Hydrogen isotope data of DN-1 core

Exploring the processes involved with hydroclimate changes during the Mystery Interval (MI) will enhance understanding of the global climate system. The associated mechanism of seasonal variations of rainfall in the East Asian Summer Monsoon (EASM) region during the MI remains poorly known. Here we show that the δ2H values of leaf wax n-alkanes (δ2Halk) in a wetland core retrieved from southern China remain relatively negative during the MI. Considering the primary synthesis time of leaf waxes in deciduous woody plants and the seasonal variations of precipitation δ2H in the EASM, we interpret the low δ2Halk as the early onset of summer rainfall during the MI. The early onset of summer rainfall was likely due to the early northeastward shifting of the Western Pacific subtropical high as the result of the low land-sea thermogradient between the Qinghai-Tibet Plateau and West Pacific Ocean during late-spring to early-summer.