Hydroclimate variability of western Thailand during the last 1400 years

Abstract

<p>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 (δ<sup>18</sup>O, δ<sup>13</sup>C, 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 δ<sup>13</sup>C, trace elements and grayscale values suggest centennial-scale fluctuations driven by local hydrological process at the cave site. In contrast, variations in stalagmite δ<sup>18</sup>O 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 δ<sup>18</sup>O 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.</p>

Inter-annual and intra-annual tree-ring oxygen isotope signals in response to monsoon rainfall in northwestern Thailand

“…Thailand's instrumental climate data cover only relatively short periods since the second half of the 20th century or less, past climate information needs to be derived from natural archives, for example, speleothems (Chawchai et al, 2018(Chawchai et al, , 2020, pollen (Punwong et al, 2018), sediments (Chawchai, 2014;Chawchai et al, 2013), and tree-rings (Borgaonkar et al, 2001;Buareal et al, 2020;Buckley et al, 2007;Muangsong et al, 2019;Preechamart et al, 2018Preechamart et al, , 2022Pumijumnong et al, 1995Pumijumnong et al, , 2021b are essential to better understand the paleoenvironment and long-term climatic trends (Bender, 2013;Jackson and Hobbs, 2009). Among the natural archives, tree-rings are a precious source of climate variability because they provide precisely dated and annually resolved proxies of past climate (Cook and Kairiukstis, 1990;Foroozan et al, 2015;Fritts, 1976;Gagen et al, 2011;McCarroll and Loader, 2004;Pumijumnong et al, 2020bPumijumnong et al, , 2020cRahman et al, 2017;Speer, 2012;Upadhyay et al, 2021;Zhang, 2015).…”