| |
| ||||||||||||||||||||||||||||
Proactive disclosure Print version   | |  Permafrost National Permafrost Databases
Knowledge of baseline permafrost thermal conditions is critical to monitoring and assessing changes in permafrost. This is important not only for climate change science, impact and adaptation studies but also critical for land use planning and infrastructure design, construction, operation and maintenance. To this end, the Geological Survey of Canada (GSC) has compiled national databases of permafrost thickness and ground temperature. The data are compiled from observations of over 500 government, university and industry boreholes. Information on site characteristics such as air temperature, snow cover and vegetation which influence the ground thermal regime and the permafrost distribution has also been compiled. The reference for each site is also provided and may be consulted for further information. Selected fields from the database may be viewed here. The entire database and complete text are published in the following GSC open file reports: For further information on each of these databases:
Other databases:
For further information on permafrost:
Publicly available data from published and unpublished sources have been compiled to produce a summary ground temperature database for northern Canada. The majority of the sites in this database are inactive, i.e. there is no ongoing monitoring of ground temperature. Investigations at the sites were undertaken for resource exploration, geotechnical investigations, and scientific research purposes. This database builds upon an unpublished ground temperature database for northern Canada originally developed at the Geological Survey of Canada in the mid 1980s by Young and Judge (1985). Selected attributes from the database available for viewing here, are listed below (note: data for each attribute is not available for all sites):
(click on field to get description) References Taylor, A.E. and Judge, A.S., 1974. Canadian Geothermal Data Collection - Northern Wells 1955 to February 1974; Geothermal Series #1, Geothermal Service Canada, Earth Physics Branch, E.M.R. Young, S. and Judge, A.S., 1985. A ground temperature data collection for Northern Canada; McGill University Workshop on Climate and thermal Regimes in Northern Canada. Unpublished Report. Description of fields The location of the measurement site was generally given by the source of information or a general broad regional name was assigned to the entry. For locations which have measurements for more than one site, each site name as given in the original source has been included. Latitude (°N) and longitude (°W) were either given by the source or approximated from the given site description. The elevation (if available) of each site is given in metres above sea level. Offshore sites are indicated by a negative value.
Sites that have been abandoned are classified as inactive (I) and data are no longer being collected. At the present time, to the best of our knowledge, data are still being collected at sites classified as active (A).
Boreholes have been classified as: The period over which ground temperature measurements were made is given when available. Dates are given as dd/mm/yy. Summary Ground Temperature Information
This includes mean annual near-surface ground temperature data. For deep boreholes, the ground surface temperature (i.e. depth = 0) is estimated by extrapolation of the ground temperature profile from depths below the level of zero amplitude. If a value is shown with "<=", the temperatures may not have returned to equilibrium following the disturbance due to drilling (see explanation under Detailed Ground Temperature Information). For shallow boreholes, the temperature given was determined directly from observations in upper few metres of the ground. Detailed Ground Temperature Information Mean, maximum and minimum annual ground temperature may be available at several depths for many of the sites included in the database. In the case of deep boreholes, the drilling process disturbs the thermal equilibrium. The time required for stabilization of temperatures ranges from several months to several years to decades. Equilibrium temperatures have been calculated for boreholes at which several temperature measurements were made over time after completion of drilling using the technique described by Taylor and Judge (1974). Data from the most recent temperature log are given for sites lacking the information required to calculate the equilibrium temperatures. At permafrost sites, the thickness (cm) of the seasonally thawed layer is given where available. Additional information about the site or data set may be given. In the case of deep boreholes for example, this may include information on drilling duration or whether equilibrium temperature has been calculated. A complete reference list for each record in the database is provided.
Publicly available information from published and unpublished sources has been compiled to produce a database of permafrost thickness, distribution and related conditions for northern Canada. The majority of sites in this database are inactive, i.e. there is no ongoing monitoring of permafrost conditions. Investigations at the sites were undertaken for resource exploration, geotechnical investigations, and scientific research purposes. The database builds upon an unpublished permafrost database for the Canadian permafrost region that was originally developed at the Geological Survey of Canada in the mid 1980s by Young and Judge (1986) and complements the summary ground temperature database for northern Canada (Smith and Burgess, 2000). Selected attributes from the database available for viewing here, are listed below (note: data for each attribute is not available for all sites):
[click on field to get description] [View National Map] [View Mackenzie Valley Map] [View Mackenzie Delta Map] [View Arctic Islands Map] References Smith, S. and Burgess, M.M., 2000. Ground temperature database for northern Canada; Geological Survey of Canada Open File Report #3954, 57 p. Young, S and Judge, A.S., 1986. Canadian permafrost distribution and thickness data collection: a discussion; Proceedings of National Student Conference on Northern Studies, W.P Adams and P.G. Johnson eds., p. 223-228. Description of fields The location of the measurement site was generally given by the source of information or a general broad regional name was assigned to the entry. For locations which have measurements for more than one site, each site name as given in the original source has been included. Latitude (°N) and longitude (°W) were either given by the source or approximated from the given site description. The elevation (if available) of each site is given in metres above sea level. Offshore sites are indicated by a negative value. Base Ice Bearing Permafrost (m)
The depth to the base of ice-bearing permafrost (IBPF) is given where available for deep hydrocarbon exploration sites. This is determined from geophysical logging (eg. electrical resistivity, sonic logs) conducted in the exploratory wells. In several cases the value may be preceded by a "<" and this indicates that the actual value is no more than the listed value. This might be the case if the base of IBPF was above the top of the logging interval. A ">" indicates that the depth to the base IBPF is probably greater than the value listed (eg. the borehole did not extend to the base. If no permafrost was present at the site "nopf" is entered. Most well logs exhibit a transition zone (Trans) below the base of ice-bearing permafrost and at temperatures just below 0°C within which ice and unfrozen water coexist, with the unfrozen water content increasing with depth. Within this zone, resistivity and sonic travel times gradually change due to the changing proportions of ice and unfrozen water. Depth of Zero Degree Isotherm (m)
This refers to depth to the base of permafrost which is defined as soil or rock that remains below 0°C regardless of whether or not it contains ice. This is generally determined through precise temperature measurements. A number of symbols may accompany the values in this field. A "U" in front of the value indicates that the value is unreliable. If a "U" appears by itself it indicates that permafrost is believed to be present at that site but there is no reliable value for its thickness. A ">" indicates that the estimated permafrost thickness is probably greater than the value listed (eg. temperature measurements may not have been made deep enough to get an accurate value). A "+" following the value indicates that the value is based on temperatures that may not have been in equilibrium (an interpolation of the latest temperature log) and the value is probably an underestimation. If no permafrost was present at the site "nopf" is entered. At sites where permafrost is present, the maximum thickness (cm) of the seasonally thawed layer (the active layer) is given where available. Additional information about the site or data set may be given. A complete reference list for each record in the database is provided.
|
