中期米奥森南大洋冷却和南极冰层扩张
Amelia E Shevenell1, James P Kennett, David W Lea
1Department of Geological Sciences and Marine Science Institute, University of California, Santa Barbara, CA 93106-9630, USA. ashevenell@umail.ucsb.edu
概括
中米奥森气候转型在西南太平洋出现了显著的降温,这是由于海洋循环的变化,而不是二氧化碳的减少. 这种冷却在南极冰川扩张之前发生,揭示了复杂的气候反.
科学领域:
- 古代海洋学 古代海洋学 古代海洋学
- 气候科学 气候科学
- 海洋地质 海洋地质学
背景情况:
- 中米欧纪气候过渡 (14.213.8亿年前) 是全球冷却的关键时期.
- 以前的假设表明大气中的二氧化碳 (CO2) 吸收是这种转变的主要驱动因素.
- 了解轨道强迫,海洋循环和冰层膨胀的相互作用是重建过去气候动态的关键.
研究的目的:
- 为了重建中米欧纪气候过渡期间的高度海面温度 (SSTs).
- 调查南大洋冷却和南极冰层扩张的驱动因素.
- 挑战或支持有关二氧化碳减排在纪气候变化中的作用的现有假设.
主要方法:
- 在南大洋浮游生物中分析/的比率,以确定古气温.
- 重建的SSTs与全球碳循环代理和冰体积趋势的比较.
- 评估轨道 (离心率) 强迫对气候变异性的影响.
主要成果:
- 高度西南太平洋SSTs在中米欧纪气候过渡期间冷却67°C.
- 渐进的冷却与偏心强迫相伴,发生在南极冰层扩张前大约6万年.
- 证据表明,海洋循环的变化,而不是偶尔的二氧化碳吸收,启动了冷却和冰的增长.
结论:
- 海洋循环的轨道节奏变化显著改变了午线热量和蒸汽传输.
- 这些循环转移引发了南极冰的增长和随后的全球降温,挑战了二氧化碳减排假设.
- 这些发现凸显了海洋-大气-冰反对于在低大气二氧化碳期间调节气候的重要性.
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