Carbon Dioxide and Oxygen Isotope Anomalies in the Mesosphere and Stratosphere

Isotopic (δ 17 O and δ 18 O) measurements of stratospheric and mesospheric carbon dioxide (CO 2 ) and oxygen (O 2 ), along with trace species concentrations (N 2 O, CO, and CO 2 ), were made in samples collected from a rocket-borne cryogenic whole air sampler. A large mass-independent isotopic anomaly was observed in CO 2 , which may in part derive from photochemical coupling to ozone (O 3 ). The data also require an additional isotopic fractionation process, which is presently unidentified. Mesospheric O 2 isotope ratios differed from those in the troposphere and stratosphere. The cause of this isotopic variation in O 2 is presently unknown. The inability to account for these observations represents a fundamental gap in the understanding of the O 2 chemistry in the stratosphere and mesosphere.