Cryosphere glossary
foehn
a warm wind blowing down an incline; a kind of katabatic wind.
fog
a hydrometeor consisting of a visible aggregate of minute water droplets (or ice crystals), suspended in the atmosphere near the earth's surface; according to international definition, fog reduces visibility below one kilometer, fog differs from cloud only in that the base of fog is at the earth's surface while clouds are above the surface; when composed of ice crystals, it is termed ice fog.
foliation
layering in glacier ice that has distinctive crystal sizes and/or bubbles; foliation is usually caused by stress and deformation that a glacier experiences as it flows over complex terrain, but can also originate as a sedimentary feature.
forbes bands
alternate bands of light and dark on a glacier; usually found below steep narrow icefalls and thought to be the result of different flow and ablation rates between summer and winter.
forel stripes
shallow, parallel grooves on the face of a large melting ice crystal.
foundation pile
structure used when the soil near the ground surface is not strong and the weight of the building must be carried by deeper soil layers.
fragmic cryogenic fabric
a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete units that are densely packed.
fragmoidal cryogenic fabric
a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which soil particles form discrete units that are coalescing.
Fram Strait
a sea channel connecting the Arctic Ocean and the Nordic Seas, running between Greenland and Spitsbergen. Fram Strait is the passageway where most drifting sea ice exits the Arctic.
frazil
small needle-like ice crystals, typically 3 to 4 millimeters in diameter, suspended in water, that represent the first stages of sea ice growth; they merge under calm conditions to form thin sheets of ice on the surface, frazil crystals consist of nearly pure fresh water.
Image
Frazil crystals.
Don Perovich, U.S. Army Cold Regions Research and Engineering Laboratory
frazil ice
fine spicules or plates of ice in suspension in water.
Image
Frazil crystals.
Don Perovich, U.S. Army Cold Regions Research and Engineering Laboratory
free water
free water is that portion of the pore water that is free to move between interconnected pores under the influence of gravity.
Image
Free water at the base of Dirt Glacier, British Columbia, in 1904.
C.W. Wright, archived at the World Data Center for Glaciology, Boulder, CO
freeboard
the thickness of sea ice protruding above the water level. Freeboard and draft comprise total sea ice thickness.
Image
Freeboard and draft comprise sea ice thickness.
Walt Meier
freeze-thaw cycle
freezing of a material followed by thawing.
freezeback
refreezing of thawed materials.
freezing (of ground)
the changing of phase from water to ice in soil or rock.
freezing degree-days
a measure of how cold it has been and how long it has been cold; the cumulative fdd is usually calculated as a sum of average daily degrees below freezing for a specified time period (10 days, month, season, etc.).
freezing drizzle
drizzle, the drops of which freeze on impact with the ground or with objects on the earth's surface or with aircraft in flight.
freezing front
the advancing boundary between frozen (or partially frozen) ground and unfrozen ground.
freezing index
the cumulative number of degree-days below 0 degrees Celsius for a given time period.