Permafrost 101

Permafrost is ground that remains frozen for longer than two consecutive years, and it may or may not contain significant amounts of ice. In southern Yukon less than 25% of the land area is underlain by permafrost. In central Yukon, the distribution of permafrost is more extensive but still discontinuous, while north of Dawson, it is nearly continuous. Permafrost is generally thicker and colder as you move further north. It may be over 300 m thick and colder than -3° C in parts of the north slope, while in sporadic locations around Whitehorse it is only a few metres thick and is barely below 0° C. Permafrost distribution and ice content are influenced by a variety of local factors including topographic position, slope, aspect, vegetation cover, snow cover, and soil moisture and texture.

      

Yukon Permafrost distribution zones

Ice-rich permafrost becomes a hazard when it thaws which can cause landslides or ground subsidence (thermokarst). Permafrost thaw can be rapidly initiated by natural (fire or river erosion) and human disturbances that alter surface cover or groundwater flow. The presence and character (temperature and ice-content) of permafrost therefore heavily impact the cost, design, routing and construction techniques for infrastructure and pipelines. In southern Yukon’s warm, discontinuous permafrost terrain, frequent transitions between frozen and unfrozen terrain make infrastructure and pipeline engineering extremely challenging. Frost heave, thaw settlement, slope stability, and uncertainty in the rate of response of permafrost to anticipated climate change and forest fires are major geotechnical concerns.

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Ice-rich permafrost (white), northern Dawson Ranges

Despite the widespread presence of permafrost in Yukon, a major gap exists in the level of baseline data describing Yukon’s permafrost terrain. Detailed maps of permafrost character, distribution and ground temperature do not exist at a scale adequate for effectively assessing terrain stability hazards for infrastructure and communities, assessing the impacts of climate change and environmental disturbance on permafrost environments, or for facilitating responsible planning of infrastructure, transportation and development of hydrocarbon resources. For these reasons, YGS is involved with a number of projects aimed at better characterizing permafrost throughout the territory as well as improving dissemination of permafrost data.

 

                    FUN Tunnel Man Permafrost Educational Videos!

Source: University of Alaska Fairbanks Permafrost Outreach

  Episode 1    Episode 2    Episode 3    Episode 4      Episode 5 NEW!!

Permafrost Lectures from Adapting to a Warmer Earth: A Climate Change Lecture Series, Sept. - Oct, 2012

Below are some great links where you can learn more about permafrost