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

Abstract

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.