Global N2O cycle: Assessment of the global N2O budget based on seasonal and long-term isotope measurements at Jungfraujoch and the Cape Grim Air Archive

Scientist Empa: Dr. Longfei Yu (Postdoc)

Collaboration with Dr. Paul Krummel (CSIRO, Australia), Dr. Eliza Harris (University of Innsbruck, Austria)


The aim of this SNSF funded project is to assess the global N2O budget by providing for the first time high-precision data (δ15Nα, δ15Nβ, δ18O; ≤ 0.1‰) showing seasonal and interannual changes in the site-specific N2O isotopic composition, followed by a modelling approach for data interpretation and up-scaling. We propose to measure long-term trends and interannual variability using 30 years of archived air samples from the Cape Grim Air Archive, Australia. In addition, seasonal and intra-annual variability will be examined at higher temporal resolution over two years based on flask sampling at remote measuring stations in the southern (Cape Grim, monthly sampling) and northern (Jungfraujoch, weekly sampling) hemispheres. Concentration and isotopic composition analyses for all samples will be carefully calibrated to ensure traceability and comparability with other studies into the future.

The isotopic data will be interpreted using various box modelling approaches to identify in particular changes in the isotopic signature of N2O from anthropogenic sources, as well as variations in sources and sinks responsible for seasonality and interannual variability. These results will be used to address three major research questions:

  • Has the global anthropogenic source isotopic signature changed over the past 30 years? How does this reflect changes in source identity and climate?
  • What is the difference in N2O isotopic composition between the northern and southern hemispheres, in particular isotopic site preference? Does this agree with expectations based on hemispheric source estimates?
  • What can isotopic composition changes tell us about the major drivers of seasonality and interannual variability in N2O mixing ratio and growth rate?


This study will improve our understanding of the global N2O cycle, advancing model approaches for predicting the response of N2O emissions to climate and societal changes in the coming decades. These results will benefit the policy makers in planning mitigation strategies for global N2O emissions.

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