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Seasonal Variations in Triple Oxygen Isotope Ratios of Precipitation in the Western and Central United States
Citation:
Aron, P., S. Li, J. Renee Brooks, J. Welker, AND N. Levin. Seasonal Variations in Triple Oxygen Isotope Ratios of Precipitation in the Western and Central United States. Paleoceanography and Paleoclimatology. John Wiley & Sons, Inc., Hoboken, NJ, 38(4):e2022PA004458, (2023). https://doi.org/10.1029/2022PA004458
Impact/Purpose:
Tracers that help us understand atmospheric interactions within the hydrologic cycle and how they might impact atmospheric pollutant dynamics are rare. Triple oxygen isotope ratios (?'17O) are one such possible tracer, but their use has been hampered by the difficult of the measurement. Recent technological advancements have made ?'17O measurements more abundant, but we lack understanding of continental-scale precipitation ?'17O variability. In this manuscript, we use a unique dataset to explore sources of variation. We found a distinct seasonal signal providing a new framework from which to interpret triple oxygen isotope data in modern systems.
Description:
Triple oxygen isotope ratios (?'17O) offer new opportunities to improve reconstructions of past climate conditions by quantifying evaporation, paleohumidity, and diagenesis in geologic archives. However, the utility of ?'17O in paleoclimate applications is hampered by a limited understanding of continental-scale precipitation ?'17O variability. To explore the range and controls of precipitation ?'17O on a continental scale, we present d18O, d-excess, and ?'17O data from a network of 26 precipitation sites in the western and central United States and three streams from the Willamette River Basin in western Oregon. We find that ?'17O tracks evaporation but is insensitive to many controls that govern variation in d18O, including Rayleigh distillation, elevation, latitude, longitude, and local precipitation amount. The dominant ?'17O variability is a seasonal pattern with higher amount-weighted average precipitation ?'17O values in the winter (40 ± 15 per meg (± standard deviation)) than in the summer (18 ± 18 per meg). This seasonal pattern, which is absent in d-excess and opposite in sign from d18O, appears in other datasets globally and likely relates to a combination of subcloud evaporation, atmospheric mixing, moisture recycling, sublimation, and/or relative humidity. These seasonal ?'17O averages differ from the mean ?'17O value (33 per meg) that is often used to represent ?'17O values for unevaporated meteoric waters. Therefore, our findings provide a new framework from which to interpret triple oxygen isotope data in modern systems and apply ?'17O data to paleoclimate questions.
URLs/Downloads:
DOI: Seasonal Variations in Triple Oxygen Isotope Ratios of Precipitation in the Western and Central United States