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| Titel |
Methane emission bursts from permafrost environments during autumn freeze-in: new insights from ground penetrating radar |
| VerfasserIn |
Norbert Pirk, Telmo Santos, Carl Gustafson, Anders J. Johansson, Fredrik Tufvesson, Frans-Jan W. Parmentier, Mikhail Mastepanov, Torben R. Christensen |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127217
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| Publikation (Nr.) |
 EGU/EGU2016-7067.pdf |
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| Zusammenfassung |
| Large amounts of methane (CH4) are known to be emitted from permafrost environments
during the autumn freeze-in, but the specific soil conditions leading up to these bursts are
unclear. We therefore assessed the possibility to complement surface flux measurements with
ground penetrating radar (GPR), which can estimate the amounts of ice, water and gas in the
soil through their different dielectric properties. We developed an ultra-wide band (UWB)
transmission GPR setup operating in the frequency range from 200 to 3200 MHz,
which was tested in laboratory experiments on a soil sample during an induced
freeze-thaw cycle, and applied in a field campaign in Northeast Greenland during autumn
2009.
In the laboratory case, the GPR signals captured the same dynamics as the surface CH4
flux, featuring a series of large and sharp peaks during the thawing phase of the experiment.
The CH4 emission peak during the freezing period, however, could not be reproduced in this
laboratory experiment.
The results of our field campaign suggest a compression of the gas reservoir during the
freezing period in the autumn, which is accompanied by a peak in surface CH4 emissions.
About one week thereafter, there seemed to be a decompression event, consistent with
ground cracking which allows the gas reservoir to expand again. This coincided
with the largest CH4 emission, exceeding the summer maximum by a factor of
4.
We argue that subsurface GPR measurements open new possibilities to come to an
understanding of tundra CH4 bursts connected to soil freezing. |
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