Asynchronous Holocene Optimum in East Asia monsoon region recorded by stalagmites and its underlying climate dynamics

• Main Authors: Liang, Mingqiang, Yin, Qiuzhen, Li Hong-Chun, Sun Yong, Peter Hopcroft, Li Ting-Yong, Wu, Zhipeng, XXI Congress of the International Union for Quaternary Research (INQUA) 2023
• Other Authors: UCL - SST/ELI/ELIC - Earth & Climate
• Format: Conference Object
• Language: English
• Published: 2023
• Subjects: Holocene Optimum; East Asia monsoon; speleothem; Ice Sheet
• Online Access: http://hdl.handle.net/2078.1/281835

Reconstructions of Holocene Optimum (HO) in East Asian summer monsoon (EASM) regime from speleothem versus other proxy records have yielded divergent phase relationships with the EASM and local precipitation. This apparent discrepancy has been partly attributed to the uncertainties in the climatic representation of Chinese speleothem oxygen isotope (δ18O) records. Here we conducted a data-model comparison along with a water moisture budget analysis to assess the role of thermodynamic and dynamic components in controlling mid-summer and spring rainfall during early and mid-Holocene, and to compare with the precipitation changes referred by the stalagmite δ18O records. Our results show that 1) a marked southward shift of the HO period from 10000~6500 yr BP in North China (NC) to 9000~5500 yr BP in Yangtze river valley (YRV). During the Holocene, the variation of the summer total precipitation is dominated by precession in NC, ice sheet in YRV. 2) An incoherent orbital-scale speleothem δ18O variability in EASM regime indicate that speleothem δ18O is largely controlled by the large-scale circulation and concomitant latitude shifts of monsoon rain belt.3) The intensified hydroclimate in YRV in mid-Holocene was contributed to excessive rainfall in summer, especially for increasing the convection/total precipitation ratio, which leads to the lightest speleothem δ18O during the mid-Holocene. The excessive rainfall in summer mainly from the enhancement of convective activities that is caused by the southward shift of monsoon rain belt.