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<p>The 4.2&#xa0;ka event represents the most significant climatic event during the transition from the Mid-to-Late Holocene, exerting profound impacts on regional ecosystems and human civilization development. However, debates persist regarding its influence across the monsoonal region of China, including the spatiotemporal characteristics of hydrological changes and the underlying mechanisms. Here, we present records of the Asian summer monsoon and rainfall evolution using four <sup>230</sup>Th dating results and 119 sets of δ<sup>18</sup>O and δ<sup>13</sup>C measurements on a stalagmite BL3 from Bailong Cave, Guizhou Province, southwest China. The sample grew from 5023 to 2994 a BP, with an average temporal resolution of approximately 17&#xa0;years. The speleothem δ<sup>18</sup>O is a proxy for the Asian summer monsoon intensity and partially contributed to by local rainfall changes, and δ<sup>13</sup>C reflects local vegetation regulated by rainfall changes. A comprehensive analysis of BL3 records with other high-resolution, accurately dated paleoclimate records from the monsoonal region of China indicates significant spatiotemporal discrepancies of hydrological responses to the 4.2&#xa0;ka event. Consistent aridification occurred in the north and southwest China, while humidification patterns emerged in the central and southeast China. Comparison with records of internal and external forcings suggests a multi-forcing mechanism for the spatial rainfall pattern in China during the 4.2&#xa0;ka event. Triggered by the North Atlantic Bond 3 event, the Asian summer monsoon collapsed and monsoon rainfall decreased rapidly at around 4300 a BP. The North Atlantic Bond 3 event released ice-rafted debris and weakened the Atlantic Meridional Overturning Circulation, leading to the southward shift of the Intertropical Convergence Zone, which prolonged the weak monsoon status and caused dry climate conditions in China. Meanwhile, increases in the El Niño-Southern Oscillation variability induced the westward strengthening of the Western Pacific Subtropical High, leading to the stagnation of monsoon rainfall belt and the final excessive precipitation in central and southeast regions.</p>

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The spatial rainfall pattern in China during the 4.2 ka event and its forcing mechanism

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Bin Zhao,
  • Chuntong He,
  • Jiangying Wu,
  • Yongjin Wang,
  • Kan Zhao,
  • Quan Wang,
  • Hai Cheng,
  • Yijia Liang

摘要

The 4.2 ka event represents the most significant climatic event during the transition from the Mid-to-Late Holocene, exerting profound impacts on regional ecosystems and human civilization development. However, debates persist regarding its influence across the monsoonal region of China, including the spatiotemporal characteristics of hydrological changes and the underlying mechanisms. Here, we present records of the Asian summer monsoon and rainfall evolution using four 230Th dating results and 119 sets of δ18O and δ13C measurements on a stalagmite BL3 from Bailong Cave, Guizhou Province, southwest China. The sample grew from 5023 to 2994 a BP, with an average temporal resolution of approximately 17 years. The speleothem δ18O is a proxy for the Asian summer monsoon intensity and partially contributed to by local rainfall changes, and δ13C reflects local vegetation regulated by rainfall changes. A comprehensive analysis of BL3 records with other high-resolution, accurately dated paleoclimate records from the monsoonal region of China indicates significant spatiotemporal discrepancies of hydrological responses to the 4.2 ka event. Consistent aridification occurred in the north and southwest China, while humidification patterns emerged in the central and southeast China. Comparison with records of internal and external forcings suggests a multi-forcing mechanism for the spatial rainfall pattern in China during the 4.2 ka event. Triggered by the North Atlantic Bond 3 event, the Asian summer monsoon collapsed and monsoon rainfall decreased rapidly at around 4300 a BP. The North Atlantic Bond 3 event released ice-rafted debris and weakened the Atlantic Meridional Overturning Circulation, leading to the southward shift of the Intertropical Convergence Zone, which prolonged the weak monsoon status and caused dry climate conditions in China. Meanwhile, increases in the El Niño-Southern Oscillation variability induced the westward strengthening of the Western Pacific Subtropical High, leading to the stagnation of monsoon rainfall belt and the final excessive precipitation in central and southeast regions.