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| Titel |
Methane Emissions from Permafrost Regions using Low-Power Eddy Covariance Stations |
| VerfasserIn |
G. Burba, C. Sturtevant, P. Schreiber, O. Peltola, R. Zulueta, I. Mammarella, S. Haapanala, J. Rinne, T. Vesala, D. McDermitt, W. Oechel |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250059069
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| Zusammenfassung |
| Methane is an important greenhouse gas with a warming potential 23 times that of carbon dioxide over a 100-year cycle. The permafrost regions of the world store significant amounts of organic materials under anaerobic conditions, leading to large methane production and accumulation in the upper layers of bedrock, soil and ice. These regions are currently undergoing dramatic change in response to warming trends, and may become a significant potential source of global methane release under a warming climate over the coming decades and centuries.
Presently, most measurements of methane fluxes in permafrost regions have been made with static chamber techniques, and very few were done with the eddy covariance approach using closed-path analyzers. Although chambers and closed-path analyzers have advantages, both techniques have significant limitations, especially for permafrost research. Static chamber measurements are discrete in time and space, and particularly difficult to use over polygonal tundra with highly non-uniform micro-topography and active water layer. They also may not capture the dynamics of methane fluxes on varying time scales (hours to annual estimates). In addition, placement of the chamber may disturb the surface integrity causing a significant over-estimation of the measured flux.
Closed-path gas analyzers for measuring methane eddy fluxes employ advanced technologies such as TDLS (Tunable Diode Laser Spectroscopy), ICOS (Integrated Cavity Output Spectroscopy), WS-CRDS (wavelength scanned cavity ring-down spectroscopy), but require high flow rates at significantly reduced optical cell pressures to provide adequate response time and sharpen absorption features. Such methods, when used with the eddy covariance technique, require a vacuum pump and a total of 400-1500 Watts of grid power for the pump and analyzer system. The weight of such systems often exceeds 100-200 lbs, restricting practical applicability for remote or portable field studies.
As a result, spatial coverage of eddy covariance methane flux measurements remains limited. Remote permafrost wetlands of Arctic tundra, northern boreal peatlands of Canada and Siberia, and other highly methanogenic ecosystems have few eddy covariance methane measurement stations. Those existing are often located near grid power sources and roads rather than in the middle of the methane-producing ecosystem, while those that are placed appropriately may require extraordinary efforts to build and maintain them, with large investments into man-power and infrastructure.
Alternatively, open-path approach allows methane flux measurements at ambient pressure without the need for a pump. As a result, the measurements can be done with very low-power (e.g. 5-10 Watts), light (5 .2 kg) instruments permitting solar- and wind- powered remote deployments in hard-to-reach sites from permanent, portable or mobile stations, and cost-effective additions of a methane measurement to the present array of CO2 and H2O measurements.
The low-power operation and light weight of open-path eddy covariance stations is important for a number of ecosystems (rice fields, landfills, wetlands, cattle yards), but it is especially important for permafrost regions where grid power and access roads are generally not available, and the logistics of running the experiments are particularly expensive.
Emerging research on methane flux measurements using low-power stations equipped with LI-7700 open-path methane analyzer (LI-COR Biosciences) are presented from several permafrost ecosystems with contrasting setups, and weather conditions. Principles of operation, station characteristics and requirements are also discussed. |
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