Stable isotopes in global precipitation: A unified interpretation based on atmospheric moisture residence time

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Abstract

[1] We present a new approach based on atmospheric moisture residence time (RT) to interpret precipitation stable isotope ratio variations in all climate regimes, including tropical and polar, on monthly or inter-annual time scales.δ18O and ln RT are positively correlated and a single regression line describes variations in δ18O and RT anomalies, overcoming limitations of existing Rayleigh distillation-based approaches for tracing moisture dynamics and precipitation processes. We use this approach to characterize changes in tropical precipitation during El Nino events and suggest that increased precipitation in a warmer climate may occur with higherδ18O values, contrary to assumptions made in interpreting proxy climate records in speleothems and other archives. Our results will allow the use of isotopes to monitor climate change impacts on the character and intensity of precipitation and to improve the performance of climate models by providing a direct means to calibrate model results.

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