The tropical Andes of southern Peru and northern Bolivia have several major mountain summits suitable for ice core paleoclimatic investigations. However, incomplete understanding of the controls on the isotopic (δD, δ18O) composition of precipitation and a paucity of field observations in this region continue to limit ice-core-based paleoclimate reconstructions. This study examines four years of daily observations of δD and δ18O in precipitation from a citizen scientist network on the northeastern margin of the Altiplano, to identify controls on the subseasonal spatiotemporal variability in δ18O during the wet season (November-April). These data provide new insights into modern δ18O variability at high spatial and temporal scales. We identify a regionally coherent subseasonal signal in precipitation δ18O featuring alternating periods of high and low δ18O of 9-27-day duration. This signal reflects variability in precipitation delivery driven by synoptic conditions and closely relates to variations in the strength of the South American low-level jet and moisture availability over the study area. The annual layer of snowpack on the Quelccaya Ice Cap observed in the subsequent dry season retains this subseasonal signal, allowing the development of a snow-pit age model based on precipitation δ18O measurements, and demonstrating how synoptic variability is transmitted from the atmosphere to mountaintop snowpacks along the Altiplano's eastern margin. This result improves our understanding of the hydrometeorological processes governing δ18O and δD in tropical Andean precipitation and has implications for improving paleoclimate reconstructions from tropical Andean ice cores and other paleoclimate records.
Bibliographical noteFunding Information:
Acknowledgments. We thank our citizen scientist observers in Peru and Bolivia; all participants in field-work and snow pit efforts 2009–17; and university partners at UNSAAC-Cusco and UMSA-La Paz. In particular, we thank Courtney Cooper, Jason Endries, Eric Burton, Evan Montpellier, Adrián Ccahuana, Nilton Montoya, Sandro Arias, Ronald Winkelmann, Marcelo Peñaloza, and Laura Ticona for their contributions. We thank the University of Arkansas Stable Isotope Lab for analyzing samples. Finally, we thank Françoise Vimeux and two anonymous reviewers for their valuable and constructive feedback. This work is funded by U.S. National Science Foundation Grants AGS 1566450 and AGS1347179.
© 2019 American Meteorological Society.
- Automatic weather stations
- Isotopic analysis
- South America