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| Titel |
Frozen ponds: production and storage of methane during the Arctic winter in a lowland tundra landscape in northern Siberia, Lena River delta |
| VerfasserIn |
M. Langer, S. Westermann, K. Walter Anthony, K. Wischnewski, J. Boike |
| 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 ; 12, no. 4 ; Nr. 12, no. 4 (2015-02-17), S.977-990 |
| Datensatznummer |
250117819
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| Publikation (Nr.) |
 copernicus.org/bg-12-977-2015.pdf |
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| Zusammenfassung |
Lakes and ponds play a key role in the carbon cycle of permafrost ecosystems,
where they are considered to be hotspots of carbon dioxide CO2 and
methane CH4 emission. The strength of these emissions is, however,
controlled by a variety of physical and biogeochemical processes whose
responses to a warming climate are complex and only poorly understood. Small
waterbodies have been attracting an increasing amount of attention since
recent studies demonstrated that ponds can make a significant contribution to
the CO2 and CH4emissions of tundra ecosystems. Waterbodies
also have a marked effect on the thermal state of the surrounding permafrost;
during the freezing period they prolong the period of time during which
thawed soil material is available for microbial decomposition.
This study presents net CH4 production rates during the freezing
period from ponds within a typical lowland tundra landscape in northern
Siberia. Rate estimations were based on CH4 concentrations measured
in surface lake ice from a variety of waterbody types. Vertical profiles
along ice blocks showed an exponential increase in CH4 concentration
with depth. These CH4 profiles were reproduced by a 1-D mass balance
model and the net CH4 production rates were then inferred through
inverse modeling.
Results revealed marked differences in early winter net CH4
production among various ponds. Ponds situated within intact polygonal ground
structures yielded low net production rates, of the order of 10-11 to
10-10 mol m-2 s-1 (0.01 to 0.14 mgCH4 m-2 day-1). In contrast, ponds exhibiting
clear signs of erosion yielded net CH4 production rates of the order
of 10-7 mol m-2 s-1 (140 mg CH4 m-2 day-1). Our
results therefore indicate that once a particular threshold in thermal
erosion has been crossed, ponds can develop into major CH4 sources.
This implies that any future warming of the climate may result in nonlinear
CH4 emission behavior in tundra ecosystems. |
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