American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 458426 bytes)    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D1, 8148, doi:10.1029/2001JD000438, 2003

Impacts of wildfire on the permafrost in the boreal forests of Interior Alaska

Kenji Yoshikawa

Water and Environmental Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA


William R. Bolton

Water and Environmental Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA


Vladimir E. Romanovsky

Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA


Masami Fukuda

Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan


Larry D. Hinzman

Water and Environmental Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA


Abstract

The impact to the permafrost during and after wildfire was studied using 11 boreal forest fire sites including two controlled burns. Heat transfer by conduction to the permafrost was not significant during fire. Immediately following fire, ground thermal conductivity may increase 10-fold and the surface albedo can decrease by 50% depending on the extent of burning of the surficial organic soil. The thickness of the remaining organic layer strongly affects permafrost degradation and aggradation. If the organic layer thickness was not reduced during the burn, then the active layer (the layer of soil above permafrost that annually freezes and thaws) did not change after the burn in spite of the surface albedo decrease. Any significant disturbance to the surface organic layer will increase heat flow through the active layer into the permafrost. Approximately 3–5 years after severe disturbance and depending on site conditions, the active layer will increase to a thickness that does not completely refreeze the following winter. This results in formation of a talik (an unfrozen layer below the seasonally frozen soil and above the permafrost). A thawed layer (4.15 m thick) was observed at the 1983 burned site. Model studies suggest that if an organic layer of more than 7–12 cm remains following a wildfire then the thermal impact to the permafrost will be minimal in the boreal forests of Interior Alaska.

Published 18 December 2002.

Index Terms: 1823 Hydrology: Frozen ground; 0614 Electromagnetics: Biological effects; 1866 Hydrology: Soil moisture.

Read Full Article (file size: 458426 bytes)    Cited by

Citation: Yoshikawa, K., W. R. Bolton, V. E. Romanovsky, M. Fukuda, and L. D. Hinzman (2002), Impacts of wildfire on the permafrost in the boreal forests of Interior Alaska, J. Geophys. Res., 107, 8148, doi:10.1029/2001JD000438, [printed 108(D1), 2003].