Stable isotope fingerprint of cold waves in atmospheric water vapor

Cold waves, characterized by the rapid cold air mass outbreaks and abrupt temperature drops, are becoming increasingly frequent and intense under global warming, posing severe threats to societies and ecosystems. While traditional research has relied largely on meteorological observations and numerical modeling, a substantial gap remains in understanding their stable isotopic signatures and underlying mechanisms. Here, we combine three consecutive winters of water vapor isotopic measurements in Shanghai with meteorological observations and isotope fractionation models to investigate isotopic fingerprints of cold wave events. We show that cold waves can imprint a reproducible isotopic signal, with concurrent δ¹⁸O depletion and deuterium excess (d) increase. This isotopic response is primarily driven by the synoptic-scale advection and mixing of dry, cold, isotopically depleted continental air masses, with temperature-dependent fractionation playing a secondary role. The magnitude of the isotopic response scales with cold wave intensity, depending on the configuration and strength of key circulation patterns, such as the Ural Blocking High/Siberian High and the East Asian Trough. These findings establish the coupled δ¹⁸O-d signature in water vapor or precipitation as a quantitative tracer for cold waves, complementing conventional meteorological diagnostics and providing a robust foundation for interpreting paleo-isotopic archives across East Asia.