The Role of Carbon Dioxide During the Onset of Antarctic Glaciation

  title={The Role of Carbon Dioxide During the Onset of Antarctic Glaciation},
  author={Mark Pagani and Matthew Huber and Zhonghui Liu and Steven M. Bohaty and Jorijntje Henderiks and Willem P. Sijp and Srinath Krishnan and Robert M. DeConto},
  pages={1261 - 1264}
Antarctica glaciation began soon after a large decrease in the concentration of atmospheric carbon dioxide around 35 million years ago. Earth’s modern climate, characterized by polar ice sheets and large equator-to-pole temperature gradients, is rooted in environmental changes that promoted Antarctic glaciation ~33.7 million years ago. Onset of Antarctic glaciation reflects a critical tipping point for Earth’s climate and provides a framework for investigating the role of atmospheric carbon… 
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[1] Growth of Antarctic ice sheet during the Cenozoic 34 million years ago appears as a potential tipping point in the long term cooling trend that began 50 Ma ago. For decades, the onset of the
Palaeoclimate science: Causes and effects of Antarctic ice
  • D. Lunt
  • Environmental Science, Geography
  • 2014
A climate model is used to show that the growth of the ice sheet — forced by changes in CO2 — drove the changes in ocean circulation, in contrast to the opening of the gateways, which had relatively little impact on ocean circulation.
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In this simulation, declining Cenozoic CO2 first leads to the formation of small, highly dynamic ice caps on high Antarctic plateaux, and at a later time, a CO2 threshold is crossed, initiating ice-sheet height/mass-balance feedbacks that cause the ice caps to expand rapidly with large orbital variations, eventually coalescing into a continental-scale East Antarctic Ice Sheet.
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About 34 million years ago, Earth's climate shifted from a relatively ice-free world to one with glacial conditions on Antarctica characterized by substantial ice sheets. How Earth's temperature
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Stable carbon isotopic values of di-unsaturated alkenones extracted from deep sea cores are used to reconstruct pCO2 from the middle Eocene to the late Oligocene and demonstrate that it ranged between 1000 to 1500 parts per million by volume in the middle to late Eocene, then decreased in several steps during theOligocene, and reached modern levels by the latest Oligaen.
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The changes in oxygen-isotope composition across the Eocene/Oligocene boundary are too large to be explained by Antarctic ice-sheet growth alone and must therefore also indicate contemporaneous global cooling and/or Northern Hemisphere glaciation.
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[1] Near the Eocene's close (∼34 million years ago), the climate system underwent one of the largest shifts in Earth's history: Antarctic terrestrial ice sheets suddenly grew and ocean productivity
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It appears that vast amounts of CO2 were injected into the atmosphere, and a sea surface temperature increase of as much a 6°C accompanied the atmospheric CO2 rise, suggesting that elevated pCO2 played a major role in global warming during the MECO.