Trends and seasonal cycles in the isotopic composition of nitrous oxide since 1940

• Main Authors: S. Park, P. Croteau, K. A. Boering, D. M. Etheridge, D. Ferretti, P. J. Fraser, K-r. Kim, P. B. Krummel, R. L. Langenfelds, T. D. Van Ommen, L. P. Steele, C. M. Trudinger
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2012
• Subjects: Grim; Antarc*; Antarctica
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.360.9954; http://www.nature.com/ngeo/journal/v5/n4/pdf/ngeo1421.pdf

The atmospheric nitrous oxide mixing ratio has increased by 20 % since 1750 (ref. 1). Given that nitrous oxide is both a long-lived greenhouse gas2 and a stratospheric ozonedepleting substance3, this increase is of global concern. However, the magnitude and geographic distribution of nitrous oxide sources, and how they have changed over time, is uncertain4,5. A key unknown is the influence of the stratospheric circulation4,5, which brings air depleted in nitrous oxide to the surface. Here, we report the oxygen and intramolecular nitrogen isotopic compositions of nitrous oxide in firn air samples from Antarctica and archived air samples from Cape Grim, Tasmania, spanning 1940–2005. We detect seasonal cycles in the isotopic composition of nitrous oxide at Cape Grim. The phases and amplitudes of these seasonal cycles allow us to distinguish between the