Sixty-year quasi-period of the Asian monsoon around the Last Interglacial derived from an annually resolved stalagmite δ¹⁸O record

The 60-year quasi-periodic variability of the Asian monsoon in the mid-late Holocene has been found to be widespread in instrumental and various terrestrial records. However, whether this period exists in the older interglacial periods remains to be further studied. This paper is based on an 1840-mm-long stalagmite with clear annual laminae (with a growth rate of about 1 mm/yr) from Yongxing Cave, China, that allows for the reconstruction of the Asian monsoon evolution sequence during the period ~123.20–121.21 kyr BP. The stalagmite record closely tracks the 65°N solar insolation changes as a whole, indicating the dominant control of solar insolation on the Asian summer monsoon. After removing the solar insolation signal from the YX108 record, the δ¹⁸O residuals (Δδ¹⁸O) show 28 multidecadal monsoon cycles. The average amplitude of these fluctuations is larger than 0.8‰, with a duration typically ranging from 50 to 80 yr (about 64 yr on average), which is very similar to the mid-late Holocene Asian monsoon variability. Further, wavelet analysis displays a significant quasi-periodicity of 60 years throughout the studied period, providing further evidence for assessing whether the 60-year quasi-periodic variability of the Asian monsoon found in the Holocene exists in older periods. Our study thus suggests that this quasi-periodic variability not only occurred during the modern period but also existed in the Last Interglacial, and their influence may even be an intrinsic characteristic of the Asian monsoon system during glacial-interglacial cycles. We manifested that the interactions between solar activity and the Atlantic Multidecadal Oscillation may be the main reason for the 60-year quasi-period of the Asian monsoon.