西风带
海洋同位素阶段
间冰期
地质学
海洋学
气候学
南半球
北半球
冰期
古生物学
作者
Qiong Chen,Xiaoqiang Yang,Yuexing Feng,Christopher J. Bae,Wang Wei,Michael K. Gagan,Jian‐xin Zhao
标识
DOI:10.1016/j.quascirev.2023.108371
摘要
Considerable ambiguity remains over the triggers for the abrupt climate deterioration that terminated the Last Interglacial Marine Isotope Stage 5e (MIS5e) period. A prevailing explanation is a sudden reduction in Atlantic Meridional Overturning Circulation (AMOC) in response to the reduced boreal summer insolation. Nonetheless, this opinion is challenged by the early weakening of the Asian summer monsoon (ASM) documented in the Chinese speleothem oxygen isotope (δ18O) ratio records. Here we propose a new mechanism involving a northerly shift of the Southern Hemisphere mid-latitude westerlies (SHW), based on saturation magnetization (Ms) and stable carbon (δ13C) and oxygen isotopes from a speleothem in northern Tasmania. The Ms record shows high-frequent peaks at 122.8–119.7 ka B.P., while δ18O and δ13C ratios first increase significantly (122.8–122.2 ka B.P.) and then decrease (122.2–119.7 ka B.P.). These Ms peaks suggest a northward shift of SHW at 122.8–119.7 ka B.P., which precedes the earliest ASM weakening for MIS5e demise and coincides with the reduced Agulhas leakage. This indicates that when SHW reaches a northerly position, the reduced Agulhas leakage leads to an anomalous warming in the southern Indian Ocean, further weakening the cross-equatorial flow. Such a process would aggravate the ASM weakening caused by the decline in boreal summer insolation and initiate an early MIS5e demise.
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