Disturbance by heat sources

 

Taliks

Disturbances are elements in the landscape (either natural or anthropogenic) which interact with the permafrost layer leading to local anomalies in thermal, hydrological, hydrogeological, or hydrochemical conditions. Hence, such disturbances can lead to the formation of taliks. A talik is defined as a layer or body of unfrozen ground existing continuously for more than a year in permafrost regions. The temperature of a talik ranges from above 0°C (noncryotic taliks) to below 0°C (cryotic taliks).

Different types of disturbances cause different types of taliks.

 

Disturbances lake

Lake:

Water has the ability to store and vertically transfer heat energy. The type and extent of the taliks (also referred to as "lake taliks") is related to the depth and water volume of the overlying water body. Larger water bodies can store and transfer more energy downward (see figure). Under lakes, both closed and open taliks can be formed.

Below large lakes, usually open taliks form, connection suprapermafrost and subpermafrost water.

Below small lakes, closed taliks which over time change into transient taliks may form. These are taliks which are gradually being eliminated by freezing. Expansion of thaw lake surface area in continuous permafrost zones will result in more talik development.

 

Disturbances river

River: 

Just as lakes, rivers can lead to the formation of both closed and open taliks, depending on the the characteristics of the river. Large rivers often promote the formation of open taliks.

 

Disturbances pipeline

Anthropogenic:

Elements/changes in landscape caused by human activity, i.e.

  • artificial water reservoirs
  • pipelines
  • spoil heaps
  • fills of coal- and sulfide containing rocks
  • artificial vegetation removal
  • infrastructures such as buildings and roads.

Artificial taliks can be easily formed in a discontinuous permafrost zone because a small, often rather short-term, change in hear exchange condition on the ground surface is sufficient for taliks to be formed.

 

Disturbances glacier

Other:

Other factors which promote talik formation, i. e.:

  • South-facing slopes or other areas in which the ground surface receives higher solar radiation than the surrounding area
  • Flood plains
  • Sites of concentrated discharge of groundwater or other areas where freezing is prevented due to flowing groundwater
  • Cold mountain glaciers due to glacial meltwater
  • Wildland fires
  • Volcanic craters, calderas, and other sites where thermal anomalies result from processes in the Earth's interior.

 

References:

http://www.physicalgeography.net/fundamentals/10ag.html

http://www.springerreference.com/docs/html/chapterdbid/330973.html

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