Cryosphere glossary
headwall
a steep cliff, usually the uppermost part of a cirque.
heat balance
equilibrium between the gain and loss of heat at a specific place or for a specific system.
heat balance of the earth-atmosphere system
the equilibrium that exists between the radiation received by the earth and atmosphere from the sun and that emitted by the earth and atmosphere.
heat budget
relation between fluxes of heat into and out of a given region or body and the heat stored by the system; in general, this budget includes advective, evaporative, and other terms as well as a radiation term.
heat capacity
the amount of heat required to raise the temperature of a unit mass of a substance by one degree.
heat flux
the amount of heat transferred across a surface of unit area in a unit time.
heat sink
process, or region, in which energy is removed from the atmosphere in the form of heat.
heat source
process, or region, in which energy is added to the atmosphere in the form of heat.
heaving pressure
upward pressure developed during freezing of the ground.
high
area of high pressure in the atmosphere; used interchangeably with anticyclone.
high-center polygon
an ice-wedge polygon in which melting of the surrounding ice wedges has left the central area in a relatively elevated position.
high-level clouds
typically thin, white clouds above 6,000 meters (20,000 feet); at these altitudes, temperatures are so cold that clouds are composed primarily of ice crystals; includes cirrus, cirrocumulus and cirrostratus clouds.
hoarfrost
a deposit of interlocking ice crystals (hoar crystals) formed by direct sublimation on objects, usually those of small diameter freely exposed to the air, such as tree branches, plant stems and leaf edges, wires, poles, etc.; the surfaces of these objects are sufficiently cooled, mostly by nocturnal radiation, to cause the direct sublimation of the water vapor contained in the ambient air.
horn
a peak or pinnacle thinned and eroded by three or more glacial cirques.
Image
The Matterhorn in Switzerland was carved away by glacial erosion.
World Data Center for Glaciology, Boulder, CO
hostile ice
from the point of view of the submariner, an ice canopy containing no large ice skylights or other features which permit a submarine to surface.
humidity
(1) water vapor content of the air. (2) some measure of the water-content of air; see also absolute humidity, relative humidity, specific humidity, dew point.
hummock
(1) [sea ice] a smooth hill of ice that forms on the sea ice surface from eroding ridges, particularly during the summer melt; the formation of hummocks is similar to young mountain peaks with steep slopes that erode into smooth, rolling hills. (2) [frozen ground] Small lumps of soil pushed up by frost action, often found in uniformly spaced in large groups. Hummocks can form in areas of permafrost or seasonally frozen ground, and are one of the most common surface features of the Arctic.
Image
Hummocks make the sea ice surface appear as rolling hills.
Ted Maksym, United States Naval Academy
hummocking
[sea ice] pressure process by which floating ice becomes broken up into hummocks.
hydration shattering
a form of weathering that affects all rocks; water freezes in pores and cracks, which leads to an increase in specific volume (vol/unit mass) of the water, producing stress that is greater than the tensile strength of all common rocks; ultimately leads to shattering and fracturing of the rocks.
hydraulic conductivity
the volume of fluid passing through a unit cross section in unit time under the action of a unit hydraulic potential gradient.