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| Titel |
Use of a New Low-Power Laser-Based Instrumentation to Measure Methane Emissions from Remote Permafrost Regions |
| VerfasserIn |
George Burba, Cove Sturtevant, Olli Peltola, Peter Schreiber, Rommel Zulueta, Sami Haapanala, Ivan Mammarella, Janne Rinne, Timo Vesala, Dayle McDermitt, Walt Oechel |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250071734
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| Zusammenfassung |
| The permafrost regions store significant amount 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 following decades and
centuries.
Present measurements of methane fluxes in permafrost regions have mostly 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 remote or portable research in cold
regions. 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 (hourly to annual). 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, climate control, and analyzer systems. 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 in cold
regions 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 instrumentation allows methane flux measurements at normal
pressure without a need for a pump. As a result, the measurements can be done
with very low-power (e.g., 7-10 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 station is important for number of
ecosystems (rice fields, landfills, wetlands, cattle yards, etc.), but it is especially
important for permafrost and other cold regions where grid power and access roads
are generally not available, and logistics of running the experiment is particularly
expensive.
Emerging research using low-power laser-based instrumentation to measure CH4
emissions are presented from several permafrost ecosystems with contrasting setups,
weather, and moisture conditions. Principles of open-path instrument operation,
station characteristics and requirements are also discussed, as well as concurrent
measurements of CO2 and H2O emissions using open-path and enclosed instrumentation. |
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