SNOW, GROUND ICE AND PERMAFROST
Indicators
- Snow water equivalencies
- Active layer depth
- Ground temperature
- Snow cover duration
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Current Knowledge
Snow provides water for spring runoff. It also serves as insulation that moderates the penetration of cold into the ground during winter. In the NWT, snow information is collected at about 90 sites. A few sites have been monitored for 50 years, but most have only been measured for a short period. As a result, it is difficult to identify trends over time. Amounts of snow are measured by translating the depth and weight of snow from a sample into the amount of water that a sample would produce if it were melted. Scientists call this "snow water equivalency."
Permafrost is ground that remains frozen for at least 2 years. This frozen ground may contain ice. The amount of ground ice in any particular location can vary significantly from almost none, to solid masses several metres thick. Most ground stability problems occur where ice-rich ground has been disturbed. The thickness of permafrost varies across the NWT, from over 100 m thick in the tundra near Inuvik to several metres thick near Fort Simpson. Permafrost is patchy and rare in parts of southern NWT and along the proposed pipeline corridor.
The ground above permafrost which thaws every summer, is called the active layer. Changes in the depth of the active layer can provide an indication of climate warming or cooling trends. During the last 100 years, in the northern parts of the prairie provinces and southernmost NWT, the southern edge of permafrost has moved about 100 km towards the north, due probably to a combination of land use practices and climate change.
Current Monitoring
- NWT snow survey network - INAC
- Snow accumulation/runoff in high latitude permafrost basins - National Hydrology Research Institute
- Snow measurements at weather stations - Environment Canada
- Snow water equivalent modeling - Environment Canada
- Mackenzie Valley and Delta shallow ground temperature and active layer monitoring network - Geological Survey of Canada
- Mackenzie Delta region deep ground temperature monitoring - INAC
- Permafrost conditions across treeline in western Arctic Canada - INAC, Carelton University
- Norman Wells pipeline corridor permafrost and terrain monitoring network and pipe-soil interaction studies - Natural Resources Canada
- Investigation of the permafrost as a drilling waste containment medium -INAC
- Long-term investigations of permafrost growth – Carleton University
- Soil temperature monitoring along Norman Wells pipeline - Enbridge/IPL
- Geomorphological investigations in the alpine tundra of western Mackenzie Mountains - University of Alberta
- Deformation of ice-rich permafrost slopes as a result of creep - Geological Survey of Canada
- Soil climate study – Agriculture Canada
- Predicted permafrost distribution modeling for the NWT - Geological Survey of Canada
- Tibbitt Lake post-fire study – INAC
- Interdisciplinary Studies Across Treeline (ISAT) -INAC
Gaps and Recommendations
There is a sparse snow survey network and little information on snow is collected in the Mackenzie Mountains and other key development areas. New monitoring sites in these areas should be established and monitored more frequently than once per year.
A full understanding of the potential impact of pipeline construction on permafrost and snow is needed. Other areas where information gaps could be addressed are: slope stability, active layer data, changes in albedo (the fraction of light that is reflected by a body of snow or ice), and the hydrological cycle. There is no current information about ground ice mapping, the release of nutrients from thawing snow, and requirements for industrial waste disposal in permafrost. Linkages need to be better understood between various indicators in order to assess cumulative effects of development on the environment.
Closer coordination between agencies could result in the closure of many gaps in monitoring for snow, ground ice and permafrost. Creating new monitoring programs in areas where development is anticipated would be helpful – for instance, gathering information about the pipeline right-of-way. There is also a need to assess: the role of forest fire; sump failure; and the movement of contaminants through permafrost. Keeping long-term snow, ice and permafrost records is an important step.
Source: A Preliminary State of Knowledge of Valued Components for the NWT Cumulative Impact Monitoring Program (NWT CIMP) and Audit - Final Draft. February 2002; updated February 2005 and June 2007.
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