Decoupling of Monsoon Dynamics and Thermodynamics Under Global Warming: Evidence From Multi-Proxy Records in a Single Speleothem

Abstract

Speleothem multiproxy records are important for understanding the differences between the dynamic and thermodynamic aspects of the Asian summer monsoon. In this study, we simultaneously provide the seasonally resolved oxygen isotope (δ¹⁸O_s) and trace element ratio (Mg/Ca, Sr/Ca, and Ba/Ca) records from an actively growing stalagmite from Zhangjia Cave, Sichuan Basin, southwestern China, covering the past ∼130 years. The overall increasing trend in δ¹⁸O_s indicates a weakening of Asian summer monsoon circulation over the last century, while the trace element ratios suggest a relatively stable precipitation trend. Notably, the correlation between δ¹⁸O_s and trace element ratios has experienced a significant transition since the acceleration of global warming from the 1970s. Our findings reinforce the notion that the forcing of greenhouse gases weakened monsoon dynamics (circulation) over the past century, whereas the monsoon thermodynamic (precipitation) was essentially unchanged, thus highlighting the different influences of the greenhouse gases on the monsoon dynamics and thermodynamics, respectively.