 |
| Titel |
An assessment of the carbon balance of Arctic tundra: comparisons among observations, process models, and atmospheric inversions |
| VerfasserIn |
A. D. McGuire, T. R. Christensen, D. Hayes, A. Heroult, E. Euskirchen, J. S. Kimball, C. Koven, P. Lafleur, P. A. Miller, W. Oechel, P. Peylin, M. Williams, Y. Yi |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 8 ; Nr. 9, no. 8 (2012-08-17), S.3185-3204 |
| Datensatznummer |
250007242
|
| Publikation (Nr.) |
 copernicus.org/bg-9-3185-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| Although Arctic tundra has been estimated to cover only 8% of the global
land surface, the large and potentially labile carbon pools currently stored
in tundra soils have the potential for large emissions of carbon (C) under a
warming climate. These emissions as radiatively active greenhouse gases in
the form of both CO2 and CH4 could amplify global warming. Given
the potential sensitivity of these ecosystems to climate change and the
expectation that the Arctic will experience appreciable warming over the next
century, it is important to assess whether responses of C exchange in tundra
regions are likely to enhance or mitigate warming. In this study we compared
analyses of C exchange of Arctic tundra between 1990 and 2006 among
observations, regional and global applications of process-based terrestrial
biosphere models, and atmospheric inversion models. Syntheses of flux
observations and inversion models indicate that the annual exchange of
CO2 between Arctic tundra and the atmosphere has large uncertainties
that cannot be distinguished from neutral balance. The mean estimate from an
ensemble of process-based model simulations suggests that Arctic tundra has acted
as a sink for atmospheric CO2 in recent decades, but based on the
uncertainty estimates it cannot be determined with confidence whether these
ecosystems represent a weak or a strong sink. Tundra was 0.6 °C
warmer in the 2000s compared to the 1990s. The central estimates of the
observations, process-based models, and inversion models each identify
stronger sinks in the 2000s compared with the 1990s. Some of the process
models indicate that this occurred because net primary production increased
more in response to warming than heterotrophic respiration. Similarly, the
observations and the applications of regional process-based models suggest
that CH4 emissions from Arctic tundra have increased from the 1990s to
2000s because of the sensitivity of CH4 emissions to warmer
temperatures. Based on our analyses of the estimates from observations,
process-based models, and inversion models, we estimate that Arctic tundra
was a sink for atmospheric CO2 of 110 Tg C yr−1 (uncertainty
between a sink of 291 Tg C yr−1 and a source of 80 Tg C yr−1)
and a source of CH4 to the atmosphere of 19 Tg C yr−1
(uncertainty between sources of 8 and 29 Tg C yr−1). The suite of
analyses conducted in this study indicate that it is important to reduce
uncertainties in the observations, process-based models, and inversions in
order to better understand the degree to which Arctic tundra is influencing
atmospheric CO2 and CH4 concentrations. The reduction of
uncertainties can be accomplished through (1) the strategic placement of more
CO2 and CH4 monitoring stations to reduce uncertainties in
inversions, (2) improved observation networks of ground-based measurements of
CO2 and CH4 exchange to understand exchange in response to
disturbance and across gradients of climatic and hydrological variability,
and (3) the effective transfer of information from enhanced observation
networks into process-based models to improve the simulation of CO2 and
CH4 exchange from Arctic tundra to the atmosphere. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|