Methane emission bursts from permafrost environments during autumn freeze-in: New insights from ground-penetrating radar

• Published in: Geophysical Research Letters
• Main Authors: Pirk, Norbert, Santos, Telmo, Gustafson, Carl, Johansson, Anders J, Tufvesson, Fredrik, Parmentier, Frans-Jan, Mastepanov, Mikhail, Christensen, Torben
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2015
• Subjects: Geosciences; Multidisciplinary; Electrical Engineering; Electronic Engineering; Information Engineering; ground-penetrating radar; Greenland; autumn freeze-in; methane; frequency domain; permafrost; Tundra
• Online Access: https://lup.lub.lu.se/record/7766980; https://doi.org/10.1002/2015GL065034

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. Therefore, we used an ultrawide band ground-penetrating radar in Northeast Greenland in autumn 2009 to estimate the volumetric composition inside the soil through dielectric characterization from 200 to 3200 MHz. Our results suggest a compression of the gas reservoir during the phase transition of soil water, which is accompanied by a peak in surface CH4 emissions. About 1 week thereafter, there seems to be a decompression event, consistent with ground cracking which allows the gas reservoir to expand again. This coincides with the largest CH4 emission, exceeding the summer maximum by a factor of 4. We argue that these complementary measurement techniques are needed to come to an understanding of tundra CH4 bursts connected to soil freezing.