Stalagmite records of spatiotemporal hydroclimatic variations in monsoonal China during 47–12 ka BP

Recent high-resolution sediment records, such as Greenland ice cores and Chinese stalagmites, have greatly enhanced our understanding of millennial-scale climate variability during Heinrich Stadials (HSs) of the Last Glacial Period, particularly highlighting the diminished intensity of the Asian Summer Monsoon (ASM). These records reveal precise temporal correlations between high-latitude climate changes and low-latitude monsoon variability, especially in the Asian monsoon region. However, the scarcity of stalagmite records from southeastern China has limited our understanding of the spatio-temporal patterns of monsoonal precipitation variability during these abrupt climate events, as most published records are concentrated in central-northern and southwestern China. In this study, we present a high-resolution hydroclimate reconstruction based on stalagmite YXG01 from Yindi Cave, Hubei Province, China, using 42 U-Th dates and 698 δ¹⁸O and δ¹³C isotope measurements, spanning the 11.92–47.47 ka BP interval. Our δ¹⁸O record shows four positive excursions, indicating significantly weakened ASM intensity during the four most recent HSs (HS1 to HS4), consistent with previous studies. During these HSs, freshwater influx into the North Atlantic weakened the Atlantic Meridional Overturning Circulation, cooled Northern Hemisphere temperatures, and reduced ASM circulation/intensity, resulting in consistent positive δ¹⁸O shifts in precipitation and stalagmites across the East Asian monsoon region. We found that the amplitude of stalagmite δ¹⁸O variations during the HSs decreases progressively from Southwest China to Southeast China, a trend that aligns with simulated changes in precipitation δ¹⁸O. The smaller amplitude of δ¹⁸O shifts in southeastern China during the HSs may be linked to increased moisture contributions from the western Pacific Ocean and enhanced local precipitation. During these HSs, anti-phased variations between YXG01 δ¹⁸O and δ¹³C, together with temperature reconstructions and model simulations, suggest favorable hydroclimatic conditions in the mid-lower reaches of the Yangtze River Valley. Increased precipitation and moderate temperature may have enhanced vegetation growth, resulting in lower speleothem δ¹³C values despite the overall weakening of ASM circulation. Our new speleothem YXG01 record reveals two important observations from Southeast China: a smaller amplitude of speleothem δ¹⁸O shifts and anti-phased δ¹⁸O and δ¹³C variations during the HSs. Further model simulations are necessary to fully explore the underlying climate dynamics driving these patterns.