Cryosphere Glossary

ablation

processes (melting, evaporation, sublimation) by which snow and ice are added to a glacier.

accumulation

processes by which snow and ice are added to a glacier.

albedo

a measure of the reflectivity of a surface ranging from 0 to 1; albedo is calculated by taking the ratio of reflected radiation to incoming radiation, such that a surface that reflects 100% of light hitting it has an albedo of 1, and a surface that absorbs 100% of the light hitting it has an albedo of 0.

anomaly

irregularity or deviation from normal.

anthropogenic

of, relating to, or resulting from the influence of human beings on nature.

balancing feedback loop

feedback in which an action produces a result that slows down and/or dampens an effect, tending to push a system towards stability.

brine

water with a high salt content.

causal connection

the relationship of cause and effect.

Coriolis effect

deflection caused by Earth's rotation.

crevasse

deep crack in an ice sheet or glacier.

cryosphere

the set of all locations on or beneath Earth's surface where frozen water exists.

dynamic

relating to energy and physical forces or to objects in motion.

eccentricity (e)

measure from 0 to 1 of how much an ellipse deviates from a perfect circle (how flattened the circle is; an orbit with an eccentricity of 0 is perfectly circular, and an orbit with an eccentricity of 1.0 is a parabola (no longer a closed orbit).

equilibrium

definition (in context of glacial mass balance).

fast ice

ice that is anchored to the shore or ocean bottom, typically over shallow ocean shelves at continental margins; fast ice is defined by the fact that it does not move with the winds or currents.

feedback

exchange between the input and the output of a system.

first-year ice

floating ice of no more than one year's growth developing from young ice; thickness ranges from 0.3 to 2 meters (1 to 6.6 feet); first-year ice is characteristically level (flat) where it is undisturbed by pressure, but can be rough and angular where ridges occur.

glacial

period within a glacial age, characterized by cooler temperatures and advancing glaciers. also called glaciation.

glacial age

any geological period in which long-term cooling takes place and ice sheets and glaciers exist.

glaciation

period within a glacial age, characterized by cooler temperatures and advancing glaciers. also called a glacial.

glacier

a mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer; many believe that a glacier must show some type of movement; others believe that a glacier can show evidence of past or present movement.

greenhouse gas

any gas, including carbon dioxide, water vapor, ozone and methane, that traps heat in the Earth's atmosphere.

hydropower

power derived from the force or energy of moving water.

iceberg

a piece of ice that has broken off from the end of a glacier that ends in water.

ice core

a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica, Greenland or from high mountain glaciers elsewhere.

ice sheet

a dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers (12 million acres) (e.g., the Greenland and Antarctic ice sheets).

ice shelf

portion of an ice sheet that spreads out over water.

interglacial

warm period within a glacial age.

internal ice stress

measurement of the compactness, or strength, of ice.

isotope

each of two or more forms of the same element that have equal numbers of protons but different numbers of neutrons in their nuclei, and therefore have different atomic masses but not chemical properties.

land ice

any part of Earth's ice cover that formed over land primarily from freezing precipitation, as opposed to sea ice formed by the freezing of seawater

mass balance

the difference between accumulation and ablation in a glacier; if accumulation is greater than ablation, mass balance is positive; if accumulation is less than ablation, mass balance is negative; if accumulation = ablation, mass balance is zero (equilibrium).

Milankovitch cycles

cyclical variations in the Earth's axial tilt, eccentricity, and precession thought to be responsible for the episodic nature of Earth's glacial and interglacial periods within the present Ice Age (the last couple of million years).

multiyear ice

ice that has survived at least one melt season; it is typically 2 to 4 meters (6.6 to 13.1 feet) thick and thickens as more ice grows on its underside.

new ice

a general category of ice representing the earliest stages of sea ice growth.

obliquity

tilt of Earth's rotational axis.

permafrost

layer of soil or rock, at some depth beneath the surface, in which the temperature has been continuously below 0°C for at least several years; it exists where summer heating fails to reach the base of the layer of frozen ground.

polar vortex

a large pocket of very cold air, typically the coldest air in the Northern Hemisphere, which sits over the polar region during the winter season.

precession

a change in the orientation of the rotational axis of a rotating body.

proxy data

data that paleoclimatologists gather from natural recorders of climate variability, e.g., tree rings, ice cores, fossil pollen, ocean sediments, coral and historical data, that can help extend our understanding of climate far beyond the 140 year instrumental record.

radiation budget

the relationship between how much energy the Earth gets from the Sun and how much energy the Earth-system radiates back into space.

reinforcing feedback loop

feedback in which an action produces a result that influences more of the same action, thus resulting in growth or decline.

salinity

measurement of salt content.

sea ice

any form of ice found at sea which formed from the freezing of sea water.

sea ice concentration

the fraction of an area that is covered by sea ice.

sea ice extent

the total area covered by some amount of ice, including open water between ice floes; sea ice extent is typically measured in square kilometers.

sea surface tilt

a force, determined by differences in sea surface level, that influences ice motion; several factors contribute to differences in the ocean surface level, including uneven heating, salinity variations, and currents, especially near coastal regions or ice shelves; this force is quite small compared to wind and current forces and is not important over periods of several days, but can have a noticeable effect on sea ice motion over longer periods of months or years.

thermodynamic equilibrium

the state of a system in which its energy distribution is such that all parts of the system have the same temperature and no heat flows.

thermodynamics

the study of conversions between heat and other forms of energy.

thermohaline circulation

deep-ocean currents driven by differences in the water's density, which is controlled by temperature (thermo) and salinity (haline).

young ice

a general category of ice that is less than one year old and about 10 to 30 centimeters (4 to 12 inches) thick.