Schwander et al. (1993)
Also: Schwander et al. 1993
The age of the air in the firn and the ice at Summit, Greenland
Schwander, J., Barnola, J. M., Andrié, C., Leuenberger, M., Ludin, A., Raynaud, D., & Stauffer, B. (1993). The age of the air in the firn and the ice at Summit, Greenland. Journal of Geophysical Research: Atmospheres, 98(D2), 2831-2838. Link to abstract.
DOI: 10.1029/92JD02383
References
All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.