Variations of surface and subsurface conditions after tundra fire in Seward Peninsula, Alaska
Abstract
In Seward Peninsula, southwest Alaska, large tundra fires in 1971 and 2002 burned a wide area underlain by discontinuous permafrost near the Kougarok River. Fires destroyed the vegetation, and the ground surface thermal condition was altered. The research objective is to understand the characteristics of the post-fire variations in permafrost distribution and condition, and the attributional changes in thermal and water conditions in active layer. Field observations were conducted at burned and unburned sites in summer since 2005. The identical measurements were made at the sites for each of north- and south-facing slopes. The thermal and water conditions were compared with each other. Thaw depths at burned sites are deeper by 30-40 % than those at unburned sites. Differences of thaw depth seem to decrease year by year. Apparent electrical resistivity obtained from electrical soundings up to 1m deep in 2006, 2007 and 2012 showed that the resistivity values at burned sites were lower than those at unburned sites. As an apparent resistivity value of a layer is generally a function of the true resistivity value and its thickness, a simple calculation was carried out in order to estimate a true resistivity value of unfrozen mineral soil in the active layer. The calculated results showed higher true resistivity at burned sites than at unburned sites, which correspond well to the measured relatively lower water condition. It was also shown that resistivity values at burned sites had small variations between 2006 and 2007, which may be due to small variations in soil water, and suggest resetting of water conditions by wild fires.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.C13C0632H
- Keywords:
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- 0702 CRYOSPHERE / Permafrost