Study finds that peat, vegetation help reduce permafrost thaw
Found in arctic regions, permafrost is frozen soil that remains at or below 0 C for at least two consecutive years. Permafrost covers more than 30 per cent of the Earth's surface and about 42 per cent (four million sq. km) of Canada's land area.
"There is no doubt that northern regions are warming and permafrost is melting as shown by numerous observations and modeling studies," said Dr. Altaf Arain, co-author of the study and associate professor in the School of Geography & Earth Sciences. "However, there is large uncertainty about the rate and magnitude of permafrost degradation."
Previous studies using the US National Center for Atmospheric Research, Community Climate Model (NCAR CCSM) suggested that global warming is rapidly melting permafrost in northern regions. According to these studies, only one million sq. km of the currently estimated 10.5 million sq. km of permafrost would remain by the end of this century. However, these studies did not take peat or soil organic layer into account in the CCSM land surface scheme, the Community Land Model v3, said Arain.
Arain and co-authors Dr. Ming-ko (Hok) Woo, professor emeritus at the School of Geography & Earth Sciences, and graduate student Shuhua Yi used the CLM3 with several modifications and historical climate records. Their results indicated that although permafrost degradation was predicted over the 2000 to 2100 period, areas with mineral-based soil and no vegetation were most affected.
Forest cover provided more protection than shrubs or bare ground, and thick layers of peat were such effective insulators that permafrost showed only minimal decline even by 2100. A layer of peat above the permafrost acts as insulation by trapping air pockets, which reduces heat transfer.
Thawing permafrost can cause serious problems. Buildings, roads and pipelines built on permafrost may become unstable when it melts. In addition, thawing permafrost may contribute to global warming by releasing greenhouse gases.
"A lot of carbon is stored in northern regions as frozen soil organic matter," said Arain. "Release of this carbon to the atmosphere through decomposition may further accelerate global warming. Extensive land management, including the preservation of forested and peat-rich areas, may be the key to maintaining permafrost into the future."
The study, entitled Impacts of peat and vegetation on permafrost degradation under climate warming, was published in Geophysical Research Letters in August and also appeared in Nature Geosciences this month.