- Thaw depth
In
soil science , the thaw depth or thaw line is the level down to which thepermafrost soil will normallythaw eachsummer in a given area.The layer of soil over the thaw depth is calles the
active layer , while the soil below is called inactive layer.The term frost front refers to the varying position of the thaw line during the periods of freezing/thawing.
The knowledge of the thaw depth is important for the two major reasons: its influence on the
ecology and onconstruction (buildings , pipelines,road s, etc.). These influences are mediated by the effects of the dynamics biological, pedologic, geomorphologic, biogeochemical, and hydrologic processes in permafrost.In ecology,
root s ofplant s cannot penetrate beyond the active layer, which places restrictions on which plants can grow in permafrost.In construction, the thaw depth is a major factor in ensuring the structural integrity of the objects in question.
The primary factor that determines the thaw depth is the maximal air temperature. The
soil type is another important factor: coarser textures of theparent material have higherthermal conductivity , and, e.g., sandy soils have much deeper thaw line thanclay s. Yet another factors are thevegetation and the percentage of thesoil organic matter , which influence the bulk density of the soil, and hence thermal conductivity. [ Oelke, C., T. Zhang, M. Serreze, and R. Armstrong, 2003: Regional-scale modeling of soil freeze/thaw over the Arctic drainage basin. J. Geophys. Res., 108 (D10): Art.No. 4314 May 29 2003.]References
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