High‐Resolution, Multiproxy Speleothem Record of the 8.2 ka Event From Mainland Southeast Asia
Christopher T. Wood, Kathleen R. Johnson, Lindsey. E. Lewis, Kevin T. Wright, Jessica K. Wang, Andrea Borsato, Michael L. Griffiths, Andrew J. Mason, Gideon M. Henderson, Jacob Setera, Silvia Frisia, Sengphone Keophanhya, Joyce C. White
Abstract
Abstract 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 (δ 18 O, δ 13 C, 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 ∼8.29 ± 0.03 ka BP. This response lasts for a minimum of ∼170 years, similar to event length estimates from other speleothem δ 18 O monsoon records. Interestingly, however, our δ 13 C and Mg/Ca data, proxies for local hydrology, show that abrupt changes to local rainfall amounts began decades earlier (∼70 years) than registered in the δ 18 O. Moreover, the δ 13 C and Mg/Ca also show that reductions in rainfall continued for at least ∼200 years longer than the weakening of the monsoon inferred from the δ 18 O. Our interpretations suggest that drier conditions brought on by the 8.2 ka event in MSEA were felt beyond the temporal boundaries defined by δ 18 O‐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.