Indo-Pacific Warm Pool convection and ENSO since 1867 derived from Cambodian pine tree cellulose oxygen isotopes

Zhu, Mengfan; Stott, Lowell; Buckley, Brendan M.; Yoshimura, Kei; Ka, Roy

The Indo-Pacific Warm Pool (IPWP) is a major source of heat and moisture to the atmosphere and thus strongly influences the global climate. In this study, we investigate how moisture fluxes from the IPWP influence the stable isotope signature of precipitation over Southeast Asia by analyzing the oxygen isotopic composition (δ^18O) of tree cellulose from southern Cambodia. The cellulose δ^18O record, spanning AD 1867-2006, documents a regular seasonal cycle with an average amplitude of ~4‰ that is primarily controlled by seasonal differences in the isotopic composition of precipitation. Using the outputs from an isotope-enabled atmospheric model, we illustrate how the δ^18O of precipitation at our site is predominantly controlled by the amount of rainout that occurs over the moisture source region, the IPWP. This is verified by strong correlations of our cellulose δ^18O record with instrumental measurements of precipitation and outgoing longwave radiation over the IPWP, suggesting that the cellulose δ^18O could be used to reconstruct the convection intensity over the IPWP. Spectral analysis of the cellulose δ^18O reveals significant peaks at 2-7 years corresponding to ENSO frequencies. The variability of the cellulose δ^18O record on the ENSO band exhibits characteristics that match existing coral δ^18O records from the tropical Pacific, with reduced amplitude of variability in the 1920s through the 1960s, a period of weak ENSO activity.

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Journal of Geophysical Research

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