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The Cryosphere An interactive open-access journal of the European Geosciences Union
The Cryosphere, 11, 1-16, 2017
https://doi.org/10.5194/tc-11-1-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
02 Jan 2017
Strong degradation of palsas and peat plateaus in northern Norway during the last 60 years
Amund F. Borge, Sebastian Westermann, Ingvild Solheim, and Bernd Etzelmüller Department of Geosciences, University of Oslo, P.O. Box 1047, 0316 Oslo, Norway
Abstract. Palsas and peat plateaus are permafrost landforms occurring in subarctic mires which constitute sensitive ecosystems with strong significance for vegetation, wildlife, hydrology and carbon cycle. Firstly, we have systematically mapped the occurrence of palsas and peat plateaus in the northernmost county of Norway (Finnmark, ∼ 50 000 km2) by manual interpretation of aerial images from 2005 to 2014 at a spatial resolution of 250 m. At this resolution, mires and wetlands with palsas or peat plateaus occur in about 850 km2 of Finnmark, with the actual palsas and peat plateaus underlain by permafrost covering a surface area of approximately 110 km2. Secondly, we have quantified the lateral changes of the extent of palsas and peat plateaus for four study areas located along a NW–SE transect through Finnmark by utilizing repeat aerial imagery from the 1950s to the 2010s. The results of the lateral changes reveal a total decrease of 33–71 % in the areal extent of palsas and peat plateaus during the study period, with the largest lateral change rates observed in the last decade. However, the results indicate that degradation of palsas and peat plateaus in northern Norway has been a consistent process during the second half of the 20th century and possibly even earlier. Significant rates of areal change are observed in all investigated time periods since the 1950s, and thermokarst landforms observed on aerial images from the 1950s suggest that lateral degradation was already an ongoing process at this time. The results of this study show that lateral erosion of palsas and peat plateaus is an important pathway for permafrost degradation in the sporadic permafrost zone in northern Scandinavia. While the environmental factors governing the rate of erosion are not yet fully understood, we note a moderate increase in air temperature, precipitation and snow depth during the last few decades in the region.

Citation: Borge, A. F., Westermann, S., Solheim, I., and Etzelmüller, B.: Strong degradation of palsas and peat plateaus in northern Norway during the last 60 years, The Cryosphere, 11, 1-16, https://doi.org/10.5194/tc-11-1-2017, 2017.
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Palsas and peat plateaus are permafrost landforms in subarctic mires which constitute sensitive ecosystems with strong significance for vegetation, wildlife, hydrology and carbon cycle. We have systematically mapped the occurrence of palsas and peat plateaus in northern Norway by interpretation of aerial images from the 1950s until today. The results show that about half of the area of palsas and peat plateaus has disappeared due to lateral erosion and melting of ground ice in the last 50 years.
Palsas and peat plateaus are permafrost landforms in subarctic mires which constitute sensitive...
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