Holocene climate optimum moisture variability in the monsoon marginal zone of northern China revealed by multi-proxy stalagmite records

Reconciling the diverse climate responses of various geological archives poses a challenge for a comprehensive understanding of the Holocene climate change in East Asia. Here, we present multi-proxy records of two precisely dated stalagmites from the northeastern Chinese Loess Plateau. A comparative analysis reveals that the main depositional period (∼9.6–5.9 ka BP) of one stalagmite directly corresponds to the Holocene Climate Optimum (HCO) in northern China. The stalagmite δ¹⁸O exhibits a quasi-500-year cyclicity throughout the HCO, which aligns with other records from the North Atlantic, East Asia, and Mediterranean during the cycle from ∼8.3 to 7.8 ka BP, likely reflecting the 8.2 ka event's imprint. Meanwhile, divergent phase relationships occurred during other intervals, indicating regionally distinct responses to solar-driven coupled ocean-atmosphere oscillations. Furthermore, multiple hydroclimate proxies and the stalagmite growth rate from the same stalagmite reveal a shift in the precipitation regimes, manifested as the rainy season extending from summer to autumn after ∼7.8 ka BP. Changes in the position and intensity of the subtropical westerly jet may drive this shift.