Cryosphere glossary
data analysis
Provides the user the ability to calculate or compare data parameters.
de-icing
the removal of ice accumulation on aircraft, ships and other objects by mechanical, thermal or chemical devices.
dead ice
any part of a glacier which has ceased to flow; dead ice is usually covered with moraine.
debris flow
a sudden and destructive variety of landslide, in which loose material on a slope, with more than 50% of particles larger than sand size, is mobilized by saturation and flows down a channel or canyon.
deformability
the ability of a material to change its shape or size under the influence of an external or internal agency, such as stress, temperature, or pore pressure.
degree of saturation
(1) the total degree of saturation of frozen soil is the ratio of the volume of ice and unfrozen water in the soil pores to the volume of the pores (2) the degree of saturation of frozen soil by ice is the ratio of the volume of ice in the soil pores to the volume of the pores.
degree-day (C or F)
a derived unit of measurement used to express the departure of the mean temperature for a day from a given reference (or base) temperature.
delayed strength
the failure strength of a material at a given strain rate or after a given period under deviatoric stress.
dendrite
hexagonal ice crystals with complex and often fernlike branches.
density of frozen ground
the mass of a unit volume of frozen soil or rock.
depression
in meteorology, an area of low pressure (i.e. a low); usually applies to a particular stage in the development of a cyclone.
depth hoar
a kind of hoarfrost; ice crystals that develop by sublimation within a layer of dry snow; characterized by rapid recrystallization, usually caused by large temperature gradients; similar in physical origin to crevasse hoar; crystals are faceted, rather than rounded.
depth of seasonal frost penetration
the maximum thickness of the seasonally frozen layer.
depth of snow
vertical interval between the top surface of a snow layer and the ground beneath; the layer is assumed to be evenly spread over the ground which it covers.
depth of thaw
the minimum distance between the ground surface and frozen ground at any time during the thawing season in an area subject to seasonal freezing and thawing.
depth of zero annual amplitude
the distance from the ground surface downward to the level beneath which there is practically no annual fluctuation in ground temperature.
desiccation crack
crack or fissure developed in fine-grained soil material as a result of shrinkage during drying.
desiccation polygon
closed, multi-sided, patterned ground feature formed by desiccation cracks in fine-grained soil material, usually less than 2 meters (6.6 feet) in diameter.
design depth of frost penetration
(1) (North American usage) the mean of the three largest depths of seasonal frost penetration measured during the past thirty years, or the largest depth of seasonal frost penetration beneath a snow-free soil surface measured during the past ten years (2) (Russian usage) the mean of the depths of seasonal frost penetration measured during at least the last ten years with the ground surface free of snow and the groundwater level below the depth of seasonal frost penetration.
design freezing index
the cumulative number of degree-days below 0 degrees Celsius, calculated by taking the average of the seasonal freezing indices for the three coldest winters in the most recent 30 years of record.