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| Titel |
Application of a methane carbon isotope analyzer for the investigation of δ¹³C of methane emission measured by the automatic chamber method in an Arctic Tundra |
| VerfasserIn |
Mikhail Mastepanov, Torben Christensen |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092018
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| Publikation (Nr.) |
 EGU/EGU2014-6341.pdf |
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| Zusammenfassung |
| Methane emissions have been monitored by an automatic chamber method in Zackenberg
valley, NE Greenland, since 2006 as a part of Greenland Ecosystem Monitoring (GEM)
program. During most of the seasons the measurements were carried out from the time of
snow melt (June-July) until freezing of the active layer (October-November). Several years of
data, obtained by the same method, instrumentation and at exactly the same site, provided a
unique opportunity for the analysis of interannual methane flux patterns and factors affecting
their temporal variability.
The start of the growing season emissions was found to be closely related to a date of
snow melt at the site. Despite a large between year variability of this date (sometimes more
than a month), methane emission started within a few days after, and was increasing for the
next about 30 days. After this peak of emission, it slowly decreased and stayed more or less
constant or slightly decreasing during the rest of the growing season (Mastepanov et
al., Biogeosciences, 2013). During the soil freezing, a second peak of methane
emission was found (Mastepanov et al., Nature, 2008); its amplitude varied a lot
between the years, from almost undetectable to comparable with total growing season
emissions.
Analysis of the multiyear emission patterns (Mastepanov et al., Biogeosciences, 2013) led
to hypotheses of different sources for the spring, summer and autumn methane
emissions, and multiyear cycles of accumulation and release of these components to the
atmosphere.
For the further investigation of this it was decided to complement the monitoring system
with a methane carbon isotope analyzer (Los Gatos Research, USA). The instrument was
installed during 2013 field season and was successfully operating until the end of the
measurement campaign (27 October). Detecting both 12C-CH4 and 13C-CH4 concentrations
in real time (0.5 Hz) during automatic chamber closure (15 min), the instrument was
providing data for determination of δ13C of the emitting methane (by a relation between
12C-CH4 and 13C-CH4 fluxes).
Unfortunately, the beginning of the season was missed due to a delay in the instrument
shipment; the summer fluxes were lower than any of the 7 previous years due to an
exceptional drought; the autumn burst was not detected due to both exceptionally slow soil
freezing and a low soil methane content. However, the data obtained from the most
productive chambers confirm the feasibility of the chosen method and give good expectations
for the following field campaign 2014. |
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