Reinterpreting precipitation isotope records from Asian monsoon region through the hidden role of atmospheric updraft

Speleothem oxygen isotope records (δ 18 O s ) from the Asian monsoon region provide valuable insights into past hydroclimate variability, yet their interpretation relies on understanding the controls on modern precipitation isotopes (δ 18 O p ). Although numerous explanations for the spatiotemporal variability of δ 18 O p across this region have been proposed, the primary controls remain unresolved. Here we propose a hypothesis to explain δ 18 O p variability from δ 18 O p records at 46 sites along a transect spanning the Asian monsoon region. Our results show that seasonally low δ 18 O p values migrate gradually westward along the east–west transect. We further demonstrate that the corresponding westward migration of atmospheric updraft, particularly convection, controls δ 18 O p variations along the transect. In contrast to previous interpretations emphasizing monsoon moisture advection, our findings highlight atmospheric updraft as an important control on δ 18 O p variations across the Asian monsoon region. These findings provide an alternative perspective on interpreting the climate signals preserved in Asian δ 18 O s records.