia-Hovi, Eeva -- Kukkonen, Maaret -- Lozhkin, Anatoli V -- Rosen, Peter -- Tarasov, Pavel -- Vogel, Hendrik -- Wagner, Bernd -- New York, N.Y. -- Science. 2012 Jul 20;337(6092):315-20. doi: 10.1126/science.1222135. Epub 2012 Jun 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Geology and Mineralogy, University of Cologne, Zuelpicher Strasse 49a, D-50674 Cologne, Germany. mmelles@uni-koeln.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22722254" target="_blank"〉PubMed〈/a〉
    Keywords: Arctic Regions ; *Climate Change ; *Cold Climate ; Geologic Sediments ; Ice Cover ; *Lakes ; Radiometric Dating ; Russia ; Time Factors
    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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