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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 (δ18O, δ13C, 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 δ18O monsoon records. Interestingly, however, our δ13C 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 δ18O. Moreover, the δ13C 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 δ18O. Our interpretations suggest that drier conditions brought on by the 8.2 ka event in MSEA were felt beyond the temporal boundaries defined by δ18O‐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. Plain Language Summary: The most significant global climate event in the last ∼11,000 years occurred ∼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 ∼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. Key Points: 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 δ18OPrevious monsoon records of the event lack the resolution and/or multiproxy dimensions needed to reconstruct local hydrologic changes [ABSTRACT FROM AUTHOR]

Reconstructing hydroclimate over the Common Era is essential for understanding the dominant mechanisms of precipitation change and improving climate model projections, which currently suggest Northeast Mexico will become drier in the future. Tree‐ring reconstructions have suggested regional rainfall is primarily controlled by Pacific sea‐surface temperatures (SSTs). However, tree ring records tend to reflect winter‐spring rainfall, and thus may not accurately record total annual precipitation. Using the first multiproxy speleothem record spanning the last millennium, combined with results from an atmospheric general circulation model, we demonstrate mean annual rainfall in Northeast Mexico is highly sensitive to Atlantic SST variability. Our findings suggest future precipitation in Northeast Mexico is more dependent upon the warming of Tropical Atlantic SSTs relative to the Tropical Pacific. Plain Language Summary: We use geochemical markers of past rainfall in a rock from a cave (speleothem) to show that warming in Atlantic sea‐surface temperatures (SSTs) increases the amount of precipitation in Northeast Mexico. These finding are surprising, since previous rainfall reconstructions using tree rings have suggested a warmer Atlantic decreases precipitation in the region. We used a climate model to show that warming in the Atlantic increases precipitation during the summer but decreases precipitation during the winter. Although winter precipitation only accounts for 8% of annual rainfall in this region, tree rings are more reflective of the winter precipitation response. This is the first speleothem record from NE Mexico over this time‐period and suggests that projections of future rainfall should emphasize relative changes in Atlantic SST variability because it has a major impact on annual precipitation. Key Points: We present the first speleothem record spanning the last millennium from NE Mexico using multiple geochemical proxiesIn contrast to tree ring reconstructions, we suggest regional precipitation is primarily controlled by Atlantic sea‐surface temperatures (SSTs)We utilize results from a forced‐SST climate model to further support our interpretation [ABSTRACT FROM AUTHOR]

Chinese speleothem oxygen isotope (δ18O) variations have been widely interpreted as recording the evolution of the Asian Monsoon. However, calibration of δ18O to monsoon intensity has not yet been carried out in a quantitative way. To understand the climatic significance of δ18O, we measured monthly precipitation δ18O data at Heshang Cave, China, where speleothem δ18O records were previously obtained. We examined the influence of local climate and large‐scale atmospheric circulation on the δ18O by correlating to local meteorological data and various monsoon indices. We find neither a significant amount effect nor temperature effect, and therefore suggest that local climate is not the primary driver of δ18O variability. On seasonal timescales, monthly δ18O is significantly correlated to all monsoon indices, especially the Indian Monsoon (IM) and Western North Pacific Monsoon (WNPM) indices, proving δ18O responds dominantly to the tropical monsoon circulation. On interannual timescales, there are significant negative correlations between annual δ18O and the WNPM and IM monsoon indices defined by zonal winds, reflecting the impact of the El Niño‐Southern Oscillation on δ18O. Similar correlations between δ18O and precipitation amount in these monsoon regions lend further support to this finding. As the driving force of seasonal and interannual monsoon changes can be compared to variations on orbital and suborbital scales, respectively, we argue that speleothem δ18O in southern China is influenced by both external forcing and internal variability. Solar radiation plays an indispensable role on the orbital and seasonal scale δ18O variations, whereas ocean–atmosphere interactions are dominant on suborbital timescales. Key Points: Local climate conditions are not the main factor determining the precipitation oxygen isotopes in east ChinaEast Asian precipitation δ18O reflects tropical monsoons on seasonal timescales and links to air–sea interactions on interannual timescalesSolar insolation dominates speleothem δ18O on orbital timescales, and internal variability influences speleothem δ18O on suborbital timescales [ABSTRACT FROM AUTHOR]