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<p>The Indian summer monsoon (ISM) is a major component of the Asian monsoon system, and exerts a critical influence on regional climate variability. However, continuous, high-resolution paleoclimate records spanning a full glacial-interglacial cycle remain limited, constraining our understanding of the ISM dynamics across different timescales. In this study, we reconstruct ISM variability from 184 − 25&#xa0;ka using geochemical and environmental magnetic proxies from a lacustrine sediment core in the Heqing Basin, Southwest China. Rock magnetic results indicate that higher concentration-dependent magnetic parameters (χ, ARM, SIRM) occur during weaker monsoon (drier) phases, whereas lower values reflect stronger monsoon (wetter) phases. The proxy records reveal a pronounced dry-wet cycle throughout 184 − 25&#xa0;ka: Phase I (184 − 131&#xa0;ka) featured relatively weak ISM intensity and drier conditions; Phase II (131 − 69&#xa0;ka) saw an overall increase in ISM intensity accompanied by higher rainfall; Phase III (69 − 57&#xa0;ka) reverted to arid conditions; Phase IV (57 − 25&#xa0;ka) exhibited a generally wetter climate, though punctuated by frequent major drought events. On glacial-interglacial timescales, ISM variability was primarily paced by Northern Hemisphere summer insolation (NHSI). On millennial timescales, the ISM weakened during ~ 57 − 25&#xa0;ka (Phase IV, MIS 3). Weak ISM, as indicated by proxies in the PT2 core, showed consistent variations with Atlantic meridional overturning circulation (AMOC) weakening, as indicated by ²³¹Pa/²³⁰Th, and with low-latitude monsoon circulation. This pattern suggests that the region was jointly controlled by high-latitude boundary conditions and tropical ocean-atmosphere coupling processes. Therefore, variations in the ISM across different timescales are driven by multiple factors rather than solely by solar radiation.</p>

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Indian summer monsoon variability from 184 to 25 ka inferred from sedimentary magnetic properties in Heqing Basin, Southwest China

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  • 发表日期：

    2025年12月5日

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  • Ziyi Yang,
  • Xinwen Xu,
  • Shuheng Li,
  • Xiaoke Qiang

摘要

The Indian summer monsoon (ISM) is a major component of the Asian monsoon system, and exerts a critical influence on regional climate variability. However, continuous, high-resolution paleoclimate records spanning a full glacial-interglacial cycle remain limited, constraining our understanding of the ISM dynamics across different timescales. In this study, we reconstruct ISM variability from 184 − 25 ka using geochemical and environmental magnetic proxies from a lacustrine sediment core in the Heqing Basin, Southwest China. Rock magnetic results indicate that higher concentration-dependent magnetic parameters (χ, ARM, SIRM) occur during weaker monsoon (drier) phases, whereas lower values reflect stronger monsoon (wetter) phases. The proxy records reveal a pronounced dry-wet cycle throughout 184 − 25 ka: Phase I (184 − 131 ka) featured relatively weak ISM intensity and drier conditions; Phase II (131 − 69 ka) saw an overall increase in ISM intensity accompanied by higher rainfall; Phase III (69 − 57 ka) reverted to arid conditions; Phase IV (57 − 25 ka) exhibited a generally wetter climate, though punctuated by frequent major drought events. On glacial-interglacial timescales, ISM variability was primarily paced by Northern Hemisphere summer insolation (NHSI). On millennial timescales, the ISM weakened during ~ 57 − 25 ka (Phase IV, MIS 3). Weak ISM, as indicated by proxies in the PT2 core, showed consistent variations with Atlantic meridional overturning circulation (AMOC) weakening, as indicated by ²³¹Pa/²³⁰Th, and with low-latitude monsoon circulation. This pattern suggests that the region was jointly controlled by high-latitude boundary conditions and tropical ocean-atmosphere coupling processes. Therefore, variations in the ISM across different timescales are driven by multiple factors rather than solely by solar radiation.