Hydroclimate variability of western Thailand during the last 1400 years

Mainland Southeast Asia is located on the route of moisture transport of the Indian summer monsoon where hydroclimate records from speleothems have rarely been investigated. Here we present a new multi-proxy data set (δ¹⁸O, δ¹³C, trace elements and grayscale values) of stalagmite KPC1 from Khao Prae cave in western Thailand spanning from approximately 500 CE to 1900 CE. Our multi-proxy data reveal high variability between wet and dry periods during 500-850 CE and 1150-1350 CE, a stable condition between 850-1150 CE, and an overall trend towards dry conditions since 1350 CE. The δ¹³C, trace elements and grayscale values suggest centennial-scale fluctuations driven by local hydrological process at the cave site. In contrast, variations in stalagmite δ¹⁸O reflect integrated changes in rainfall amount from the Indian summer monsoon, supported by two-year monitoring rainfall data. In comparison with other Asian Monsoon records for the last millennia, the KPC1 record shows similarity with speleothem δ¹⁸O records from India, as well as lakes and tree-ring data from mainland Southeast Asia but diverges from records from equatorial regions and the western Pacific. We conclude that hydroclimate variability in the western side of Mainland Southeast Asia is mainly driven by changes in moisture transport from the Indian summer monsoon and modulated by expansion and contraction of the Intertropical convergent zone (ITCZ). However, Pacific Walker circulation (PWC) may have been the overriding control on precipitation on the eastern sides of Mainland Southeast Asia located closely to the western Pacific.