[U-05] Advanced understanding of Quaternary and Anthropocene hydroclimate changes in East Asia

[U05-02] Moisture transport pathway effect evidenced by triple oxygen isotopes in central Myanmar speleothems

★Invited Papers

*Xianfeng Wang^1,2, Meilun Zhang¹, Shufang Yuan², Lijuan Sha³ (1.Asian School of the Environment, Nanyang Technological University, Singapore, 2.Earth Observatory of Singapore, Nanyang Technological University, Singapore, 3.Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an, China)

Keywords:moisture transport pathway, triple oxygen isotopes, speleothems, Asian monsoon

The interpretation of the iconic Chinese speleothem d¹⁸O records remains debated, in part because the records contain muted glacial-interglacial variability, distinctly different from the majority of other proxy records from the Asian monsoon region. Here, we extended a speleothem record from central Myanmar, now covering a large portion of the past 40,000 years. When comparing with other cave records from locations along the trajectory of the Indian summer monsoon, our record from central Myanmar confirms our previous observations, that is, a larger d¹⁸O gradient along the moisture trajectory during the glacial time relative to today. We also performed triple oxygen isotope (¹⁶O-¹⁷O-¹⁸O) analysis on the speleothems. We found that ¹⁷O-excess of monsoon precipitation during the last glacial maximum (LGM) is ~26 ± 2 per meg, substantially higher than the value of ~15 ± 5 per meg in modern times. The decrease of 10 per meg in ¹⁷O-excess from the LGM to Holocene probably indicates an increase in relative humidity (RH) of monsoon moisture. Thus, during the glacial time, there existed a significant drop in RH, corresponding to a stronger continental re-evaporation and possibly suppressed plant transpiration. Both our speleothem d¹⁸O and ¹⁷O-excess results therefore support our hypothesised mechanism of the moisture transport pathway effect in addressing the d¹⁸O variability in Chinese speleothem records.