High-Resolution, Multiproxy Speleothem Record of the 8.2 ka Event From Mainland Southeast Asia

The 8.2 ka event is the most significant global climate anomaly of the Holocene epoch, but a lack of records from Mainland Southeast Asia (MSEA) currently limits our understanding of the spatial and temporal extent of the climate response. A newly developed speleothem record from Tham Doun Mai Cave, Northern Laos provides the first high-resolution record of this event in MSEA. Our multiproxy record (delta 18O, delta 13C, Mg/Ca, Sr/Ca, and petrographic data), anchored in time by 9 U-Th ages, reveals a significant reduction in local rainfall amount and weakening of the monsoon at the event onset at similar to 8.29 +/- 0.03 ka BP. This response lasts for a minimum of similar to 170 years, similar to event length estimates from other speleothem delta 18O monsoon records. Interestingly, however, our delta 13C and Mg/Ca data, proxies for local hydrology, show that abrupt changes to local rainfall amounts began decades earlier (similar to 70 years) than registered in the delta 18O. Moreover, the delta 13C and Mg/Ca also show that reductions in rainfall continued for at least similar to 200 years longer than the weakening of the monsoon inferred from the delta 18O. Our interpretations suggest that drier conditions brought on by the 8.2 ka event in MSEA were felt beyond the temporal boundaries defined by delta 18O-inferred monsoon intensity, and an initial wet period (or precursor event) may have preceded the local drying. Most existing Asian Monsoon proxy records of the 8.2 ka event may lack the resolution and/or multiproxy information necessary to establish local and regional hydrological sensitivity to abrupt climate change. The most significant global climate event in the last similar to 11,000 years occurred similar to 8,200 years ago (the "8.2 ka event"). Many globally distributed records of past climate (paleoclimate) document significant changes during the event, but there are few from Mainland Southeast Asia available to reconstruct the climate impacts in this region. We present a new speleothem (cave sample) record from Tham Doun Mai Cave, Northern Laos that uses multiple geochemical and physical signals (proxies) to document local and regional climate effects of the 8.2 ka event at a high resolution. Using oxygen isotopes, we find that the 8.2 ka event weakened regional monsoon intensity for at least similar to 170 years, which resembles findings from other studies. However, other proxies suggest local rainfall changed abruptly decades before the signal of monsoon weakening. Additionally, local drying may have lasted much longer than current estimates of 8.2 ka event responses. Most proxy records of the 8.2 ka event in monsoon regions lack similar multiproxy information and/or do not have high enough resolution to fully capture the climatic response. Additional records like ours from monsoon regions may assist in establishing how sensitive local and regional rainfall is to abrupt climate change. High-resolution speleothem record of the 8.2 ka event in northern Laos shows weakened monsoon intensity and reduced local rainfall amountsMultiproxy data suggest the disruption to local rainfall amounts started decades before the weakened monsoon intensity inferred from delta 18OPrevious monsoon records of the event lack the resolution and/or multiproxy dimensions needed to reconstruct local hydrologic changes