The evolution of the Indian Summer Monsoon (ISM) has been widely investigated and traditionally interpreted as consequences of orbital forcing change and the migration of the Intertropical Convergent Zone (ITCZ). The potential influence of sea-surface temperature (SST) on ISM variation at millennial time scales has been progressively proposed in recent studies. Towards a better understanding of Holocene evolution of ISM, especially the potential response to variations in SST, a 643 cm continuous sediment sequence covering the past 11.1 ka was recovered from Beihai Wetland in western Yunnan Plateau. Fossil pollen analysis revealed that evergreen broadleaved forest dominated the regional vegetation in the early Holocene, which represented a warm and humid period associated with strong ISM. Expansions of deciduous broadleaved forest and grassland from 5.2 cal. ka BP to the present, together with the appearance of abundant plant remains, indicate the formation of the wetland system. Ordination analysis of the pollen assemblages further confirmed the abrupt vegetation turnover at ca. 5.2 cal. ka BP, which is consistent with the abrupt decline in reconstructed mean annual precipitation (P_ann, from ca. 1400 to 1100 mm), and indicates an abrupt decline in the summer monsoon. We performed a climate regime shift test on various records from the ISM domain and eastern Africa and found this phenomenon as well, which could not be explained by changes in solar insolation or the migration of the ITCZ. A mid-Holocene cooling was detected from the Indian Ocean, especially a decreased SST in the tropical Indian Ocean ca. 5.5 cal. ka BP. Cooling of the tropical Indian Ocean possibly caused the abrupt retreat of the summer monsoon by restraining the duration of the monsoonal season and the convergent process, which was supported by an abrupt monsoon decline based on results from a minimal concept model.

印度夏季风（ISM）的演变已得到广泛研究，传统上将其解释为轨道强迫变化和热带辐合带（ITCZ）迁移的结果。最近的研究逐渐提出了海表温度（SST）对千禧年尺度上ISM变化的潜在影响。为了更好地了解ISM全新世演化，特别是对SST变化的潜在响应，从滇西高原的北海湿地回收了一个643 cm的连续沉积序列，覆盖了过去的11.1 ka。化石花粉分析表明，全新世初期常绿阔叶林主导着该地区的植被，这代表了强烈的ISM的温暖湿润时期。5.2 cal。起的落叶阔叶林和草原的扩张。ka BP到现在，以及大量植物残留物的出现，表明了湿地系统的形成。对花粉组合的排序分析进一步证实了大约在2000年突然的植被更新。5.2卡路里 ka BP，与重建的平均年降水量突然下降（P_安，从约 1400至1100毫米），表示夏季风突然下降。我们对ISM领域和东非的各种记录进行了气候变化试验，结果也发现了这一现象，这不能用日照强度的变化或ITCZ的迁移来解释。在印度洋发现了全新世中期的冷却，尤其是热带印度洋的SST降低。5.5卡路里 ka BP。热带印度洋的降温可能会通过限制季风季节的持续时间和收敛过程而导致夏季风的突然退缩，这得益于基于最小概念模型结果的季风突然下降。