rduerr
commented
5 years ago The longer combined definition from the GCW glossaries will be something like:
The layer of ground that is subject to annual thawing and freezing in areas underlain by permafrost; also known as seasonal frost. In the zone of continuous permafrost the active layer generally reaches the permafrost table; in the zone of discontinuous permafrost it often does not. 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 < 0C). Its bottom surface is the frost table, beneath which may lie permafrost or talik. The depth of the active layer varies anywhere from a few inches to several feet. (Also called frost zone, mollisol.) The active layer depth may vary considerably from one year to another depending on a number of variables (cf. active layer thickness). If the ground thermal regime is no longer in long-term climatic equilibrium, active layers tend to show trends of increasing thickness.
The key bits of this definition are:
- Its a layer of ground
- Its in areas underlain by either continuous or discontinuous permafrost
- Its bottom surface is called the frost table
- It generally extends down to the permafrost table in the continuous permafrost zone
- It may include the uppermost part of the permafrost if salinity or clay content allow thawing and refreezing at temperatures below 0C
- In the discontinuous permafrost zone it may be underlain by talik and often does not extend down to the permafrost table
- It can be a few inches to several feet thick
- It's thickness changes if the ground is not in long-term climatic equilibrium
Synonyms: seasonal frost, frost zone, mollisol
Another term for ECSO.
definition: The layer of ground that is subject to annual thawing and freezing in areas underlain by permafrost.
source: https://nsidc.org/cryosphere/glossary/term/active-layer
This term looks tricky, but I'll assign this to myself for now.