Late Holocene Indian Summer Monsoon Variation Recorded by <italic>δ</italic> <sup>13</sup>C from Peat Cellulose in Hengduan Mountain Area

<p indent="0mm">The Indian Summer Monsoon (ISM) is crucial for the livelihoods and economic development of southwestern China. Understanding the variability of the ISM since the late Holocene is essential for gaining insights into contemporary climate dynamics in the region and improving predictions for future climate change. This study focuses on a peat sediment core from Longtang in the Hengduan Mountains. By analyzing the stable carbon isotopes in α-cellulose derived from plant remains, we reconstructed a high-resolution record of ISM changes during the late Holocene. The results show a gradual weakening of the ISM intensity from –268 to <sc>1600 A.</sc>D., followed by a strengthening after <sc>1600 A.</sc>D., this trend is consistent with other records from lakes, stalagmites and peat deposits in the Indian monsoon region. Additionally, the reconstructed late Holocene ISM variations reveal centennial-scale changes superimposed on millennial-scale trends. During the Medieval Warm Period <sc>(1100-1400 A.</sc>D.), the ISM was relatively weak and the climate was drier. During the Little Ice Age <sc>(1450-1850 A.</sc>D.), it showed two distinct stages of change: the early Little Ice Age <sc>(1450-1650 A.</sc>D.), corresponding to the weakest ISM and the driest climate, and the late Little Ice Age <sc>(1650-1850 A.</sc>D.) with the ISM began to strengthen and the climate became humid. Further exploration of the driving mechanisms reveals that variations in the ISM may be influenced by Total Solar Irradiance, the Intertropical Convergence Zone, and Indo-Pacific sea surface temperatures.