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terrestrial radiation

longwave radiation emitted by the earth, including its atmosphere.

Topic: 
climatology and meteorology

thaw basin

a depression of the permafrost table created by naturally induced thawing.

Topic: 
frozen ground or permafrost

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.
Topic: 
frozen ground or permafrost

thaw consolidation

time-dependent compression resulting from thawing of frozen ground and subsequent draining of excess water.
Topic: 
frozen ground or permafrost

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.
Topic: 
frozen ground or permafrost

thaw hole

vertical hole in floating ice formed when a puddle melts through to the underlying water.
Topic: 
sea ice
freshwater ice

thaw penetration

the downward movement of the thawing front during thawing of frozen ground.
Topic: 
frozen ground or permafrost

thaw settlement

compression of the ground due to thaw consolidation.
Topic: 
frozen ground or permafrost

thaw sink

a closed thaw basin with subterranean drainage.
Topic: 
frozen ground or permafrost

thaw slumping

a slope failure mechanism characterized by the melting of ground ice, and downslope sliding and flowing of the resulting debris.
Topic: 
frozen ground or permafrost

thaw strain

the amount that frozen ground compresses upon thawing.
Topic: 
frozen ground or permafrost

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.
Topic: 
frozen ground or permafrost

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.
Topic: 
frozen ground or permafrost

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.
Topic: 
frozen ground or permafrost

thaw-stable permafrost

perennially frozen ground which, upon thawing, will not experience either significant thaw settlement or loss of strength.
Topic: 
frozen ground or permafrost

thawed ground

previously frozen ground in which all ice has melted.
Topic: 
frozen ground or permafrost

thawing (of frozen ground)

melting of the ice in frozen ground, usually as a result of a rise in temperature.
Topic: 
frozen ground or permafrost

thawing front

the advancing boundary between thawed ground and frozen ground.
Topic: 
frozen ground or permafrost

thawing index

the cumulative number of degree-days above 0 degrees Celsius for a given time period.
Topic: 
frozen ground or permafrost
climatology and meteorology

theodolite

an optical instrument used to visually track a radiosonde balloon and determine its bearing and elevation while in flight.
Topic: 
climatology and meteorology

thermal conductivity

the quantity of heat that will flow through a unit area of a substance in unit time under a unit temperature gradient.
Topic: 
frozen ground or permafrost

thermal diffusivity

the ratio of the thermal conductivity to the volumetric heat capacity.
Topic: 
frozen ground or permafrost

thermal erosion

the erosion of ice-bearing permafrost by the combined thermal and mechanical action of moving water.
Topic: 
frozen ground or permafrost

thermal expansion (or contraction) coefficient

the volume change per unit volume of a substance due to a one degree change in its temperature.
Topic: 
frozen ground or permafrost

thermal pile

a foundation pile on which natural convection or forced circulation cooling systems or devices have been installed to remove heat from the ground.
Topic: 
frozen ground or permafrost

thermal properties of frozen ground

the properties of the ground governing the flow of heat through it, and its freezing and thawing conditions.
Topic: 
frozen ground or permafrost

thermal regime of the ground

a general term encompassing the temperature distribution and heat flows in the ground and their time-dependence.
Topic: 
frozen ground or permafrost

thermal talik

a layer or body of unfrozen ground (in a permafrost area) in which the temperature is above 0 degrees Celsius due to the local thermal regime of the ground.
Topic: 
frozen ground or permafrost

thermal-contraction crack

a tensile fracture resulting from thermal stresses in frozen ground.
Topic: 
frozen ground or permafrost

thermal-contraction-crack ice

ice formed in thermal contraction cracks in the ground.
Topic: 
frozen ground or permafrost

thermo-erosional cirque

the usually steep, horseshoe-shaped headwall of a retrogressive thaw slump.
Topic: 
frozen ground or permafrost

thermo-erosional niche

a recess at the base of a river bank or coastal bluff, produced by thermal erosion of ice-bonded permafrost.
Topic: 
frozen ground or permafrost

thermodynamic equilibrium thickness

the thickness at which ice no longer grows because it is so thick that heat from the ocean can no longer be conducted through the ice; it may take several years of growth and melt for ice to reach an equilibrium thickness.
Topic: 
sea ice

thermodynamics

study of the links between heat and energy. First law of thermodynamics states that heat is energy and the amount of energy within a system cannot change.

thermograph

an instrument continuously recording temperature.

Topic: 
climatology and meteorology

thermokarst

the process by which characteristic landforms result from the thawing of ice-rich permafrost or the melting of massive ice.
Topic: 
frozen ground or permafrost

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