Abstract
<p> Relative contributions of ice volume and temperature change to the global ∼1‰ <em> δ </em> <sup> 18 </sup> O increase at ∼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 ∼2 ± 2°C cooling (14.2–13.8 Ma), indicating that ∼70% of the increase relates to ice growth. Seawater <em> δ </em> <sup> 18 </sup> O, calculated from Mg/Ca and <em> δ </em> <sup> 18 </sup> O, suggests that at ∼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 <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 language | American English |
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Journal | Geochemistry, Geophysics, Geosystems |
Volume | 9 |
DOIs | |
State | Published - Feb 1 2008 |
Externally published | Yes |
Keywords
- paleoceanography
- Cenozoic climate
- geochemistry
- Antarctica
Disciplines
- Life Sciences