This work was carried out under the auspices of the GeoBasis programme and part of the Zackenberg Ecological Research Operations funded by the Danish Ministry of the Environment and the ISICaB project funded by the Commission for Scientific Research in Greenland (KVUG). ASIAQ–Greenland Survey provided climate data. The work was also supported by the Swedish Research Councils VR and FORMAS. We thank P. Bergamachi (JRC) and J.-F. Meirink (KNMI) for providing the TM5 model setup. T. Tagesson helped with the field work in Zackenberg. We are grateful for comments on earlier versions of this manuscript from A. Lindroth and B. Christensen.

Author Contributions T.R.C., M.P.T., M.M., C.S. and L.S. designed the field research; M.M. designed, constructed and set up the automatic measurement system in Zackenberg; C.S. operated the system and performed manual measurements; M.M. performed data analysis; E.D. and S.H. provided atmospheric CH 4 data and designed and ran the atmospheric transport model experiments; T.R.C., M.M., S.H. and E.D. drafted the manuscript.