NOAA/WDS Paleoclimatology - White Moon Cave, California 8.2ka Calcium and Strontium Isotope Data

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 d44Ca, 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.