Permafrost thaw threatens mountains
New research shows in greater detail which parts of Scandinavian earth is permafrost
M. Michael Brady
Permafrost is permanently frozen ground found mostly at high latitudes in the Northern Hemisphere. It was first observed in 1577 by Sir Martin Frobisher on his second voyage in search of the Northwest Passage. But the word for it is relatively new, perhaps because permanently frozen ground attracted little attention for 300 years thereafter.
Then, in the late 19th century, Russian engineers became the first to cope with permanently frozen ground in building the Trans-Siberian railroad across frozen tundra. Later, around the turn of the century, Gold Rush miners and engineers encountered similar problems. Likewise, in 1942 the U.S. Army Corps of Engineers dealt with the complications of frozen ground in building the Alcan Highway from the contiguous U.S. through Canada to Alaska. One of the outcomes of that undertaking was linguistic. In 1943, the word “permafrost” came into the language when Siemon W. Muller of the U.S. Geological Survey proposed it as a contraction of the scientific term “permanently frozen ground” in a report released by the U.S. Army, Office of Chief of Engineers.
Today, 26 countries around the globe conduct scientific research on permafrost and have pooled their expertise in the International Permafrost Association and the Global Terrestrial Network for Permafrost (GTN-P). Many of the challenges have been recognized since the early days of building in permafrost zones. A variety of techniques have been developed to cope with them, such as building deep foundations or erecting buildings on piles to prevent foundation failure due to permafrost thaw caused by the heat of the building.
A more alarming challenge has recently arisen in the High North. Global warming may destabilize the mountains of Scandinavia as it progressively thaws the permafrost that binds them together. Unstable mountain slopes threaten roads, railroads, buildings, and lives. Moreover, thawing of the permafrost areas of the marshes of the High North may release enormous quantities of greenhouse gasses. The contribution from Scandinavian marshes is small compared to the contributions from the far larger marshes of Siberia, Alaska, and the Yukon. But it’s a substantiated threat, as clear signs of the degradation of Scandinavian marshes have been observed over the past 50 years. The challenge then is to understand how permafrost in mountainous areas will respond to future climate change.
That’s easier said than done. Permafrost isn’t readily apparent. It may start near a ground surface or deeper down. It’s formed and sustained by the low overall temperature of a land area but also depends on local variations in vegetation, soil properties, and wintertime snow cover. The wind-driven drifting of snow can lead to extreme variations in snow depth over short distances on the ground, depending on topography and on prevailing winter winds. So there’s no clear overview of where permafrost is located and consequently can be troublesome if it thaws.
Geoscientist Kjersti Gisnås of the Department of Avalanches and Rockslides of the Norwegian Geotechnical Institute saw that gap in the knowledge of permafrost as a problem worthy of attack. So she researched it and this past April presented her findings in a University of Oslo doctoral dissertation.
Her research had started with an assessment of the drawbacks of the customary methods of producing permafrost maps. Drilling holes in ground to measure subsurface temperatures is accurate but indicates permafrost conditions only at the points where the holes are drilled. Broader overviews are extracted from wintertime measurements of snow cover. Because snow actually is a good insulator, the deeper the snow cover, the warmer the underlying ground. But existing snow cover mapping techniques, as used in climate research and weather forecasting, produce low-resolution images that cannot define details smaller than about a kilometer (about six tenths of a mile). So for the purposes of charting permafrost, they miss much, such as the frequent variation in snow cover from deep in a valley to zero on a blown-bare ridge just above it.
The ensuing research was devoted to measurements in the field and to developing statistical methods to include small-scale variations of snow cover in regional weather and permafrost computational models. In turn, the new models were used to generate an improved, higher-resolution map of the distribution of permafrost in Scandinavia. As the new map shows, permafrost is most prevalent in the central mountains of southern Norway and in the mountain chains along the border between Norway and Sweden in the far north.
Permafrost modelling over different scales in arctic and high-mountain environments, by Kjersti Gisnås, University of Oslo, Department of Geosciences, January 2016, dissertation no. 1734, ISSN 1501-7710, link to research archive with Abstract at www.duo.uio.no/handle/10852/51037.
Permafrost by Louis L. Ray, U.S. Geological Survey public information monograph published 1993, modified August 2012, downloadable PDF at: pubs.er.usgs.gov/publication/70039262.
This article originally appeared in the Aug. 26, 2016, issue of The Norwegian American. To subscribe, visit SUBSCRIBE or call us at (206) 784-4617.