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<p>A thorough understanding of the variability and forcing mechanisms driving the Indian summer monsoon (ISM), a critical climate system supporting directly over a billion people, is required to improve climate change projections and mitigate risks associated with abrupt monsoon shifts. However, millennial-scale ISM forcing and variability remain debated. Here, we present a high-resolution precipitation record reconstructed from geochemical elements of a well-dated peat core from the Huangcaoba (HCB) peatland in Yunnan Province, southwestern China, that reflects ISM variability during the Holocene. Principal component analysis (PCA) reveals that PC1, dominated by titanium (Ti), reliably reflects ISM precipitation variability. We identified eight distinct ISM weakening events at approximately 8.2, 7.5, 6.6, 6.0, 3.9, 3.0, 2.3, and 1.7 kyr BP, with the 6.0 kyr event being the most pronounced and prolonged. Our findings suggest that an ISM maximum likely commenced in the early Holocene and terminated at around 6.0 kyr BP, during which temperature and precipitation became decoupled due to internal Earth system feedback. Generally, this ISM variability was controlled by the decrease in summer insolation and southward migration of intertropical convergence zone (ITCZ) on the orbital scale. On the millennial scale, the ISM was mainly driven by high-latitude climate process, and the ice-rafted debris (IRD) events likely played a key role.</p>

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A weakened Indian summer monsoon at 6.0 kyr BP: evidence from low-latitude alpine peat, southwestern China

  • 期刊论文

  • 发表日期：

    2026年2月24日

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  • Binxu Liu,
  • Jia Liu,
  • Xingyuan Qin,
  • Jiaxi Zhou,
  • Shufeng Li,
  • Tao Su

摘要

A thorough understanding of the variability and forcing mechanisms driving the Indian summer monsoon (ISM), a critical climate system supporting directly over a billion people, is required to improve climate change projections and mitigate risks associated with abrupt monsoon shifts. However, millennial-scale ISM forcing and variability remain debated. Here, we present a high-resolution precipitation record reconstructed from geochemical elements of a well-dated peat core from the Huangcaoba (HCB) peatland in Yunnan Province, southwestern China, that reflects ISM variability during the Holocene. Principal component analysis (PCA) reveals that PC1, dominated by titanium (Ti), reliably reflects ISM precipitation variability. We identified eight distinct ISM weakening events at approximately 8.2, 7.5, 6.6, 6.0, 3.9, 3.0, 2.3, and 1.7 kyr BP, with the 6.0 kyr event being the most pronounced and prolonged. Our findings suggest that an ISM maximum likely commenced in the early Holocene and terminated at around 6.0 kyr BP, during which temperature and precipitation became decoupled due to internal Earth system feedback. Generally, this ISM variability was controlled by the decrease in summer insolation and southward migration of intertropical convergence zone (ITCZ) on the orbital scale. On the millennial scale, the ISM was mainly driven by high-latitude climate process, and the ice-rafted debris (IRD) events likely played a key role.