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| Titel |
Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks: results from an atmosphere-ocean general circulation model |
| VerfasserIn |
P. E. Thornton, S. C. Doney, K. Lindsay, J. K. Moore, N. Mahowald, J. T. Randerson, I. Fung, J.-F. Lamarque, J. J. Feddema, Y.-H. Lee |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 6, no. 10 ; Nr. 6, no. 10 (2009-10-08), S.2099-2120 |
| Datensatznummer |
250004033
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| Publikation (Nr.) |
 copernicus.org/bg-6-2099-2009.pdf |
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| Zusammenfassung |
| Inclusion of fundamental ecological interactions between carbon and nitrogen
cycles in the land component of an atmosphere-ocean general circulation
model (AOGCM) leads to decreased carbon uptake associated with CO2
fertilization, and increased carbon uptake associated with warming of the
climate system. The balance of these two opposing effects is to reduce the
fraction of anthropogenic CO2 predicted to be sequestered in land
ecosystems. The primary mechanism responsible for increased land carbon
storage under radiatively forced climate change is shown to be fertilization
of plant growth by increased mineralization of nitrogen directly associated
with increased decomposition of soil organic matter under a warming climate,
which in this particular model results in a negative gain for the
climate-carbon feedback. Estimates for the land and ocean sink fractions of
recent anthropogenic emissions are individually within the range of
observational estimates, but the combined land plus ocean sink fractions
produce an airborne fraction which is too high compared to observations.
This bias is likely due in part to an underestimation of the ocean sink
fraction. Our results show a significant growth in the airborne fraction of
anthropogenic CO2 emissions over the coming century, attributable in
part to a steady decline in the ocean sink fraction. Comparison to
experimental studies on the fate of radio-labeled nitrogen tracers in
temperate forests indicates that the model representation of competition
between plants and microbes for new mineral nitrogen resources is
reasonable. Our results suggest a weaker dependence of net land carbon flux
on soil moisture changes in tropical regions, and a stronger positive growth
response to warming in those regions, than predicted by a similar AOGCM
implemented without land carbon-nitrogen interactions. We expect that the
between-model uncertainty in predictions of future atmospheric CO2
concentration and associated anthropogenic climate change will be reduced as
additional climate models introduce carbon-nitrogen cycle interactions in
their land components. |
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