High Ozone Isotope Anomaly at Mt. Everest Linked to Stratospheric Ozone Intrusion

Atmospheric O 3 possesses a rare isotopic signal, that is, Δ 17 O(O 3 ), varying with pressure and temperature, providing a potential tracer to explore stratosphere‐to‐troposphere transport (STT) of O 3 that plays a vital role in atmospheric chemistry and climate. However, it has been proposed that the higher stratospheric Δ 17 O(O 3 ) can't be preserved en‐route to the troposphere given the rapidly re‐established isotopic equilibrium by photochemistry. Here, we reported Δ 17 O(O 3 ) data mainly from the Tibetan Plateau, and found the relatively high Δ 17 O(O 3 ) at Mt. Everest can't be explained by in situ photochemistry. Instead, the distinct diurnal cycle with elevated nighttime value at Mt. Everest is associated with the katabatic wind bringing stratosphere‐sourced O 3 with high Δ 17 O. This demonstrates that the high Δ 17 O(O 3 ) can be preserved at troposphere at some circumstances. Given the fast transfer of Δ 17 O(O 3 ) to atmospheric nitrate, it might be potential to probe past STT of O 3 using nearby ice core records of nitrate.