A SPELEOTHEM RECORD OF LATE HOLOCENE HYDROCLIMATE VARIABILITY IN CENTRAL LAOS

Most of mainland Southeast Asia (MSEA) is dominated by the Southeast Asian monsoon system, which delivers the majority of annual rainfall during the summer monsoon season, which is closely linked to the seasonal migration of the ITCZ. While climate models project that temperatures will keep rising during the incoming years in MSEA, models disagree about the sign and spatial pattern of future rainfall change. Paleoclimate records are urgently needed from this region, to understand the factors driving forced and unforced hydroclimate variability in this sensitive region and to improve model projections. To address this, we have developed a new high-resolution speleothem stable isotope record from a ~45 cm long U-Th dated stalagmite (TNM-1) collected from Tham Ngeun Mai cave, located in Khammouane province, central Laos. The age model is constrained by 20 U-Th dates which indicate that the sample formed from ~4 kyr BP to present. Here we present a preliminary stable carbon and oxygen isotope record, that records significant decadal to centennial scale-variability in both proxies. We interpret δ18O variations as reflecting large-scale moisture/rainfall patterns and variations in monsoon intensity, whereas δ13C is primarily influenced by local water balance. We compare our record with other speleothem data from MSEA, including with a Central Vietnam stalagmite that primarily records autumn and winter monsoon intensity. The interpretation of our record is ground-truthed with 2 years of cave monitoring data from TNM, and will also be informed by preliminary 14C and trace element measurements.