Middle Miocene Ice sheet Dynamics, Deep‐Sea Temperatures, and Carbon Cycling: A Southern Ocean Perspective

Amelia E. Shevenell, James P. Kennett, David W. Lea

Research output: Contribution to journalArticlepeer-review

Abstract

<p> Relative contributions of ice volume and temperature change to the global &sim;1&permil; <em> &delta; </em> <sup> 18 </sup> O increase at &sim;14 Ma are required for understanding feedbacks involved in this major Cenozoic climate transition. A 3&hyphen;ma benthic foraminifer Mg/Ca record of Southern Ocean temperatures across the middle Miocene climate transition reveals &sim;2 &plusmn; 2&deg;C cooling (14.2&ndash;13.8 Ma), indicating that &sim;70% of the increase relates to ice growth. Seawater <em> &delta; </em> <sup> 18 </sup> O, calculated from Mg/Ca and <em> &delta; </em> <sup> 18 </sup> O, suggests that at &sim;15 Ma Antarctica's cryosphere entered an interval of apparent eccentricity&hyphen;paced expansion. Glaciations increased in intensity, revealing a central role for internal climate feedbacks. Comparison of ice volume and ocean temperature records with inferred <em> p </em> CO <sub> 2 </sub> levels indicates that middle Miocene cryosphere expansion commenced during an interval of Southern Ocean warmth and low atmospheric <em> p </em> CO <sub> 2 </sub> . The Antarctic system appears sensitive to changes in heat/moisture supply when atmospheric <em> p </em> CO <sub> 2 </sub> was low, suggesting the importance of internal feedbacks in this climate transition.</p>
Original languageAmerican English
JournalGeochemistry, Geophysics, Geosystems
Volume9
DOIs
StatePublished - Feb 1 2008
Externally publishedYes

Keywords

  • paleoceanography
  • Cenozoic climate
  • geochemistry
  • Antarctica

Disciplines

  • Life Sciences

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