Laminae records of stalagmites from Tiankeng Cave in Southern China during the last 50 years and their implications for climate and environment

In the context of global warming, decadal variability of the East Asian summer monsoon(EASM)and its regional hydroclimatic responses have become a key issue in climate research. Because instrumental records are inherently limited, high-resolution natural proxy data provide an important complement to such studies. Owing to their precise chronology, continuous deposition, and high sensitivity to environmental change, stalagmites are important natural archives for reconstructing modern and recent EASM climate variability. Using 230Th and 210 Pb dating combined with annual lamina counting, this study establishes an annually resolved layer-thickness chronology for stalagmite TK22-1 collected from Tiankeng Cave (28° 19′ 28″~29° 24′ 18″ N, 108° 18′ 25″~109°19′ 02″ E) in Youyang, Chongqing, covering the period 1963~2016. Multi-proxy analyses—including lamina thickness, grayscale values, δ18O, δ13C, and trace-element ratios (Mg/Ca, Sr/Ca, Ba/Ca)—reveal that the stalagmite exhibits relatively stable growth rates, and that lamina thickness is highly sensitive to variations in regional mean annual temperature and relative humidity, thereby reliably recording local climatic and environmental changes. The temporal trends of lamina thickness show strong coherence with δ18O and δ13C values, indicating coupled changes in local temperature, number of rainy days, humidity, and soil-percolation water system processes. Comparison with meteorological observations from Youyang demonstrates that lamina thickness responds directly to regional hydrothermal conditions, with thicker layers forming during humid intervals and markedly thinner layers during dry periods. Integrating the δ18O record, lamina-thickness series, and PC1 of stalagmite TK22-1, we identify a weakened East Asian summer monsoon (EASM) event during the 1980s~1990s and an enhanced EASM phase after 2010. Furthermore, the results suggest that decadal variability of the Atlantic Meridional Overturning Circulation (AMOC) constitutes a major external forcing of EASM intensity and regional hydroclimate changes: a pronounced AMOC strengthening around 2010 aligns closely with the moisture transition recorded in the stalagmite. The Pacific Decadal Oscillation (PDO) and the El Niño -Southern Oscillation (ENSO) also exert additional modulating effects. Using high-resolution multi-proxy stalagmite records from the karst region of southeastern Chongqing, this study elucidates the climatic controls on stalagmite lamina thickness during the modern and recent periods. The results provide new high-resolution proxy evidence for understanding EASM variability in the context of global air-sea interactions, and offer an important scientific basis for reconstructing modern and recent monsoon-related climatic and environmental changes in the karst region of Southern China.