Research ArticleCLIMATOLOGY

On the glacial-interglacial variability of the Asian monsoon in speleothem δ18O records

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Science Advances  12 Feb 2020:
Vol. 6, no. 7, eaay8189
DOI: 10.1126/sciadv.aay8189

Abstract

While Asian monsoon (AM) changes have been clearly captured in Chinese speleothem oxygen isotope (δ18O) records, the lack of glacial-interglacial variability in the records remains puzzling. Here, we report speleothem δ18O records from three locations along the trajectory of the Indian summer monsoon (ISM), a major branch of the AM, and characterize AM rainfall over the past 180,000 years. We have found that the records close to the monsoon moisture source show large glacial-interglacial variability, which then decreases landward. These changes likely reflect a stronger oxygen isotope fractionation associated with progressive rainout of AM moisture during glacial periods, possibly due to a larger temperature gradient and suppressed plant transpiration. We term this effect, which counteracts the forcing of glacial boundary conditions, the moisture transport pathway effect.

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