资源环境科技发展态势分析平台

A multi‐proxy record from a fast‐growing stalagmite reveals variable hydroclimate on the California coast across the 8.2kyr event and a precursor event likely caused by initial drainage of proglacial Lake Agassiz. Using speleothem δ⁴⁴Ca, we develop the first semi‐quantitative estimates of paleo‐rainfall variability for California through calibration with measurements of the modern climate and cave environment. We find that the magnitude of rainfall variability during the 8.2kyr event approached the multi‐year variability observable in the recent past (1950–2019) and the magnitude of variability during the precursor event likely exceeded this range. Additionally, we observe other instances of multi‐decadal variability comparable in magnitude to the precursor event during the record. Our work suggests that speleothem calcium isotope ratios are a powerful semi‐quantitative means to reconstruct paleo‐rainfall, although numerous factors must be assessed in each cave system before applying this approach.