A long-term trend toward wetter conditions during MIS 2 inferred from modern-monitoring-based stalagmite multi-proxy records from Remi Cave, Central China

The ongoing debate regarding the spatial pattern of precipitation and effective moisture changes in monsoonal eastern China during the Marine Isotope Stage 2 (MIS 2) centers on the hydroclimatic evolution of the middle and lower Yangtze River Valley. Here, we present an approximately four-year (December 2020 to December 2024) systematic modern monitoring program and multi-proxy records (δ 18 O, δ 13 C, Mg/Ca, Sr/Ca, Ba/Ca) from stalagmite RM4 in Remi cave, Hunan Province, Central China, spanning ∼25.7‒14.5 kyr BP. Based on modern monitoring results and cross-validation among multi-proxy records, the δ 13 C values and Sr/Ca and Ba/Ca ratios in the stalagmite RM4 record are interpreted as qualitative indicators of an integrated effective-moisture signal, whereas variations in RM4 δ 18 O appear to be mainly associated with large-scale atmospheric circulation. During the ∼25.7–14.5 kyr BP interval, the δ 13 C, Sr/Ca, and Ba/Ca records from stalagmite RM4, complemented by various records from nearby stalagmites and peat bogs, indicate an overall long-term trend toward increased effective moisture in central China. This trend is consistent with precipitation reconstructions from northeastern China, but contrasts with contemporaneous long-term drying trends reported in northern and southern China, which may point to a quadrupole-like pattern of hydroclimatic change across monsoonal eastern China. We suggest that this marked spatial heterogeneity in hydroclimate may have been modulated by zonal sea surface temperature gradients across the tropical Pacific, which may have influenced the position and intensity of the West Pacific subtropical high and possibly triggered a cyclonic anomaly to its north through the western North Pacific anomalous anticyclone. Our results highlight the value of integrating modern cave monitoring, with multi-proxy records from various archives for understanding the controlling mechanisms of stalagmite proxy records.