EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Pacific Walker circulation variability during the last millennium reconstructed from a network of water isotope proxy records

Georgina Falster1, Bronwen Konecky1, Sloan Coats2, Samantha Stevenson3, and Midhun Madhavan3,4
Georgina Falster et al.
  • 1Washington University in St. Louis, Earth and Planetary Sciences, St. Louis, United States of America (
  • 2University of Hawaii at Manoa, Department of Earth Sciences, Honolulu, United States of America
  • 3University of California Santa Barbara, Bren School of Environmental Science & Management, Santa Barbara, United States of America
  • 4The University of Michigan, Department of Earth and Environmental Sciences, Ann Arbor, United States of America

Changes in the strength of the Pacific Walker circulation (PWC) can have a significant impact on global mean surface temperatures, as well as regional temperature, precipitation, and extreme weather events far beyond the tropical Pacific. Understanding PWC variability is therefore important for constraining future climate. But observational records of the PWC are short, and single-site proxy records for changes in the strength of the PWC during the last millennium offer contrasting interpretations. This leaves a critical gap in our understanding of PWC variability on the decadal to centennial timescales relevant to future climate change.

Falster et al. (in prep.) demonstrated that the PWC is strongly imprinted in modern global precipitation δ18O (δ18OP). This relationship arises via multiple complementary mechanisms, including but not limited to ENSO dynamics. We exploit this relationship to reconstruct changes in the strength of the PWC over the past millennium, using six different statistical and machine learning reconstruction methods in conjunction with a globally-distributed network of palaeo-δ18OP records (Konecky et al. 2020). Although δ18OP from a relatively small number of locations explains a large proportion of PWC variance in the calibration interval, we use a larger network of sites because larger networks are less susceptible to non-stationary teleconnections or non-signal biases than individual sites or smaller networks. 

Preliminary results indicate that reconstructed PWC variability is coherent across methods, particularly for the past 400 years. Our reconstructions are also robust to both the calibration window used, and the particular palaeo-δ18OP records included in the reconstruction. This provides confidence that our network comprises sufficient proxy timeseries i.e. that we successfully extracted the common underlying climate signal (the PWC) from site-specific information inherent in individual palaeo-δ18OP records. Thus, we are confident that our reconstruction of changes in the strength of the PWC through the last millennium is robust, and it will therefore help to constrain the PWC’s long-term internal variability and sensitivity to external forcing.


Falster, G. M., B. Konecky, M. Madhavan, S. Coats, S. Stevenson. 2021. “Imprint of the Pacific Walker circulation in global precipitation δ18O”. In preparation for Journal of Climate

Konecky, B. L., N. P. McKay, O. V. Churakova (Sidorova), L. Comas-Bru, E. P. Dassié, K. L. DeLong, G. M. Falster, et al. 2020. “The Iso2k Database: A Global Compilation of Paleo-δ18O and δ2H Records to Aid Understanding of Common Era Climate.” ESSD.

How to cite: Falster, G., Konecky, B., Coats, S., Stevenson, S., and Madhavan, M.: Pacific Walker circulation variability during the last millennium reconstructed from a network of water isotope proxy records, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3748,, 2021.


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