Middle Miocene ice sheet dynamics, deep‐sea temperatures, and carbon cycling: A Southern Ocean perspective
Middle Miocene ice sheet dynamics, deep‐sea temperatures, and carbon cycling: A Southern Ocean perspective
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DOI：
10.1029/2007gc001736
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发表时间：
2008-02
期刊：
影响因子：
3.7
通讯作者：
A. Shevenell;J. Kennett;D. Lea
中科院分区：
文献类型：
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作者：
A. Shevenell;J. Kennett;D. Lea
冰量和温度变化对全球1014 Ma时δ 18 O增加的相对贡献是理解这一主要新生代气候转变的反馈所必需的。在中新世中期气候转变期间，南大洋温度的一个3-ma底栖有孔虫Mg/Ca记录显示，温度下降了14.2-13.8 Ma，表明70%的增加与冰的生长有关。根据Mg/Ca和δ 18 O计算的海水δ 18 O表明，在2.15 Ma时，南极洲的冰冻圈进入了一个明显的偏心率-步调膨胀的区间。冰川的强度增加，揭示了内部气候反馈的核心作用。冰量和海洋温度记录与推断的二氧化碳分压水平的比较表明，中中新世冰冻圈扩张开始在南大洋温暖和低大气二氧化碳分压的间隔。南极系统出现敏感的热/水分供应的变化时，大气pCO 2是低的，这表明在这种气候转变的内部反馈的重要性。
Relative contributions of ice volume and temperature change to the global ∼1‰ δ18O 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 δ18O, calculated from Mg/Ca and δ18O, 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.