Tree-ring oxygen isotope chronology of teak log coffins in northwestern Thailand and its relationship with Pacific Decadal Oscillation and El Niño-Southern Oscillation

Abstract

We developed a stable oxygen isotope chronology of tree-ring alpha cellulose (δ18OTR) from archaeological teak (Tectona grandis L.f.) samples from Mae Hong Son (MHS) province, northwestern Thailand. The samples were collected from ancient coffins belonging to the log coffin culture excavated at the Ban Rai rock shelter (BR). The chronology spans a period of 283 years in the late Holocene (AD14–296). The oxygen isotopic composition of BR δ18OTR ranged from 21.15‰ to 26.31‰. Since δ18OTR variations in Thailand teak can be used as indicators for precipitation amount during the rainy summer monsoon season, our chronology can be used as a proxy for regional late Holocene hydroclimate variability. This is confirmed by a significant positive correlation of our BR δ18OTR record with a stalagmite δ18O record from Klang cave, southern Thailand (r = 0.303, p < 0.01). In addition, a REDFIT spectral analysis revealed the existence of multidecadal (26.9-year) and interannual (5.6, 3.4 and 2.8-year) cycles, which may potentially be the fingerprints of climate forcing mechanisms impacting Thailand monsoon precipitation, such as the Pacific Decadal Oscillation (PDO) and the El Niño-Southern Oscillation (ENSO).