Different Precipitation Spatial Patterns during the 2.8 ka BP event between Southwest China and Central China：Link to Asian Monsoon and Westerly

The increasing frequency of droughts and floods caused by the spatial variability of precipitation in East China has affected hundreds of millions of human beings. Meteorological observations indicate that both Asian summer monsoon (ASM) and westerly contribute significantly to the spatial pattern of precipitation in East China, but whether it is the same in pre-industrial period remains unclear. The 2.8 ka BP climate event, occurred in the late Holocene with a lower atmospheric CO2 concentration and a pronounced variability of ASM and westerly, provides an ideal target to investigate the precipitation variability and its mechanisms in East China. In this study, we reconstructed an annual stalagmite oxygen isotope (δ18O) record from 2950 to 2430 a BP based on an annually laminated stalagmite (HS4) from Heshang Cave, Qingjiang valley, Central China. Then the reconstructed record was compared with another annual-resolved stalagmite (QX1) δ18O record from Southwest China to explore the rainfall spatial variations and its potential driving mechanisms between the two regions during the 2.8 ka BP event, and its consistency with modern climate has been discussed. It was observed that the precipitation spatial patterns between Southwest China and Central China were the same before and after the 2.8 ka BP event, while an anti-phase pattern emerged during the event, which is in agreement with modern precipitation spatial pattern, suggesting that the rainfall spatial variability between Southwest China and Central China during the 2.8 ka BP event is probably triggered by the westerly-monsoon interactions and with less connection with atmospheric CO2.