Cryosphere glossary
tarn
a small mountain lake or pool.
telescoped ice
deformed sea ice in which one piece has overridden another; also called rafted ice.
temperature
a physical quantity characterizing the mean random motion of molecules in a physical body; in other words, it is a measure of the degree of hotness or coldness of a substance.
temperature profile
the graphic or analytical expression of the variation in ground temperature with depth.
temperature-gradient metamorphism
snow metamorphism that occurs when there are strong differences in temperature between the bottom and top of a snow layer.
terminus
the lowest end of a glacier, also called the glacier toe or glacier snout.
terrestrial radiation
longwave radiation emitted by the earth, including its atmosphere.
thaw basin
a depression of the permafrost table created by naturally induced thawing.
thaw bulb
a zone of thawed ground below or surrounding a man-made structure placed on or in permafrost and maintained at temperatures above 0 degrees Celsius.
thaw consolidation
time-dependent compression resulting from thawing of frozen ground and subsequent draining of excess water.
thaw consolidation ratio
a dimensionless ratio describing the relationship between the rate of thaw and the rate of consolidation of a thawing soil, which is considered to be a measure of the relative rates of generation and expulsion of excess water during thaw.
thaw hole
vertical hole in floating ice formed when a puddle melts through to the underlying water.
thaw penetration
the downward movement of the thawing front during thawing of frozen ground.
thaw settlement
compression of the ground due to thaw consolidation.
thaw sink
a closed thaw basin with subterranean drainage.
thaw slumping
a slope failure mechanism characterized by the melting of ground ice, and downslope sliding and flowing of the resulting debris.
thaw strain
the amount that frozen ground compresses upon thawing.
thaw unconformity
a boundary sometimes identified in perennially frozen ground, representing the base of a relict active layer, as well as the corresponding earlier permafrost table.
thaw weakening
the reduction in shear strength due to the decrease in effective stresses resulting from the generation and slow dissipation of excess pore pressures when frozen soils containing ice are thawing.
thaw-sensitive permafrost
perennially frozen ground which, upon thawing, will experience significant thaw settlement and suffer loss of strength to a value significantly lower than that for similar material in an unfrozen condition.