Reinterpreting Precipitation Stable Water Isotope Variability in the Andean Western Cordillera Due To Sub-Seasonal Moisture Source Changes and Sub-Cloud Evaporation

Lisa R. Welp, Elizabeth J. Olson, Adriana Larrea Valdivia, Juan Reyes Larico, Efraín Palma Arhuire, Lino Morales Paredes, Jonathan T. DeGraw, Greg M. Michalski

Research output: Contribution to journalArticlepeer-review

Abstract

Precipitation in the arid Central Andean Western Cordillera is strongly sensitive to large-scale atmospheric circulation patterns which transport moisture from different source regions. As a result, the stable water isotopes of precipitation in this region have been difficult to interpret. We analyzed daily rainfall in the southern Peruvian city of Arequipa for water stable isotopes during the 2019 monsoon season to study sub-seasonal precipitation dynamics. At 2,300 masl elevation, most rain was sourced from easterly moisture transported over the Altiplano, and was isotopically enriched (δ18O = −5.2‰), likely due to sub-cloud evaporation. This was contrary to literature expectations that enriched isotopic values indicate Pacific moisture. During a 2-week period of northerly moisture transport and intense rainfall, we observed rain stable water isotopes shifted to depleted values (δ18O = −10.3‰). This study provides new context for interpreting time-varying and elevation-varying moisture source influence in the Western Cordillera.

Original languageEnglish
Article numbere2022GL099876
JournalGeophysical Research Letters
Volume49
Issue number18
DOIs
StatePublished - 28 Sep 2022

Bibliographical note

Funding Information:
The authors are grateful to local volunteers that made this project possible. The Arequipa Nexus Institute for Food, Water, Energy, and the Environment (https://www.purdue.edu/discoverypark/arequipa-nexus/) provided funding. The authors acknowledge the NOAA Air Resources Laboratory (ARL) for providing the HYSPLIT transport and dispersion model used in this publication. The authors thank H. Harshvardhan for his expert guidance on precipitation remote sensing datasets and M. Huber for discussions on ERA-5 reanalysis products. J. DeGraw was partially supported by the Discovery Park Undergraduate Research Internship Program.

Publisher Copyright:
© 2022. The Authors.

Keywords

  • Andes
  • flooding
  • hydrogen isotopes
  • moisture source
  • orographic
  • oxygen isotopes
  • precipitation
  • South American summer monsoon
  • stable isotopes
  • Western Cordillera

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