Cryosphere glossary
disequilibrium permafrost
permafrost that is not in thermal equilibrium with the existing mean annual surface or sea-bottom temperature and the geothermal heat flux.
draft
the thickness of sea ice extending below the water level. Draft and freeboard comprise total sea ice thickness.
drain channel
preferred path for meltwater to flow from the surface through a snow cover.
drift glacier
a semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a catchment glacier or a snowdrift glacier.
drift ice
ice that moves from winds, currents, or other forces.
drift of ice
displacement of a sea ice field from its place of origin under the effect of ocean currents and winds.
drifting buoy
floating (or drifting on ice) ocean buoy equipped with meteorological and/or oceanographic sensing instruments linked to transmitting equipment for sending the observed data to collecting centers.
drifting snow
snow raised from the surface of the earth by the wind to a height of less than 1.5 to 2.0 meters (5 to 6.6 feet) above the surface; it dose not restrict horizontal visibility at 2 meters (6.6 feet) or more above the surface.
drifting stations
research stations on the floes of the arctic ocean.
drizzle
very small, uniformly distributed water drops that appear to float while following air currents; unlike fog droplets, drizzle falls to the ground.
drumlin
remnant elongated hills formed by historical glacial action; it is not clear exactly how they are formed and why they form only in some glaciated regions.
Image
Drumlin field. Manitoba, Canada.
drunken forest
trees leaning in random directions caused by melting permafrost.
dry density
the mass of a unit volume of dried material (e.g. soil).
dry frozen ground
frozen ground with a very low total water content consisting almost completely of interfacial water, and not cemented by ice.
dry permafrost
permafrost containing neither free water nor ice.
dump moraine
a mound or layer of moraine formed along the edge of a glacier by rock that falls off the ice; sometimes called a ground moraine.
dynamic modulus of elasticity
the ratio of stress to strain for a material under dynamic loading conditions.
dynamic Poisson's ratio
the absolute value of the ratio between the linear strain changes, perpendicular to and in the direction of a given uniaxial stress change, respectively, under dynamic loading conditions.
earth hummock
a hummock having a core of silty and clayey mineral soil which may show evidence of cryoturbation.
earth radiation
the total infrared radiation emitted from the earth's surface; to be carefully distinguished from effective terrestrial radiation, atmospheric radiation, and insolation.