Remote vs. local control on the Preboreal Asian hydroclimate and soil processes recorded by an annually-laminated stalagmite from Daoguan Cave, southern China

Stable isotopic measurements on the upper 168 cm of stalagmite DG24 from southern China, which is annually-laminated above 74.8 cm (∼11.8 ka), reconstruct a history of detailed Asian summer monsoon (ASM) variability and soil processes between 14.8 and 10.3 ka. The climate sequence of Bølling-Younger Dryas (YD)-Preboreal events is evident in δ¹⁸O record. In the Preboreal, four-year-resolution and annually-counted δ¹⁸O record reveals that the ASM strengthening can be divided into three phases, with a prominent and persistent rise initiated at about 11.2 ± 0.3 ka, likely in response to interactions between ocean, atmosphere, and ice sheets. In contrast, the long-term δ¹⁸O depletion is absent in the δ¹³C and annual layer records, which characterize persistent centennial oscillations and likely represent relative humidity of the soil. At multi-decadal scale, prominent ASM failures are generally consistent with periods of δ¹³C enrichment and decreased layer thickness. When compared with solar proxies, centennial-scale δ¹³C changes match well with solar activity regardless of the observed disparity between ASM and solar records, and common cycles of 130 and 300 years are identified in both the atmospheric Δ¹⁴C and speleothem δ¹³C records. This implicates that during the Preboreal local soil humidity budget and CO₂ production, indicated by the δ¹³C and annual layer records, is more sensitive to changes in solar output than the regional hydroclimate variability recorded by the δ¹⁸O signal.