Climate Science

A Record of Holocene N2O

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Science  08 Mar 2002:
Vol. 295, Issue 5561, pp. 1797
DOI: 10.1126/science.295.5561.1797a

Carbon dioxide, methane, and nitrous oxide are the three most radiatively important trace greenhouse gases, and their atmospheric concentrations contain important clues to biogeochemistry. Furthermore, knowing how their abundances have varied during preindustrial times is essential for understanding their modern behavior. Detailed records of CO2 and CH4 across the Holocene (the 11,000 years of relatively warm climate that have followed the last deglaciation) have been extracted from polar ice, but a similarly resolved chronicle of N2O has not been available.

Flückiger et al. present such a record, using ice from the European Project for Ice Coring in Antarctica Dome C core, in conjunction with parallel determinations of CO2 and CH4 from the same samples. They find that a minimum in the abundance of preanthropogenic N2O occurred about 8000 years ago, approximately coincident with the minimum for CO2. On the other hand, the long-term N2O variability during the Holocene was only half as great as the change during the period of deglaciation and less than a quarter as large as the recent anthropogenic increase. These results provide a framework for further studies, including isotopic measurements and better models of the nitrogen cycle in the terrestrial biosphere and the oceans (the predominant sources), that will help determine the causes of the observed variations in the concentration of atmospheric N2O (the primary sink). — HJS

Global Biogeochem. Cycles, 10.1029/2001GB001417 (2002).

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