Speleothem records in southeastern China provide key evidence for past environmental changes. However, the climatic interpretation of these proxies has remained a great controversy. Earlier work interprets the cave δ18O signal associated with regional rainfall of the East Asia Summer Monsoon (EASM) or monsoon rainfall upstream of China. Recent isotope modeling supports the latter but show little correspondence between the precipitation δ18O and rainfall in China. Here, we examine the evolution of the climate and precipitation δ18O for the last 21,000 years in models and observations. Recognizing the regional difference of the EASM rainfall, we propose an interpretation of the Chinese δ18O record that reconciles its representativeness of EASM and its driving mechanism of upstream depletion. The δ18O records do represent the intensity of the EASM system. The monsoon intensity is best characterized by enhanced southerly monsoon winds, which correlate strongly with negative δ18O over China and enhanced monsoon rainfall in northern China, as well as the continental scale Asian monsoon rainfall response in the upstream regions.
Bibliographical noteFunding Information:
The authors would like to thank the helpful discussions with Drs. D. Battisti, Ming Tan, Shaowu Wang and Zhishen An. This research is funded by NSFC41130105 , CAS/SAFEA International Project (KZZD-EW-TZ-08) , NSFC41230524 , NSFC40921120406 and US NSF and DOE . The computation is carried out at Oak Ridge National Lab and the NCAR supercomputing facility. This paper is CCR contribution 1162.
- Climate modeling
- East Asia summer monsoon
- Isotope modeling
- Oxygen isotope