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Publication Detail
Middle Miocene ice sheet dynamics, deep-sea temperatures, and carbon cycling: A Southern Ocean perspective
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Article
  • Authors:
    Shevenell AE, Kennett JP, Lea DW
  • Publisher:
    AMER GEOPHYSICAL UNION
  • Publication date:
    09/02/2008
  • Journal:
    GEOCHEM GEOPHY GEOSY
  • Volume:
    9
  • Print ISSN:
    1525-2027
  • Language:
    EN
  • Keywords:
    paleoceanography, Cenozoic climate, geochemistry, Antarctica, BENTHIC FORAMINIFERAL MG/CA, CLIMATE-CHANGE, SURFACE TEMPERATURE, DIOXIDE, EVOLUTION, RECORD, PALEOTHERMOMETRY, CIRCULATION, GLACIATION, HYPOTHESIS
  • Addresses:
    Shevenell, AE
    Univ Washington
    Sch Oceanog
    Seattle
    WA
    98195
    USA
Abstract
Relative contributions of ice volume and temperature change to the global similar to 1 parts per thousand delta O-18 increase at similar to 14 Ma are required for understanding feedbacks involved in this major Cenozoic climate transition. A 3-ma benthic foraminifer Mg/Ca record of Southern Ocean temperatures across the middle Miocene climate transition reveals similar to 2 +/- 2 degrees C cooling (14.2-13.8 Ma), indicating that similar to 70% of the increase relates to ice growth. Seawater delta O-18, calculated from Mg/Ca and delta O-18, suggests that at similar to 15 Ma Antarctica's cryosphere entered an interval of apparent eccentricity-paced expansion. Glaciations increased in intensity, revealing a central role for internal climate feedbacks. Comparison of ice volume and ocean temperature records with inferred pCO(2) levels indicates that middle Miocene cryosphere expansion commenced during an interval of Southern Ocean warmth and low atmospheric pCO(2). The Antarctic system appears sensitive to changes in heat/moisture supply when atmospheric pCO(2) was low, suggesting the importance of internal feedbacks in this climate transition.
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