Methane, Monsoons, and Modulation of Millennial‐Scale Climate
Methane, Monsoons, and Modulation of Millennial‐Scale Climate
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DOI：
10.1029/2020gl087613
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发表时间：
2020-04
影响因子：
5.2
通讯作者：
K. Thirumalai;S. Clemens;J. Partin
中科院分区：
文献类型：
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作者：
K. Thirumalai;S. Clemens;J. Partin
地球轨道的几何形状通过调节入射太阳辐射的变化对气候产生深远影响。更新世记录与轨道节奏的气候变化相叠加，揭示了以突变和快速波动为特征的千年尺度变化。然而，轨道强迫在多大程度上调节这些千年变化的幅度和时间尚不清楚。在这里，我们在两个较好的记录中分离出千年尺度变化（MMV）的大小，这两个记录都与岁差周期（19，000年和23，000年的周期）有关：中国洞穴堆积物δ 18 O，通常被解释为亚洲季风强度的代理，以及大气甲烷。在千年时间尺度（1，000 - 10，000年），我们发现了一个基本的解耦，其中岁差直接调制甲烷的MMV，但不调制洞穴沉积物δ 18 O的MMV，这与南极冰芯δ 2 H的MMV惊人地相似。一种解释是甲烷的MMV响应于中纬度到高纬度日照的变化，而洞穴沉积物δ 18 O则受到内部气候反馈的调制。
Earth's orbital geometry exerts a profound influence on climate by regulating changes in incoming solar radiation. Superimposed on orbitally paced climate change, Pleistocene records reveal substantial millennial‐scale variability characterized by abrupt changes and rapid swings. However, the extent to which orbital forcing modulates the amplitude and timing of these millennial variations is unclear. Here we isolate the magnitude of millennial‐scale variability (MMV) in two well‐dated records, both linked to precession cycles (19,000‐ and 23,000‐year periodicity): composite Chinese speleothem δ18O, commonly interpreted as a proxy for Asian monsoon intensity, and atmospheric methane. At the millennial timescale (1,000–10,000 years), we find a fundamental decoupling wherein precession directly modulates the MMV of methane but not that of speleothem δ18O, which is shown to be strikingly similar to the MMV of Antarctic ice core δ2H. One explanation is that the MMV of methane responds to changes in midlatitude to high‐latitude insolation, whereas speleothem δ18O is modulated by internal climate feedbacks.