Work

Remote Indo-South Pacific as the primary upstream control on East Asian precipitation isotopes

Year: 2026

Type: article

Abstract: Deciphering speleothem oxygen isotope records in the East Asian monsoon region is critical for understanding hydroclimate variability, yet the role of upstream effects remains poorly quantified. Here, we combine an isotope-enabled atmospheric model with water-tagging capability and a backtracking algorithm to develop a physically based precipitation-weighted Upstream Accumulated Precipitation (weighted-UAP) index that quantifies the impact of upstream effects on East Asian precipitation δ 18 O. Our framework reveals that Indo-South Pacific moisture, despite contributing only a small fraction of total precipitation, accounts for up to 46% of the interannual variance in East Asian precipitation δ 18 O, as it acquires a strong depleted isotope signal through extensive fractionation during transport. Specifically, the negative East Asian precipitation δ 18 O anomaly is primarily driven by enhanced Tropical Southern Pacific Ocean (TSPO) moisture contribution, facilitated by a La Niña-like South Pacific anticyclone. Concurrently, the Indian Ocean (IO) moisture amplifies this isotopic depletion through a coupled increase in both enroute precipitation and moisture source contributions. This framework further elucidates the non-stationary relationship between ENSO and East Asian precipitation δ 18 O arises from asynchronous changes in ENSO and the Indian Summer Monsoon. Our findings provide a novel perspective for interpreting speleothem δ 18 O and associated hydroclimate changes.

Source: npj Climate and Atmospheric Science

DOI: 10.1038/s41612-026-01443-3

Authors: Yuan Gao, Jun Hu, Risheng Liang, Shutao Cao

Institution: Xiamen University

Language: English

Topic: Climate variability and models

Subfield: Global and Planetary Change

Field: Environmental Science

Domain: Physical Sciences

SDG: Climate action

Open Access status: gold

Estimated APC paid: $3,590