Orbital- and millennial-scale hydroclimate changes in central China during the last glacial period

Spatial differences of rainfall in monsoonal China during the last glacial period remain contentious. Here, we present new ²³⁰Th-dated stalagmite records (δ¹³C and δ¹⁸O) from central China (the Yangtze River valley), spanning approximately 75–10 ka BP, to address this issue. We interpret the stalagmite δ¹³C variations primarily as indicators of regional rainfall changes, which show significantly decreased rainfall during MIS 4 and late MIS 3 to MIS 2. On the millennial timescale, the δ¹³C record indicates decreased rainfall during Heinrich (H) events and increased rainfall during Dansgaard-Oeschger interstadials. The strong correlations between our δ¹³C record and the westerly proxies suggest that the westerly jet played a crucial role in influencing rainfall patterns in monsoonal China throughout the last glacial period. We propose that rainfall changes in central China were consistent with northern China on both orbital and millennial timescales during the last glacial period. This observation contrasts with the modern rainfall differences between northern and central China. Our results imply that with a colder climate in high northern latitudes, the rain belt over monsoonal China influenced by the westerly jet shifted further south beyond the Yangtze River Valley during MIS 4, late MIS 3 to MIS 2 and H events, leading to a consistent decrease in rainfall over central and northern China. In contrast to the rainfall records, the stalagmite δ¹⁸O values were more negative during late MIS 3. The δ¹⁸O variations on the orbital timescale are likely related to the changes in the tropical ocean conditions controlled by insolation, which determines the δ¹⁸O values in evaporated moisture before its transport into the Asian continent. On the millennial timescale, our δ¹³C and δ¹⁸O records exhibit coupled variations, implying that the stalagmite δ¹⁸O variations are consistent with the rainfall changes in central and northern China.