A major field program was undertaken in February and March 2007 by the Geological Survey of Canada in order to address gaps in baseline environmental information in the Mackenzie Valley, south of Norman Wells, Northwest Territories. Sites were selected to represent a range of ground-thermal, terrain, and vegetation conditions. Drilling of boreholes to depths of 20 m yielded data for characterization of subsurface materials at 16 locations, including physical properties of soil and ground-ice conditions. Twenty boreholes were preserved and instrumented with temperature cables and the data acquired has enabled a preliminary characterization of the ground-thermal regime. Key baseline information was generated for a suite of representative terrain types that may be utilized in planning northern development and environmental impact assessment. Ongoing data collection from thermal monitoring sites will facilitate improved characterization of current permafrost conditions and change detection.
ABSTRACT Research in geocryology is currently principally concerned with the effects of climate change on permafrost terrain. The motivations for most of the research are (1) quantification of the anticipated net emissions of CO 2 and CH 4 from warming and thaw of near‐surface permafrost and (2) mitigation of effects on infrastructure of such warming and thaw. Some of the effects, such as increases in ground temperature or active‐layer thickness, have been observed for several decades. Landforms that are sensitive to creep deformation are moving more quickly as a result, and Rock Glacier Velocity is now part of the Essential Climate Variable Permafrost of the Global Climate Observing System. Other effects, for example, the occurrence of physical disturbances associated with thawing permafrost, particularly the development of thaw slumps, have noticeably increased since 2010. Still, others, such as erosion of sedimentary permafrost coasts, have accelerated. Geochemical effects in groundwater from trace elements, including contaminants, and those that issue from the release of sediment particles during mass wasting have become evident since 2020. Net release of CO 2 and CH 4 from thawing permafrost is anticipated within two decades and, worldwide, may reach emissions that are equivalent to a large industrial economy. The most immediate local concerns are for waste disposal pits that were constructed on the premise that permafrost would be an effective and permanent containment medium. This assumption is no longer valid at many contaminated sites. The role of ground ice in conditioning responses to changes in the thermal or hydrological regimes of permafrost has re‐emphasized the importance of regional conditions, particularly landscape history, when applying research results to practical problems.
The temperature in the ground changes according to daily or longer temperature cycles in the air. The amount of ground temperature change also diminishes rapidly with depth. Temperatures to a depth of 20 m, the approximate depth to which the yearly temperature cycle penetrates, are presented for various environments in the Mackenzie valley. As a rough guideline, average ground temperatures are about 4°C warmer than mean annual air temperatures. This difference depends mainly on the insulating affect of vegetation and snow and changes in the moisture content of the active layer. Smaller differences may result in peatlands where summer drying of organic soils enhances their insulating capacity. Even without a change in climate, disturbance at the ground surface will alter the ground thermal regime. Examples from the Norman Wells to Zama, Alberta oil pipeline show warming and ground subsidence associated with the clearing of the pipeline right-of-way.
Permafrost has received much attention recently because surface temperatures are rising in most permafrost areas of the Earth, bringing permafrost to the edge of widespread thawing and degradation. The thawing of permafrost that already occurs at the southern limits of the permafrost zone can generate dramatic changes in ecosystems and in infrastructure performance. In this article, we describe an emerging system for comprehensive monitoring of permafrost temperatures, a system which is needed for timely detection of worldwide changes in permafrost stability, and for predictions of negative consequences of permafrost degradation. Permafrost is rock, sediment, or any other Earth material with a temperature that remains below 0°C for two or more years. Permafrost zones occupy up to 24% of the exposed land area of the Northern Hemisphere (Figure 1) [ Zhang et al. , 2000]. Permafrost ranges from very cold (temperatures of −10°C and lower) and very thick (more than 500 m and as much as 1400 m) in the Arctic, to warm (within 1 or 2° of the melting point) and thin (several meters or less in thickness) in the sub‐Arctic.
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