Zhang Zeke, Liu Zhengyu, Li Gaojun, Cai Yanjun, Wen Qin, Cheng Hai, Lawrence Edwards R, Lei Jing, Liu Heng, Jing Zhaowei, Li Tao, Clemens Steven C, Wang Yongjin, Sun Youbin, Shi Zhengguo, Tan Liangcheng, Kang Shugang, Wang Xulong, Jin Zhangdong, Zhou Weijian, An Zhisheng
State Key Laboratory of Loess Science, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China.
Ministry of Education Key Laboratory of Surficial Geochemistry, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China.
Proc Natl Acad Sci U S A. 2025 Jul 15;122(28):e2425565122. doi: 10.1073/pnas.2425565122. Epub 2025 Jul 11.
Speleothem δO records from central southern China have long been regarded as a key benchmark for Asian summer monsoon intensity. However, the similar δO minima observed among precession minima and their link to seasonal precipitation mixing remains unclear. Here, we present a 400,000-y record of summer precipitation δO from loess microcodium, which captures distinct precession cycles similar to those seen in speleothem δO records, particularly during glacial periods. Notably, our microcodium δO record reveals very low-δO values during precession minima at peak interglacials, a feature absent in speleothem δO records from central southern China. This discrepancy suggests that the mixed summer and nonsummer climatic signals substantially influence the speleothem δO records from central southern China. Proxy-model comparisons indicate that the lack of very low-δO values in speleothem δO records is due to an attenuated summer signal contribution, resulting from a lower summer-to-annual precipitation ratio in southern China at strong monsoon intervals. Our findings offer a potential explanation for the long-standing puzzle of the absence of 100- and 41-kyr cycles in speleothem δO records and underscore the critical role of seasonality in interpreting paleoclimatic proxies in central southern China. These insights also have broader implications for interpreting speleothem δO records globally, advocating for a more multiseason interpretive framework.
中国中南部的洞穴石笋δO记录长期以来一直被视为亚洲夏季风强度的关键基准。然而，岁差最小值期间观测到的类似δO最小值及其与季节性降水混合的联系仍不清楚。在此，我们展示了一份来自黄土微晶的40万年夏季降水δO记录，它捕捉到了与洞穴石笋δO记录中类似的不同岁差周期，特别是在冰期期间。值得注意的是，我们的微晶δO记录揭示了在间冰期峰值的岁差最小值期间非常低的δO值，这是中国中南部洞穴石笋δO记录中所没有的特征。这种差异表明，夏季和非夏季混合气候信号对中国中南部洞穴石笋δO记录有很大影响。代理模型比较表明，洞穴石笋δO记录中缺乏非常低的δO值是由于夏季信号贡献减弱，这是由于中国南部在强季风间隔期夏季降水与年降水量的比率较低所致。我们的研究结果为洞穴石笋δO记录中缺乏10万年和4.1万年周期这一长期存在的谜题提供了一个潜在的解释，并强调了季节性在中国中南部古气候代理指标解释中的关键作用。这些见解对于全球洞穴石笋δO记录的解释也有更广泛的意义，倡导采用更具多季节的解释框架。
