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Middle Miocene ice sheet dynamics, deep-sea temperatures, and carbon cycling: A Southern Ocean perspective
Geological Sciences and Marine Science Institute, University of California, Santa Barbara, Santa Barbara, California 93106, USA
Geological Sciences and Marine Science Institute, University of California, Santa Barbara, Santa Barbara, California 93106, USA
Geological Sciences and Marine Science Institute, University of California, Santa Barbara, Santa Barbara, California 93106, USA
Relative contributions of ice volume and temperature change to the global ∼1‰ δ 18O 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 δ 18O, calculated from Mg/Ca and δ 18O, 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 pCO2 levels indicates that middle Miocene cryosphere expansion commenced during an interval of Southern Ocean warmth and low atmospheric pCO2. The Antarctic system appears sensitive to changes in heat/moisture supply when atmospheric pCO2 was low, suggesting the importance of internal feedbacks in this climate transition.
Received 25 June 2007; accepted 7 November 2007; published 9 February 2008.
Citation: (2008), Middle Miocene ice sheet dynamics, deep-sea temperatures, and carbon cycling: A Southern Ocean perspective, Geochem. Geophys. Geosyst., 9, Q02006, doi:10.1029/2007GC001736.
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