Semiquantitative Estimates of Rainfall Variability During the 8.2 kyr Event in California Using Speleothem Calcium Isotope Ratios

Cameron B. de Wet, Andrea M. Erhardt, Warren D. Sharp, Naomi E. Marks, Harold J. Bradbury, Alexandra V. Turchyn, Yiruo Xu, Jessica L. Oster

Research output: Contribution to journalLetterpeer-review

11 Scopus citations


A multiproxy record from a fast-growing stalagmite reveals variable hydroclimate on the California coast across the 8.2 kyr event and a precursor event likely caused by initial drainage of proglacial Lake Agassiz. Using speleothem δ44Ca, we develop the first semiquantitative estimates of paleorainfall variability for California through calibration with measurements of the modern climate and cave environment. We find that the magnitude of rainfall variability during the 8.2 kyr event approached the multiyear 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 multidecadal variability comparable in magnitude to the precursor event during the record. Our work suggests that speleothem calcium isotope ratios are a powerful semiquantitative means to reconstruct paleorainfall, although numerous factors must be assessed in each cave system before applying this approach.

Original languageEnglish
Article numbere2020GL089154
JournalGeophysical Research Letters
Issue number3
StatePublished - Feb 16 2021

Bibliographical note

Funding Information:
Funding was provided by the National Science Foundation (AGS‐1554998) and the National Geographic Society (NGS‐39815) (to Jessica L. Oster) and the Karst Waters Institute and the Geological Society of America (to Cameron B. de Wet). Calcium isotope analyses were supported through ERC StG 307582 CARBONSINK (to Alexandra V. Turchyn) and NERC NE/R013519/1 (to Harold J. Bradbury). We thank Mike Davies and Bruce Rogers of the Western Cave Conservancy for guidance in the field and the editor, Stacy Carolin, and two other anonymous reviewers for constructive feedback. Data are with the NOAA National Centers for Environmental Information Paleoclimatology Data repository ( ). This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE‐AC52‐07NA27344. LLNL‐JRNL‐807062.

Publisher Copyright:
© 2020. American Geophysical Union. All Rights Reserved.


  • calcium isotopes
  • climate whiplash
  • speleothem
  • strontium isotopes

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences (all)


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