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| Titel |
Revisiting factors controlling methane emissions from high-Arctic tundra |
| VerfasserIn |
M. Mastepanov, C. Sigsgaard, T. Tagesson, L. Ström, M. P. Tamstorf, M. Lund, T. R. Christensen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-30), S.5139-5158 |
| Datensatznummer |
250018367
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| Publikation (Nr.) |
 copernicus.org/bg-10-5139-2013.pdf |
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| Zusammenfassung |
| The northern latitudes are experiencing disproportionate warming relative to
the mid-latitudes, and there is growing concern about feedbacks between this
warming and methane production and release from high-latitude soils. Studies
of methane emissions carried out in the Arctic, particularly those with
measurements made outside the growing season, are underrepresented in the
literature. Here we present results of 5 yr (2006–2010) of automatic
chamber measurements at a high-Arctic location in Zackenberg, NE Greenland,
covering both the growing seasons and two months of the following freeze-in
periods. The measurements show clear seasonal dynamics in methane emission.
The start of the growing season and the increase in CH4 fluxes were
strongly related to the date of snowmelt. Within each particular growing
season, CH4 fluxes were highly correlated with the soil temperature
(R2 > 0.75), which is probably explained by high seasonality of both
variables, and weakly correlated with the water table. The greatest
variability in fluxes between the study years was observed during the first
part of the growing season. Somewhat surprisingly, this variability could not
be explained by commonly known factors controlling methane emission, i.e.
temperature and water table position. Late in the growing season CH4
emissions were found to be very similar between the study years (except the
extremely dry 2010) despite large differences in climatic factors
(temperature and water table). Late-season bursts of CH4 coinciding
with soil freezing in the autumn were observed during at least three years.
The cumulative emission during the freeze-in CH4 bursts was comparable
in size with the growing season emission for the year 2007, and about one
third of the growing season emissions for the years 2009 and 2010. In all
three cases the CH4 burst was accompanied by a corresponding episodic
increase in CO2 emission, which can compose a significant contribution
to the annual CO2 flux budget. The most probable mechanism of the
late-season CH4 and CO2 bursts is physical release of gases
accumulated in the soil during the growing season. In this study we discuss
possible links between growing season and autumn fluxes. Multiannual dynamics
of the subsurface CH4 storage pool are hypothesized to be such a link
and an important driver of intearannual variations in the fluxes, capable of
overruling the conventionally known short-term control factors (temperature
and water table). Our findings suggest the importance of multiyear studies
with a continued focus on shoulder seasons in Arctic ecosystems. |
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