active-layer thickness
Link: http://w3id.org/permafrost/v/ipaglossary/t0006
Within: IPA Permafrost Glossary
Definition: The thickness of the layer of the ground that is subject to annual thawing and freeing in areas underlain by permafrost.
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active-layer thickness
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| Comment |
The thickness of the active layer depends on such factors as the ambient air temperature, vegetation, drainage, soil or rock type and total water content, snowcover, and degree and orientation of slope. As a rule, the active layer is thin in the High Arctic (it can be less than 15 cm) and becomes thicker farther south (1 m or more). The thickness of the active layer can vary from year to year, primarily due to variations in the mean annual air temperature, distribution of soil moisture, and snowcover. The thickness of the active layer includes the uppermost part of the permafrost wherever either the salinity or clay content of the permafrost allows it to thaw and refreeze annually, even though the material remains cryotic (T < 0°C). Use of the term "depth to permafrost" as a synonym for the thickness of the active layer is misleading, especially in areas where the active layer is separated from the permafrost by a residual thaw layer, that is, by a thawed or noncryotic (T> 0°C) layer of ground.
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| dcterms:source |
https://doi.org/10.4224/20386561
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