Stalagmite records reveal multi-scale climate oscillations of the Early Holocene Asian Summer Monsoon

Based on 7 230Th ages and 784 δ18O data from a stalagmite in Yongxing Cave, Hubei Province, this research reconstructs an Asian Summer Monsoon (ASM) evolution sequence from 11.95 to 9.98 ka B.P. with an average resolution of 3 years. The research reveals that the long-term trend of the monsoon is controlled by summer solar insolation at 65° N. Based on the mean δ18O values of stalagmite YX150b, the record is roughly divided into four stages, with mean δ18O values of -7.78‰, -8.68‰, -9.31‰, and -9.72‰. The progressive decrease in these mean values reflects a stepwise pattern during the overall negative shift of δ18O, which we describe as a "stepwise ASM intensification" structure. This ASM change is also observed in contemporaneous stalagmite δ18O records from Dongge Cave, Yamen Cave, Zhuliuping Cave and Luoshui Cave. Although the timing and magnitude of the transitions vary, the stepwise ASM change is broadly consistent. By comparing with several global records, we propose that the phased changes in the Atlantic Meridional Overturning Circulation (AMOC) along with the northward migration of the Intertropical Convergence Zone (ITCZ), were the primary drivers of this stepwise ASM change. Furthermore, this ASM change was also evident in stalagmite records from the T-Ⅱ (Ice age termination Ⅱ)、T-Ⅲ、T-Ⅳ periods, suggesting that stepwise intensification might be a common mode of ASM evolution under conditions of rapid ice volume reduction.To further investigate the periodicities and driving mechanisms of ASM changes, we applied the Ensemble Empirical Mode Decomposition (EEMD) method to analyze the stalagmite δ18O. The results indicate that on centennial scales, cycles of 94 years and 197 years respectively accounted for 37.386% and 30.325% of the variance, corresponding to the solar Gleissberg cycle and the Suess/de Vries cycle, indicating that solar activity was the primary driving mechanisms for centennial-scale ASM variability during the early Holocene. Solar activity can influence ASM intensity directly by altering the land-sea thermal contrast, or indirectly through ocean-atmosphere coupling processes. On multidecadal scale, the 73-years cycle is consistent with the 60~90 years cycle of the Atlantic Multidecadal Oscillation (AMO), suggesting that AMO changes may significantly influence the ASM by modulating atmospheric circulation patterns.