ABSTRUCT
Thermal, water and electrical conditions of permafrost after the tundra fire were observed in Seward Peninsula, southwest Alaska, in order to evaluate the effect of fire on permafrost conditions. Field observations were made in 2005 and four sites were established where the slope direction and surfa...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.578.3638 http://www.iarc.uaf.edu/workshops/terrestrial_team/indiv_pdf/permafrost_degradation_after_tundra_fire.pdf |
| Summary: | Thermal, water and electrical conditions of permafrost after the tundra fire were observed in Seward Peninsula, southwest Alaska, in order to evaluate the effect of fire on permafrost conditions. Field observations were made in 2005 and four sites were established where the slope direction and surface disturbance condition are different; south- or north-facing, and burned or unburned. At each site ground temperature and water content were measured by pit survey, and the seasonal thawed depth measurements were also conducted by using the steel rod from the ground surface. Transient electromagnetic surveys were carried out along profiles with the length of 140-180m to compare the permafrost condition using a transmitter loop of 60 x 60m. The temperatures of 20-40cm deep at the burned sites were 4-5 ºC higher than that at the unburned sites. The soil water contents at the burned sites showed the high condition. The measured thawed depths are significantly different between the burned and unburned sites, which were more than 20cm deeper in the burned sites than that in the unburned sites. The obtained apparent resistivity curves and estimated resistivity models showed that a significant difference was observed between south- and north-facing slopes. At the north-facing sites, high resistivity layers were estimated near the ground surface with the thickness of 20-26m, which represents permafrost. The permafrost base could not be detected at the south-facing sites because the base is located in bedrock. There is no significant difference of the curves and models between burned and unburned sites. However, only at the burned south-facing site, stable data could be obtained by using the standard central induction configuration, which means that this site has a relative low resistivity condition near the ground surface. Thus, the burned south-facing site may have a different permafrost condition near the surface. |
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