Tree-ring stable oxygen isotope (δ¹⁸O_TR) is widely used for reconstructing past climate changes. However, the climate and circulation signals recorded by δ¹⁸O_TR are very complex and require accurate and reasonable mechanism explanations.

In southeastern China (SEC), δ¹⁸O_TR records were found significant reflections of both the local climate and El Niño–Southern Oscillation (ENSO) variations. However, the correlations between ENSO and local climate variations in SEC are insignificant, so the local climate variation in SEC cannot link the δ¹⁸O_TR with ENSO.

Based on meteorological data, precipitation oxygen isotope (δ¹⁸O_P) data, and Lagrangian backward trajectory experiments, a research group led by Prof. LIU Yu from the Institute of Earth Environment, Chinese Academy of Sciences (IEECAS) established a conceptual model explaining the effect pathway from ENSO to SEC δ¹⁸O_TR records.

This study was published in International Journal of Climatology on 06 March 2022.

The SEC δ¹⁸O_TR records are significantly positively correlated with ENSO of the previous winter, indicating that during the El Niño decaying years, the δ¹⁸O_TR values in SEC are prone to be high.

In the El Niño decaying years, convection weakens over the Northwest Pacific. The areas with weakening convection largely match the main moisture sources of SEC precipitation. Upstream convective weakening enriches ¹⁸O in moisture, increasing δ¹⁸O values in precipitation and thus tree-ring cellulose in SEC.

Researchers also denied that changes in moisture sources act as a factor in connecting SEC δ¹⁸O_TR records with ENSO.

This study helps to understand the climate significance of δ¹⁸O_P-related records in the East Asian monsoon region.

Contact: Bai Jie, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China. Email: baijie@ieecas.cn