Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks : results from an atmosphere-ocean general circulation model
Thornton, Peter E.
Doney, Scott C.
Moore, J. Keith
Mahowald, Natalie M.
Randerson, James T.
Fung, Inez Y.
Feddema, J. J.
MetadataShow full item record
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.
© 2009 The Authors. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 6 (2009): 2099-2120, doi:10.5194/bg-6-2099-2009
The following license files are associated with this item:
Except where otherwise noted, this item's license is described as http://creativecommons.org/licenses/by/3.0/
Showing items related by title, author, creator and subject.
Atmospheric carbon dioxide variability in the Community Earth System Model : evaluation and transient dynamics during the twentieth and twenty-first centuries Keppel-Aleks, Gretchen; Randerson, James T.; Lindsay, Keith; Stephens, Britton B.; Moore, J. Keith; Doney, Scott C.; Thornton, Peter E.; Mahowald, Natalie M.; Hoffman, Forrest M.; Sweeney, Colm; Tans, Pieter P.; Wennberg, Paul O.; Wofsy, Steven C. (American Meteorological Society, 2013-07-01)Changes in atmospheric CO2 variability during the twenty-first century may provide insight about ecosystem responses to climate change and have implications for the design of carbon monitoring programs. This paper describes ...
McKinley, Galen A.; Takahashi, Taro; Buitenhuis, Erik T.; Chai, Fei; Christian, James R.; Doney, Scott C.; Jiang, Mingshun; Lindsay, Keith; Moore, J. Keith; Le Quere, Corinne; Lima, Ivan D.; Murtugudde, Raghu; Shi, L.; Wetzel, P. (American Geophysical Union, 2006-07-04)Climate variability drives significant changes in the physical state of the North Pacific, and thus there may be important impacts of climate variability on the upper ocean carbon balance across the basin. We address this ...
Randerson, James T.; Lindsay, Keith; Munoz, E.; Fu, W.; Moore, J. Keith; Hoffman, Forrest M.; Mahowald, Natalie M.; Doney, Scott C. (John Wiley & Sons, 2015-06-02)Improved constraints on carbon cycle responses to climate change are needed to inform mitigation policy, yet our understanding of how these responses may evolve after 2100 remains highly uncertain. Using the Community Earth ...