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Large isotope signals in tropical precipitation require large-scale changes in rainout
  • +4
  • Tyler Kukla,
  • N Siler,
  • R P Fiorella,
  • M M Laguë,
  • C Hvam,
  • J K C Rugenstein,
  • A L S Swann
Tyler Kukla

Corresponding Author:[email protected]

Author Profile
N Siler
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University
R P Fiorella
Earth and Environmental Sciences Division, Los Alamos National Laboratory, New Mexico Consortium
M M Laguë
Department of Atmospheric Sciences, University of Utah, Department of Geography, University of British Columbia
C Hvam
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University
J K C Rugenstein
Department of Geosciences, Colorado State University
A L S Swann
Department of Atmospheric Sciences, University of Washington, Department of Biology, University of Washington

Abstract

In the tropics, oxygen isotope signals of past climate change range from less than 1‰ to upwards of 7‰ or more. Regardless of the amplitude, these signals are often interpreted to reflect changes in local rainout. However, stable isotopes in precipitation can carry information about rainout across thousands of kilometers, making it hard to parse the local and non-local effects. Here, we present a framework that links the amplitude of tropical isotope signals to spatial patterns of climate change that cause them. Using three models of varying complexity, we show that the largest signals require coherent hydrologic change across ~1,000 to 8,000 kilometers. This pattern can be explained by the balance of vapor being rained out versus replenished as it moves over space. Within ~1,000 kilometers, upwind changes in rainout are too localized for a large isotope shift to emerge. Beyond ~8,000 kilometers, the rainout signal is overwhelmed by more locally-sourced vapor. We find that rainout in this ~1,000-8,000 km upwind window causes the largest isotope shifts in tropical paleoclimate, even when the isotope composition is strongly correlated with local precipitation amount. Our results indicate that large amplitude isotope signals are reliable tracers of large scale hydrologic change, and their link to local precipitation amount is tenuous. 
07 May 2024Submitted to ESS Open Archive
10 May 2024Published in ESS Open Archive