Strong coupling of centennial-scale changes of Asian monsoon and soil processes derived from stalagmite δ¹⁸O and δ¹³C records, southern China

The paleoclimate application of speleothem δ¹³C is influenced by site-specific processes. Here we present four stalagmite δ¹³C records from two caves in southern China, covering early and late Marine Isotope Stage (MIS) 3 and the Holocene, to investigate the spatio-temporal pattern of calcite δ¹³C changes and the relationship with Asian monsoon (AM) variability. In each growth period, precessional- to millennial-scale changes are clear in the δ¹⁸O record. In contrast, millennial variability is absent in the δ¹³C record, which characterizes persistent centennial oscillations. However, centennial-scale δ¹⁸O variations agree well with those of δ¹³C, with a larger amplitude in δ¹³C changes (about twice that of δ¹⁸O). This suggests that soil humidity balance associated with regional hydrological circulations is important for these centennial δ¹³C changes, although evaporation-related kinetic fractionation can induce concurrent enrichments in δ¹⁸O and δ¹³C. In frequency, the detrended δ¹⁸O and δ¹³C records are coupled at a periodicity of about 300 yr during the last glacial period and 150 yr during the Holocene. Those centennial-scale δ¹³C variations are generally consistent with Greenland temperature variability, indicating a climate response over broad regions. Thus, strong co-variation of δ¹⁸O and δ¹³C records should have a climatic origin, even if it is amplified by kinetic effects.