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Sensitivity analysis of a model of CO2 exchange in tundra ecosystems by the adjoint methodA model of net primary production (NPP), decomposition, and nitrogen cycling in tundra ecosystems has been developed. The adjoint technique is used to study the sensitivity of the computed annual net CO2 flux to perturbation in initial conditions, climatic inputs, and model's main parameters describing current seasonal CO2 exchange in wet sedge tundra at Barrow, Alaska. The results show that net CO2 flux is most sensitive to parameters characterizing litter chemical composition and more sensitive to decomposition parameters than to NPP parameters. This underlines the fact that in nutrient-limited ecosystems, decomposition drives net CO2 exchange by controlling mineralization of main nutrients. The results also indicate that the short-term (1 year) response of wet sedge tundra to CO2-induced warming is a significant increase in CO2 emission, creating a positive feedback to atmosphreic CO2 accumulation. However, a cloudiness increase during the same year can severely alter this response and lead to either a slight decrease or a strong increase in emitted CO2, depending on its exact timing. These results demonstrate that the adjoint method is well suited to study systems encountering regime changes, as a single run of the adjoint model provides sensitivities of the net CO2 flux to perturbations in all parameters and variables at any time of the year. Moreover, it is shown that large errors due to the presence of thresholds can be avoided by first delimiting the range of applicability of the adjoint results.
Document ID
19950044646
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Waelbroek, C.
(Lab. de Modelisation du Climat et de l'Environnement Gif-sur-Yvette, Fran, United States)
Louis, J.-F.
(Atmospheric and Environmental Research, Inc. Cambridge, MA, United States)
Date Acquired
August 16, 2013
Publication Date
February 20, 1995
Publication Information
Publication: Journal of Geophysical Research
Volume: 100
Issue: D2
ISSN: 0148-0227
Subject Category
Meteorology And Climatology
Accession Number
95A76245
Funding Number(s)
CONTRACT_GRANT: NGT-30057
CONTRACT_GRANT: DE-FG02-90ER-61065
Distribution Limits
Public
Copyright
Other

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