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Ice is
water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
frozen into a
solid Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ...
state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less
opaque Opacity or opaque may refer to: * Impediments to (especially, visible) light: ** Opacities, absorption coefficients ** Opacity (optics), property or degree of blocking the transmission of light * Metaphors derived from literal optics: ** In lingu ...
bluish-white color. In the
Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
, ice is abundant and occurs naturally from as close to the Sun as Mercury to as far away as the
Oort cloud The Oort cloud (), sometimes called the Öpik–Oort cloud, first described in 1950 by the Dutch astronomer Jan Oort, is a theoretical concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from ...
objects. Beyond the Solar System, it occurs as
interstellar ice Interstellar ice consists of grains of volatiles in the ice phase that form in the interstellar medium. Ice and dust grains form the primary material out of which the Solar System was formed. Grains of ice are found in the dense regions of molecular ...
. It is abundant on
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
's surfaceparticularly in the polar regions and above the snow lineand, as a common form of
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
and deposition, plays a key role in Earth's
water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, is a biogeochemical cycle that describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly cons ...
and
climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...
. It falls as snowflakes and hail or occurs as frost, icicles or ice spikes and aggregates from snow as glaciers and ice sheets. Ice exhibits at least eighteen phases ( packing geometries), depending on temperature and pressure. When water is cooled rapidly (
quenching In materials science, quenching is the rapid cooling of a workpiece in water, oil, polymer, air, or other fluids to obtain certain material properties. A type of heat treating, quenching prevents undesired low-temperature processes, such as pha ...
), up to three types of
amorphous ice Amorphous ice (non-crystalline or "vitreous" ice) is an amorphous solid form of water. Common ice is a crystalline material wherein the molecules are regularly arranged in a hexagonal lattice, whereas amorphous ice has a lack of long-range orde ...
can form depending on its history of pressure and temperature. When cooled slowly, correlated proton tunneling occurs below (, ) giving rise to
macroscopic quantum phenomena Macroscopic quantum phenomena are processes showing quantum behavior at the macroscopic scale, rather than at the atomic scale where quantum effects are prevalent. The best-known examples of macroscopic quantum phenomena are superfluidity and su ...
. Virtually all ice on Earth's surface and in its atmosphere is of a
hexagonal In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A '' regular hexagon'' has ...
crystalline structure In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns t ...
denoted as ice Ih (spoken as "ice one h") with minute traces of cubic ice, denoted as ice Ic and, more recently found,
Ice VII Ice VII is a cubic crystalline form of ice. It can be formed from liquid water above 3 GPa (30,000 atmospheres) by lowering its temperature to room temperature, or by decompressing heavy water (D2O) ice VI below 95 K. (Different types of ice, fr ...
inclusions in diamonds. The most common
phase transition In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states o ...
to ice Ih occurs when liquid water is cooled below (, ) at
standard atmospheric pressure The standard atmosphere (symbol: atm) is a unit of pressure defined as Pa. It is sometimes used as a ''reference pressure'' or ''standard pressure''. It is approximately equal to Earth's average atmospheric pressure at sea level. History The s ...
. It may also be deposited directly by
water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous p ...
, as happens in the formation of frost. The transition from ice to water is melting and from ice directly to water vapor is sublimation. Ice is used in a variety of ways, including for cooling, for
winter sport Winter sports or winter activities are competitive sports or non-competitive recreational activities which are played on snow or ice. Most are variations of skiing, ice skating and sledding. Traditionally, such games were only played in cold are ...
s, and
ice sculpting Ice sculpture is a form of sculpture that uses ice as the raw material. Sculptures from ice can be abstract or realistic and can be functional or purely decorative. Ice sculptures are generally associated with special or extravagant events becaus ...
.


Physical properties

As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered to be a
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
. It possesses a regular
crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...
structure based on the
molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...
of water, which consists of a single
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
atom
covalently A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...
bonded to two hydrogen atoms, or H–O–H. However, many of the physical properties of water and ice are controlled by the formation of hydrogen bonds between adjacent oxygen and hydrogen atoms; while it is a weak bond, it is nonetheless critical in controlling the structure of both water and ice. An unusual property of water is that its solid form—ice frozen at
atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...
—is approximately 8.3% less dense than its liquid form; this is equivalent to a volumetric expansion of 9%. The
density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
of ice is 0.9167–0.9168 g/cm3 at 0 °C and standard atmospheric pressure (101,325 Pa), whereas water has a density of 0.9998–0.999863 g/cm3 at the same temperature and pressure. Liquid water is densest, essentially 1.00 g/cm3, at 4 °C and begins to lose its density as the water molecules begin to form the
hexagonal In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A '' regular hexagon'' has ...
crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
s of
ice Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaqu ...
as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid. Density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm3 at −180 °C (93 K). When water freezes, it increases in volume (about 9% for fresh water). The effect of expansion during freezing can be dramatic, and ice expansion is a basic cause of
freeze-thaw Frost weathering is a collective term for several mechanical weathering processes induced by stresses created by the freezing of water into ice. The term serves as an umbrella term for a variety of processes such as frost shattering, frost wedg ...
weathering of rock in nature and damage to building foundations and roadways from
frost heaving Frost heaving (or a frost heave) is an upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated in ...
. It is also a common cause of the flooding of houses when water pipes burst due to the pressure of expanding water when it freezes. The result of this process is that ice (in its most common form) floats on liquid water, which is an important feature in Earth's
biosphere The biosphere (from Greek βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all ecosystems. It can also ...
. It has been argued that without this property, natural bodies of water would freeze, in some cases permanently, from the bottom up, resulting in a loss of bottom-dependent animal and plant life in fresh and sea water. Sufficiently thin
ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at La ...
s allow light to pass through while protecting the underside from short-term weather extremes such as wind chill. This creates a sheltered environment for bacterial and algal colonies. When sea water freezes, the ice is riddled with brine-filled channels which sustain sympagic organisms such as bacteria, algae, copepods and annelids, which in turn provide food for animals such as krill and specialised fish like the bald notothen, fed upon in turn by larger animals such as
emperor penguins The emperor penguin (''Aptenodytes forsteri'') is the tallest and heaviest of all living penguin species and is endemic to Antarctica. The male and female are similar in plumage and size, reaching in length and weighing from . Feathers of th ...
and
minke whales The minke whale (), or lesser rorqual, is a species complex of baleen whale. The two species of minke whale are the common (or northern) minke whale and the Antarctic (or southern) minke whale. The minke whale was first described by the Danish na ...
. When ice melts, it absorbs as much
energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...
as it would take to heat an equivalent mass of water by 80 °C. During the melting process, the temperature remains constant at 0 °C. While melting, any energy added breaks the hydrogen bonds between ice (water) molecules. Energy becomes available to increase the thermal energy (temperature) only after enough hydrogen bonds are broken that the ice can be considered liquid water. The amount of energy consumed in breaking hydrogen bonds in the transition from ice to water is known as the '' heat of fusion''. As with water, ice absorbs light at the red end of the spectrum preferentially as the result of an overtone of an oxygen–hydrogen (O–H) bond stretch. Compared with water, this absorption is shifted toward slightly lower energies. Thus, ice appears blue, with a slightly greener tint than liquid water. Since absorption is cumulative, the color effect intensifies with increasing thickness or if internal reflections cause the light to take a longer path through the ice. Other colors can appear in the presence of light absorbing impurities, where the impurity is dictating the color rather than the ice itself. For instance, icebergs containing impurities (e.g., sediments, algae, air bubbles) can appear brown, grey or green. Because ice in natural environments is usually close to its melting temperature, its hardness shows pronounced temperature variations. At its melting point, ice has a
Mohs hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by t ...
of 2 or less, but the hardness increases to about 4 at a temperature of and to 6 at a temperature of , the vaporization point of solid
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
(dry ice).


Phases

Ice may be any one of the 19 known solid crystalline phases of
water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
, or in an amorphous solid state at various densities. Most liquids under increased pressure freeze at ''higher'' temperatures because the pressure helps to hold the molecules together. However, the strong hydrogen bonds in water make it different: for some pressures higher than , water freezes at a temperature ''below'' 0 °C, as shown in the phase diagram below. The melting of ice under high pressures is thought to contribute to the movement of
glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as ...
s. Ice, water, and
water vapour (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...
can coexist at the
triple point In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.. It is that temperature and pressure at which the sub ...
, which is exactly at a pressure of 611.657  Pa. The
kelvin The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phy ...
was in fact defined as of the difference between this triple point and absolute zero, though this definition changed in May 2019. Unlike most other solids, ice is difficult to superheat. In an experiment, ice at −3 °C was superheated to about 17 °C for about 250 picoseconds. Subjected to higher pressures and varying temperatures, ice can form in 19 separate known crystalline phases. With care, at least 15 of these phases (one of the known exceptions being ice X) can be recovered at ambient pressure and low temperature in
metastable In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball i ...
form. The types are differentiated by their crystalline structure, proton ordering, and density. There are also two
metastable In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball i ...
phases of ice under pressure, both fully hydrogen-disordered; these are IV and XII. Ice XII was discovered in 1996. In 2006,
XIII XIII may refer to: * 13 (number) or XIII in Roman numerals * 13th century in Roman numerals * XIII (comics), ''XIII'' (comics), a Belgian comic book series by Jean Van Hamme and William Vance ** XIII (2003 video game), ''XIII'' (2003 video game), a ...
and XIV were discovered. Ices XI, XIII, and XIV are hydrogen-ordered forms of ices I, V, and XII respectively. In 2009, ice XV was found at extremely high pressures and −143 °C. At even higher pressures, ice is predicted to become a
metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
; this has been variously estimated to occur at 1.55 TPa or 5.62 TPa. As well as crystalline forms, solid water can exist in amorphous states as
amorphous ice Amorphous ice (non-crystalline or "vitreous" ice) is an amorphous solid form of water. Common ice is a crystalline material wherein the molecules are regularly arranged in a hexagonal lattice, whereas amorphous ice has a lack of long-range orde ...
(ASW) of varying densities. Water in the interstellar medium is dominated by amorphous ice, making it likely the most common form of water in the universe. Low-density ASW (LDA), also known as hyperquenched glassy water, may be responsible for
noctilucent clouds Noctilucent clouds, or night shining clouds, are tenuous cloud-like phenomena in the upper atmosphere of Earth. When viewed from space, they are called polar mesospheric clouds (PMCs), detectable as a diffuse scattering layer of water ice crysta ...
on Earth and is usually formed by deposition of water vapor in cold or vacuum conditions. High-density ASW (HDA) is formed by compression of ordinary ice I or LDA at GPa pressures. Very-high-density ASW (VHDA) is HDA slightly warmed to 160 K under 1–2 GPa pressures. In outer space, hexagonal crystalline ice (the predominant form found on Earth) is extremely rare. Amorphous ice is more common; however, hexagonal crystalline ice can be formed by volcanic action. Ice from a theorized
superionic water Superionic water, also called superionic ice or ice XVIII is a phase of water that exists at extremely high temperatures and pressures. In superionic water, water molecules break apart and the oxygen ions crystallize into an evenly spaced lat ...
may possess two crystalline structures. At pressures in excess of such ''superionic ice'' would take on a
body-centered cubic In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties of ...
structure. However, at pressures in excess of the structure may shift to a more stable
face-centered cubic In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties of ...
lattice. It is speculated that superionic ice could compose the interior of ice giants such as Uranus and Neptune.


Friction properties

The low coefficient of friction (" slipperiness") of ice has been attributed to the pressure of an object coming into contact with the ice, melting a thin layer of the ice and allowing the object to glide across the surface. For example, the blade of an ice skate, upon exerting pressure on the ice, would melt a thin layer, providing lubrication between the ice and the blade. This explanation, called " pressure melting", originated in the 19th century. However, it does not account for skating on ice temperatures lower than , which is often skated upon. Also, the effect of pressure melting is too small to account for the reduced friction as commonly experienced. A second theory describing the coefficient of friction of ice suggested that ice molecules at the interface cannot properly bond with the molecules of the mass of ice beneath (and thus are free to move like molecules of liquid water). These molecules remain in a semi-liquid state, providing lubrication regardless of pressure against the ice exerted by any object. However, the significance of this hypothesis is disputed by experiments showing a high
coefficient of friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of t ...
for ice using atomic force microscopy. A third theory is "friction heating", which suggests that friction of the material is the cause of the ice layer melting. However, this theory does not sufficiently explain why ice is slippery when standing still even at below-zero temperatures. A comprehensive theory of ice friction takes into account all the above-mentioned friction mechanisms. This model allows quantitative estimation of the friction coefficient of ice against various materials as a function of temperature and sliding speed. In typical conditions related to winter sports and tires of a vehicle on ice, melting of a thin ice layer due to the frictional heating is the primary reason for the slipperiness. The mechanism controlling the frictional properties of ice is still an active area of scientific study.


Natural formation

The term that collectively describes all of the parts of the Earth's surface where water is in frozen form is the ''
cryosphere ] The cryosphere (from the Ancient Greek, Greek ''kryos'', "cold", "frost" or "ice" and ''sphaira'', "globe, ball") is an all-encompassing term for those portions of Earth's surface where water is in solid form, including sea ice, lake ice, ri ...
.'' Ice is an important component of the global climate, particularly in regard to the water cycle. Glaciers and
snowpack Snowpack forms from layers of snow that accumulate in geographic regions and high elevations where the climate includes cold weather for extended periods during the year. Snowpacks are an important water resource that feed streams and rivers as th ...
s are an important storage mechanism for fresh water; over time, they may sublimate or melt.
Snowmelt In hydrology, snowmelt is surface runoff produced from melting snow. It can also be used to describe the period or season during which such runoff is produced. Water produced by snowmelt is an important part of the annual water cycle in many par ...
is an important source of seasonal fresh water. The
World Meteorological Organization The World Meteorological Organization (WMO) is a specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics. The WMO originated from the Intern ...
defines several kinds of ice depending on origin, size, shape, influence and so on."WMO SEA-ICE NOMENCLATURE"

Multi-language
) ''World Meteorological Organization'' / ''
Arctic and Antarctic Research Institute , image = , image_upright = , alt = , caption = , latin_name = , motto = , founder = , established = , mission = , focus = Researc ...
''. Retrieved 8 April 2012.
Clathrate hydrates are forms of ice that contain gas molecules trapped within its crystal lattice.


On the oceans

Ice that is found at sea may be in the form of
drift ice Drift ice, also called brash ice, is sea ice that is not attached to the shoreline or any other fixed object (shoals, grounded icebergs, etc.).Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer-Verlag. Unlike fast ice, which is "faste ...
floating in the water,
fast ice Fast ice (also called ''land-fast ice'', ''landfast ice'', and ''shore-fast ice'') is sea ice that is "fastened" to the coastline, to the sea floor along shoals or to grounded icebergs.Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer- ...
fixed to a shoreline or
anchor ice Anchor ice is defined by the World Meteorological Organization as "submerged ice attached or anchored to the bottom, irrespective of the nature of its formation". It may also be called bottom-fast ice. Anchor ice is most commonly observed in fast ...
if attached to the sea bottom. Ice which calves (breaks off) from an
ice shelf An ice shelf is a large floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland, Northern Canada, and the Russian Arctic. The ...
or glacier may become an iceberg. Sea ice can be forced together by currents and winds to form pressure ridges up to tall. Navigation through areas of sea ice occurs in openings called "
polynya A polynya () is an area of open water surrounded by sea ice. It is now used as a geographical term for an area of unfrozen seawater within otherwise contiguous pack ice or fast ice. It is a loanword from the Russian полынья (), which r ...
s" or " leads" or requires the use of a special ship called an "
icebreaker An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller ...
".


On land and structures

Ice on land ranges from the largest type called an "
ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at La ...
" to smaller ice caps and
ice field An ice field (also spelled icefield) is a mass of interconnected valley glaciers (also called mountain glaciers or alpine glaciers) on a mountain mass with protruding rock ridges or summits. They are often found in the colder climates and highe ...
s to glaciers and
ice stream An ice stream is a region of fast-moving ice within an ice sheet. It is a type of glacier, a body of ice that moves under its own weight. They can move upwards of a year, and can be up to in width, and hundreds of kilometers in length. They t ...
s to the snow line and
snow field A snow field, snowfield or neve is an accumulation of permanent snow and ice, typically found above the snow line, normally in mountainous and glacial terrain. Glaciers originate in snowfields. The lower end of a glacier is usually free from ...
s.
Aufeis Aufeis, ( ), (German for "ice on top") is a sheet-like mass of layered ice that forms from successive flows of ground or river water during freezing temperatures. This form of ice is also called overflow, icings, or the Russian term, naled. The t ...
is layered ice that forms in Arctic and subarctic stream valleys. Ice, frozen in the stream bed, blocks normal groundwater discharge, and causes the local water table to rise, resulting in water discharge on top of the frozen layer. This water then freezes, causing the water table to rise further and repeat the cycle. The result is a stratified ice deposit, often several meters thick.
Freezing rain Freezing rain is rain maintained at temperatures below freezing by the ambient air mass that causes freezing on contact with surfaces. Unlike a mixture of rain and snow or ice pellets, freezing rain is made entirely of liquid droplets. The rain ...
is a type of winter storm called an
ice storm An ice storm, also known as a glaze event or a silver storm is a type of winter storm characterized by freezing rain. The U.S. National Weather Service defines an ice storm as a storm which results in the accumulation of at least of ice on e ...
where rain falls and then freezes producing a glaze of ice. Ice can also form icicles, similar to stalactites in appearance, or stalagmite-like forms as water drips and re-freezes. The term "ice dam" has three meanings (others discussed below). On structures, an ice dam is the buildup of ice on a sloped roof which stops melt water from draining properly and can cause damage from water leaks in buildings.


On rivers and streams

Ice which forms on moving water tends to be less uniform and stable than ice which forms on calm water.
Ice jam Ice jams occur when a topographic feature of the river causes floating river ice to accumulate and impede further progress downstream with the river current. Ice jams can significantly reduce the flow of a river and cause upstream flooding—som ...
s (sometimes called "ice dams"), when broken chunks of ice pile up, are the greatest ice hazard on rivers. Ice jams can cause flooding, damage structures in or near the river, and damage vessels on the river. Ice jams can cause some
hydropower Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to produce electricity or to power machines. This is achieved by converting the gravitational potential or kinetic energy of a w ...
industrial facilities to completely shut down. An ice dam is a blockage from the movement of a glacier which may produce a
proglacial lake In geology, a proglacial lake is a lake formed either by the damming action of a moraine during the retreat of a melting glacier, a glacial ice dam, or by meltwater trapped against an ice sheet due to isostatic depression of the crust around th ...
. Heavy ice flows in rivers can also damage vessels and require the use of an icebreaker to keep navigation possible. Ice discs are circular formations of ice surrounded by water in a river.
Pancake ice Pancake ice is a form of sea ice that consists of round pieces of ice with diameters ranging from 30 centimetres (12 in) to 3 metres (9.8 ft) and thicknesses up to 10 centimetres (3.9 inches), depending on the local conditions. It forms as a res ...
is a formation of ice generally created in areas with less calm conditions.


On lakes

Ice forms on calm water from the shores, a thin layer spreading across the surface, and then downward. Ice on lakes is generally four types: primary, secondary, superimposed and agglomerate. Primary ice forms first. Secondary ice forms below the primary ice in a direction parallel to the direction of the heat flow. Superimposed ice forms on top of the ice surface from rain or water which seeps up through cracks in the ice which often settles when loaded with snow.
Shelf ice Shelf ice is ice that forms when a portion of a lake surface freezes. It is often then washed upon the shore. The phenomenon is common within the Great Lakes. Formation Shelf ice forms from float ice. Float ice is like drift ice, but seldo ...
occurs when floating pieces of ice are driven by the wind piling up on the windward shore.
Candle ice Rotten ice is a loose term for ice that is melting or structurally disintegrating due to being honeycombed by liquid water, air, or contaminants trapped between the initial growth of ice crystals. It may appear transparent or splotchy grey, and it ...
is a form of
rotten ice Rotten ice is a loose term for ice that is melting or structurally disintegrating due to being honeycombed by liquid water, air, or contaminants trapped between the initial growth of ice crystals. It may appear transparent or splotchy grey, and it ...
that develops in columns perpendicular to the surface of a lake. An
ice shove An ice shove (also known as an ice surge, ice push, ice heave, shoreline ice pileup, ice piling, ice thrust, ice tsunami, ice ride-up, or ''ivu'' in Inupiat) is a surge of ice from an ocean or large lake onto the shore. Ice shoves are caused by ...
occurs when ice movement, caused by ice expansion and/or wind action, occurs to the extent that ice pushes onto the shores of lakes, often displacing sediment that makes up the shoreline.


In the air


Rime

Rime is a type of ice formed on cold objects when drops of water crystallize on them. This can be observed in foggy weather, when the temperature drops during the night. Soft rime contains a high proportion of trapped air, making it appear white rather than transparent, and giving it a density about one quarter of that of pure ice.
Hard rime Rime ice forms when supercooled water liquid droplets freeze onto surfaces. Meteorologists distinguish between three basic types of ice forming on vertical and horizontal surfaces by deposition of supercooled water droplets. There are also interm ...
is comparatively dense.


Pellets

Ice pellets are a form of precipitation consisting of small,
translucent In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions ...
balls of ice. This form of precipitation is also referred to as "sleet" by the United States
National Weather Service The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...
. (In
British English British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the English language in ...
"sleet" refers to a mixture of rain and snow.) Ice pellets are usually smaller than hailstones. They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with
freezing rain Freezing rain is rain maintained at temperatures below freezing by the ambient air mass that causes freezing on contact with surfaces. Unlike a mixture of rain and snow or ice pellets, freezing rain is made entirely of liquid droplets. The rain ...
. The METAR code for ice pellets is ''PL''. Ice pellets form when a layer of above-freezing air is located between above the ground, with sub-freezing air both above and below it. This causes the partial or complete melting of any snowflakes falling through the warm layer. As they fall back into the sub-freezing layer closer to the surface, they re-freeze into ice pellets. However, if the sub-freezing layer beneath the warm layer is too small, the precipitation will not have time to re-freeze, and freezing rain will be the result at the surface. A temperature profile showing a warm layer above the ground is most likely to be found in advance of a
warm front A warm front is a density discontinuity located at the leading edge of a homogeneous warm air mass, and is typically located on the equator-facing edge of an isotherm gradient. Warm fronts lie within broader troughs of low pressure than cold f ...
during the cold season, but can occasionally be found behind a passing
cold front A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure. It often forms behind an extratropical cyclone (to the west in the Northern ...
.


Hail

Like other precipitation, hail forms in storm
cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...
s when supercooled water droplets freeze on contact with condensation nuclei, such as
dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in ho ...
or
dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debris: scattered pieces of waste or remains * Dust: a gener ...
. The storm's
updraft In meteorology, an updraft is a small-scale current of rising air, often within a cloud. Overview Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding regi ...
blows the hailstones to the upper part of the cloud. The updraft dissipates and the hailstones fall down, back into the updraft, and are lifted up again. Hail has a diameter of or more. Within METAR code, GR is used to indicate larger hail, of a diameter of at least and GS for smaller. Stones just larger than
golf ball A golf ball is a special ball designed to be used in the game of golf. Under the rules of golf, a golf ball has a mass no more than , has a diameter not less than , and performs within specified velocity, distance, and symmetry limits. Like g ...
-sized are one of the most frequently reported hail sizes. Hailstones can grow to and weigh more than . In large hailstones,
latent heat Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition. Latent heat can be underst ...
released by further freezing may melt the outer shell of the hailstone. The hailstone then may undergo 'wet growth', where the liquid outer shell collects other smaller hailstones. The hailstone gains an ice layer and grows increasingly larger with each ascent. Once a hailstone becomes too heavy to be supported by the storm's updraft, it falls from the cloud. Hail forms in strong
thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are some ...
clouds, particularly those with intense updrafts, high liquid water content, great vertical extent, large water droplets, and where a good portion of the cloud layer is below freezing . Hail-producing clouds are often identifiable by their green coloration. The growth rate is maximized at about , and becomes vanishingly small much below as supercooled water droplets become rare. For this reason, hail is most common within continental interiors of the mid-latitudes, as hail formation is considerably more likely when the freezing level is below the altitude of . Entrainment of dry air into strong thunderstorms over continents can increase the frequency of hail by promoting evaporational cooling which lowers the freezing level of thunderstorm clouds giving hail a larger volume to grow in. Accordingly, hail is actually less common in the tropics despite a much higher frequency of thunderstorms than in the mid-latitudes because the atmosphere over the tropics tends to be warmer over a much greater depth. Hail in the tropics occurs mainly at higher elevations.


Snow

Snow crystals form when tiny supercooled cloud droplets (about 10 μm in diameter) freeze. These droplets are able to remain liquid at temperatures lower than , because to freeze, a few molecules in the droplet need to get together by chance to form an arrangement similar to that in an ice lattice; then the droplet freezes around this "nucleus". Experiments show that this "homogeneous" nucleation of cloud droplets only occurs at temperatures lower than . In warmer clouds an aerosol particle or "ice nucleus" must be present in (or in contact with) the droplet to act as a nucleus. Our understanding of what particles make efficient ice nuclei is poor – what we do know is they are very rare compared to that cloud condensation nuclei on which liquid droplets form. Clays, desert dust and biological particles may be effective, although to what extent is unclear. Artificial nuclei are used in cloud seeding. The droplet then grows by condensation of water vapor onto the ice surfaces.


Diamond dust

So-called "diamond dust", also known as ice needles or ice crystals, forms at temperatures approaching due to air with slightly higher moisture from aloft mixing with colder, surface-based air. The METAR identifier for diamond dust within international hourly weather reports is ''IC''.


Ablation

Ablation of ice refers to both its
melting Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which inc ...
and its
dissolution Dissolution may refer to: Arts and entertainment Books * ''Dissolution'' (''Forgotten Realms'' novel), a 2002 fantasy novel by Richard Lee Byers * ''Dissolution'' (Sansom novel), a 2003 historical novel by C. J. Sansom Music * Dissolution, in mu ...
. The melting of ice means entails the breaking of hydrogen bonds between the water molecules. The ordering of the molecules in the solid breaks down to a less ordered state and the solid melts to become a liquid. This is achieved by increasing the internal energy of the ice beyond the
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depen ...
. When ice melts it absorbs as much energy as would be required to heat an equivalent amount of water by 80 °C. While melting, the temperature of the ice surface remains constant at 0 °C. The rate of the melting process depends on the efficiency of the energy exchange process. An ice surface in fresh water melts solely by free convection with a rate that depends linearly on the water temperature, ''T'', when ''T'' is less than 3.98 °C, and superlinearly when ''T'' is equal to or greater than 3.98 °C, with the rate being proportional to (T − 3.98 °C)''α'', with ''α'' =  for ''T'' much greater than 8 °C, and α =  for in between temperatures ''T''. In salty ambient conditions, dissolution rather than melting often causes the ablation of ice. For example, the temperature of the
Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...
is generally below the melting point of ablating sea ice. The phase transition from solid to liquid is achieved by mixing
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...
and water molecules, similar to the dissolution of sugar in water, even though the water temperature is far below the melting point of the sugar. Thus the dissolution rate is limited by salt transport whereas melting can occur at much higher rates that are characteristic for heat transport.


Role in human activities

Humans have used ice for cooling and food preservation for centuries, relying on harvesting natural ice in various forms and then transitioning to the mechanical production of the material. Ice also presents a challenge to transportation in various forms and a setting for winter sports.


Cooling

Ice has long been valued as a means of cooling. In 400 BC Iran,
Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, the majority ethnic group in Iran, not to be conflated with the Iranic peoples ** Persian language, an Iranian language of the ...
engineers had already mastered the technique of storing ice in the middle of summer in the desert. The ice was brought in during the winters from nearby mountains in bulk amounts, and stored in specially designed, naturally cooled ''refrigerators'', called yakhchal (meaning ''ice storage''). This was a large underground space (up to 5000 m3) that had thick walls (at least two meters at the base) made of a special mortar called ''
sarooj Sarooj is a traditional water-resistant mortar used in Iranian architecture, used in the construction of bridges, and yakhchal.
'', composed of sand, clay, egg whites, lime, goat hair, and ash in specific proportions, and which was known to be resistant to heat transfer. This mixture was thought to be completely water impenetrable. The space often had access to a
qanat A qanat or kārīz is a system for transporting water from an aquifer or water well to the surface, through an underground aqueduct; the system originated approximately 3,000 BC in what is now Iran. The function is essentially the same across ...
, and often contained a system of
windcatcher A windcatcher, wind tower, or wind scoop ( ar, برجيل ; fa, بادگیر) is a traditional architectural element used to create cross ventilation and passive cooling in buildings. Windcatchers come in various designs: unidirectional, bi ...
s which could easily bring temperatures inside the space down to frigid levels on summer days. The ice was used to chill treats for royalty.


Harvesting

There were thriving industries in 16th–17th century England whereby low-lying areas along the
Thames Estuary The Thames Estuary is where the River Thames meets the waters of the North Sea, in the south-east of Great Britain. Limits An estuary can be defined according to different criteria (e.g. tidal, geographical, navigational or in terms of salini ...
were flooded during the winter, and ice harvested in carts and stored inter-seasonally in insulated wooden houses as a provision to an icehouse often located in large country houses, and widely used to keep fish fresh when caught in distant waters. This was allegedly copied by an Englishman who had seen the same activity in China. Ice was imported into England from Norway on a considerable scale as early as 1823. In the United States, the first cargo of ice was sent from New York City to Charleston, South Carolina, in 1799, and by the first half of the 19th century, ice harvesting had become a big business. Frederic Tudor, who became known as the "Ice King", worked on developing better insulation products for long distance shipments of ice, especially to the tropics; this became known as the
ice trade The ice trade, also known as the frozen water trade, was a 19th-century and early-20th-century industry, centering on the east coast of the United States and Norway, involving the large-scale harvesting, transport and sale of natural ice, an ...
.
Trieste Trieste ( , ; sl, Trst ; german: Triest ) is a city and seaport in northeastern Italy. It is the capital city, and largest city, of the autonomous region of Friuli Venezia Giulia, one of two autonomous regions which are not subdivided into prov ...
sent ice to
Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Medit ...
, Corfu, and
Zante Zakynthos (also spelled Zakinthos; el, Ζάκυνθος, Zákynthos ; it, Zacinto ) or Zante (, , ; el, Τζάντε, Tzánte ; from the Venetian form) is a Greek island in the Ionian Sea. It is the third largest of the Ionian Islands. Za ...
; Switzerland, to France; and Germany sometimes was supplied from
Bavaria Bavaria ( ; ), officially the Free State of Bavaria (german: Freistaat Bayern, link=no ), is a state in the south-east of Germany. With an area of , Bavaria is the largest German state by land area, comprising roughly a fifth of the total lan ...
n lakes. The
Hungarian Parliament The National Assembly ( hu, Országgyűlés, lit=Country Assembly) is the parliament of Hungary. The unicameral body consists of 199 (386 between 1990 and 2014) members elected to 4-year terms. Election of members is done using a semi-propo ...
building used ice harvested in the winter from
Lake Balaton Lake Balaton () is a freshwater lake in the Transdanubian region of Hungary. It is the largest lake in Central Europe, and one of the region's foremost tourist destinations. The Zala River provides the largest inflow of water to the lake, and ...
for air conditioning. Ice houses were used to store ice formed in the winter, to make ice available all year long, and an early type of refrigerator known as an
icebox An icebox (also called a cold closet) is a compact non-mechanical refrigerator which was a common early-twentieth-century kitchen appliance before the development of safely powered refrigeration devices. Before the development of electric refrige ...
was cooled using a block of ice placed inside it. In many cities, it was not unusual to have a regular ice delivery service during the summer. The advent of artificial refrigeration technology has since made delivery of ice obsolete. Ice is still harvested for ice and snow sculpture events. For example, a
swing saw Swing or swinging may refer to: Apparatus * Swing (seat), a hanging seat that swings back and forth * Pendulum, an object that swings * Russian swing, a swing-like circus apparatus * Sex swing, a type of harness for sexual intercourse * Swing ...
is used to get ice for the Harbin International Ice and Snow Sculpture Festival each year from the frozen surface of the
Songhua River The Songhua or Sunghwa River (also Haixi or Xingal, russian: Сунгари ''Sungari'') is one of the primary rivers of China, and the longest tributary of the Amur. It flows about from the Changbai Mountains on the China–North Korea bo ...
.


Mechanical production

Ice is now produced on an industrial scale, for uses including food storage and processing, chemical manufacturing, concrete mixing and curing, and consumer or packaged ice.
ASHRAE The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE ) is an American professional association seeking to advance heating, ventilation, air conditioning and refrigeration The term refrigeration refers to the ...
. "Ice Manufacture". ''2006
ASHRAE Handbook The ASHRAE Handbook is the four-volume flagship publication of the nonprofit technical organization ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers). This Handbook is considered the most comprehensive and autho ...
: Refrigeration.'' Inch-Pound Edition. .
Most commercial
icemaker An icemaker, ice generator, or ice machine may refer to either a consumer device for making ice, found inside a home freezer; a stand-alone appliance for making ice, or an industrial machine for making ice on a large scale. The term "ice machin ...
s produce three basic types of fragmentary ice: flake, tubular and plate, using a variety of techniques. Large batch ice makers can produce up to 75 tons of ice per day. In 2002, there were 426 commercial ice-making companies in the United States, with a combined value of shipments of $595,487,000. Home refrigerators can also make ice with a built in
icemaker An icemaker, ice generator, or ice machine may refer to either a consumer device for making ice, found inside a home freezer; a stand-alone appliance for making ice, or an industrial machine for making ice on a large scale. The term "ice machin ...
, which will typically make ice cubes or crushed ice. Stand-alone icemaker units that make ice cubes are often called ice machines.


Transportation

Ice can present challenges to safe transportation on land, sea and in the air.


Land travel

Ice forming on
road A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are many types of ...
s is a dangerous winter hazard.
Black ice Black ice, sometimes called clear ice, is a thin coating of glaze ice on a surface, especially on streets. The ice itself is not black, but visually transparent, allowing the often black road below to be seen through it. The typically low level ...
is very difficult to see, because it lacks the expected frosty surface. Whenever there is freezing rain or snow which occurs at a temperature near the melting point, it is common for ice to build up on the
window A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent mat ...
s of vehicles. Driving safely requires the removal of the ice build-up. Ice scrapers are tools designed to break the ice free and clear the windows, though removing the ice can be a long and laborious process. Far enough below the freezing point, a thin layer of ice crystals can form on the inside surface of windows. This usually happens when a vehicle has been left alone after being driven for a while, but can happen while driving, if the outside temperature is low enough. Moisture from the driver's breath is the source of water for the crystals. It is troublesome to remove this form of ice, so people often open their windows slightly when the vehicle is parked in order to let the moisture dissipate, and it is now common for cars to have rear-window defrosters to solve the problem. A similar problem can happen in homes, which is one reason why many colder regions require double-pane windows for insulation. When the outdoor temperature stays below freezing for extended periods, very thick layers of ice can form on
lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...
s and other bodies of water, although places with flowing water require much colder temperatures. The ice can become thick enough to drive onto with
automobile A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarde ...
s and
truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...
s. Doing this safely requires a thickness of at least 30 cm (one foot).


Water-borne travel

For ships, ice presents two distinct hazards. First, spray and freezing rain can produce an ice build-up on the superstructure of a vessel sufficient to make it unstable, and to require it to be hacked off or melted with steam hoses. Second, icebergs – large masses of ice floating in water (typically created when glaciers reach the sea) – can be dangerous if struck by a ship when underway. Icebergs have been responsible for the sinking of many ships, the most famous being the ''Titanic''. For
harbor A harbor (American English), harbour (British English; see spelling differences), or haven is a sheltered body of water where ships, boats, and barges can be docked. The term ''harbor'' is often used interchangeably with ''port'', which is a ...
s near the
pole Pole may refer to: Astronomy *Celestial pole, the projection of the planet Earth's axis of rotation onto the celestial sphere; also applies to the axis of rotation of other planets *Pole star, a visible star that is approximately aligned with the ...
s, being ice-free, ideally all year long, is an important advantage. Examples are
Murmansk Murmansk (Russian: ''Мурманск'' lit. "Norwegian coast"; Finnish: ''Murmansk'', sometimes ''Muurmanski'', previously ''Muurmanni''; Norwegian: ''Norskekysten;'' Northern Sámi: ''Murmánska;'' Kildin Sámi: ''Мурман ланнҍ'') ...
(Russia), Petsamo (Russia, formerly Finland), and
Vardø ( fi, Vuoreija, fkv, Vuorea, se, Várggát) is a municipality in Troms og Finnmark county in the extreme northeastern part of Norway. Vardø is the easternmost town in Norway, more to the east than Saint Petersburg or Istanbul. The administr ...
(Norway). Harbors which are not ice-free are opened up using
icebreaker An icebreaker is a special-purpose ship or boat designed to move and navigate through ice-covered waters, and provide safe waterways for other boats and ships. Although the term usually refers to ice-breaking ships, it may also refer to smaller ...
s.


Air travel

For aircraft, ice can cause a number of dangers. As an aircraft climbs, it passes through air layers of different temperature and humidity, some of which may be conducive to ice formation. If ice forms on the wings or control surfaces, this may adversely affect the flying qualities of the aircraft. During the first non-stop flight across the Atlantic, the British aviators Captain John Alcock and Lieutenant
Arthur Whitten Brown Lieutenant-Colonel Sir Arthur Whitten Brown, (23 July 1886 – 4 October 1948) was a British military officer and aviator who flew as navigator of the first successful non-stop transatlantic flight with pilot John Alcock in June 1919. Biogr ...
encountered such icing conditions – Brown left the cockpit and climbed onto the wing several times to remove ice which was covering the engine air intakes of the
Vickers Vimy The Vickers Vimy was a British heavy bomber aircraft developed and manufactured by Vickers Limited. Developed during the latter stages of the First World War to equip the Royal Flying Corps (RFC), the Vimy was designed by Reginald Kirshaw "Rex" ...
aircraft they were flying. One vulnerability effected by icing that is associated with reciprocating internal combustion engines is the carburetor. As air is sucked through the carburetor into the engine, the local air pressure is lowered, which causes adiabatic cooling. Thus, in humid near-freezing conditions, the carburetor will be colder, and tend to ice up. This will block the supply of air to the engine, and cause it to fail. For this reason, aircraft reciprocating engines with carburetors are provided with carburetor air intake heaters. The increasing use of fuel injection—which does not require carburetors—has made "carb icing" less of an issue for reciprocating engines. Jet engines do not experience carb icing, but recent evidence indicates that they can be slowed, stopped, or damaged by internal icing in certain types of atmospheric conditions much more easily than previously believed. In most cases, the engines can be quickly restarted and flights are not endangered, but research continues to determine the exact conditions which produce this type of icing, and find the best methods to prevent, or reverse it, in flight.


Recreation and sports

Ice also plays a central role in winter recreation and in many sports such as
ice skating Ice skating is the self-propulsion and gliding of a person across an ice surface, using metal-bladed ice skates. People skate for various reasons, including recreation (fun), exercise, competitive sports, and commuting. Ice skating may be per ...
,
tour skating Tour skating is recreational long distance ice skating on natural ice. It is particularly popular in the Netherlands and the Nordic countries. It is becoming more popular in areas of North America such as New England, Southcentral Alaska, and No ...
,
ice hockey Ice hockey (or simply hockey) is a team sport played on ice skates, usually on an ice skating rink with lines and markings specific to the sport. It belongs to a family of sports called hockey. In ice hockey, two opposing teams use ice h ...
, bandy,
ice fishing Ice fishing is the practice of catching fish with lines and fish hooks or spears through an opening in the ice on a frozen body of water. Ice fishers may fish in the open or in heated enclosures, some with bunks and amenities. Shelters Longe ...
, ice climbing,
curling Curling is a sport in which players slide stones on a sheet of ice toward a target area which is segmented into four concentric circles. It is related to bowls, boules, and shuffleboard. Two teams, each with four players, take turns slidi ...
,
broomball Broomball is a both a recreational and organized competitive winter team sport played on ice or snow and is played either indoors or outdoors, depending on climate and location. It is a ball sport and is most popularly played in Canada and the ...
and sled racing on
bobsled Bobsleigh or bobsled is a team winter sport that involves making timed runs down narrow, twisting, banked, iced tracks in a gravity-powered sleigh. International bobsleigh competitions are governed by the International Bobsleigh and Skeleton Feder ...
, luge and skeleton. Many of the different sports played on ice get international attention every four years during the
Winter Olympic Games The Winter Olympic Games (french: link=no, Jeux olympiques d'hiver) is a major international multi-sport event held once every four years for sports practiced on snow and ice. The first Winter Olympic Games, the 1924 Winter Olympics, were h ...
. A sort of sailboat on blades gives rise to
ice yachting An iceboat (occasionally spelled ice boat or traditionally called an ice yacht) is a recreational or competition sailing craft supported on metal runners for traveling over ice. One of the runners is steerable. Originally, such craft were boats ...
. Another sport is
ice racing Ice racing is a form of racing that uses cars, motorcycles, snowmobiles, all-terrain vehicles, or other motorized vehicles. Ice racing takes place on frozen lakes or rivers, or on groomed frozen lots. As cold weather is a requirement for natural ...
, where drivers must speed on lake ice, while also controlling the skid of their vehicle (similar in some ways to dirt track racing). The sport has even been modified for
ice rink An ice rink (or ice skating rink) is a frozen body of water and/or an artificial sheet of ice created using hardened chemicals where people can ice skate or play winter sports. Ice rinks are also used for exhibitions, contests and ice shows. The ...
s.


Other uses


As thermal ballast

* Ice is used to cool and preserve food in
icebox An icebox (also called a cold closet) is a compact non-mechanical refrigerator which was a common early-twentieth-century kitchen appliance before the development of safely powered refrigeration devices. Before the development of electric refrige ...
es. * Ice cubes or
crushed ice An ice cube is a small piece of ice, which is typically rectangular as viewed from above and trapezoidal as viewed from the side. Ice cubes are products of mechanical refrigeration and are usually produced to cool beverages. They may be produ ...
can be used to cool drinks. As the ice melts, it absorbs heat and keeps the drink near . * Ice can be used as part of an air conditioning system, using battery- or
solar-powered Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Photovoltaic cells convert light into an electric current using the photovoltaic ef ...
fans to blow hot air over the ice. This is especially useful during
heat wave A heat wave, or heatwave, is a period of excessively hot weather, which may be accompanied by high humidity, especially in oceanic climate countries. While definitions vary, a heat wave is usually measured relative to the usual climate in the ...
s when power is out and standard (electrically powered) air conditioners do not work. * Ice can be used (like other cold packs) to reduce swelling (by decreasing blood flow) and pain by pressing it against an area of the body.


As structural material

* Engineers used the substantial strength of pack ice when they constructed Antarctica's first floating
ice pier An ice pier or ice wharf is a man-made structure used to assist the unloading of ships in Antarctica. It is constructed by pumping seawater into a contained area and allowing the water to freeze. By repeating this procedure several times, additio ...
in 1973. Such ice piers are used during cargo operations to load and offload ships. Fleet operations personnel make the floating pier during the winter. They build upon naturally occurring frozen seawater in
McMurdo Sound McMurdo Sound is a sound in Antarctica. It is the southernmost navigable body of water in the world, and is about from the South Pole. Captain James Clark Ross discovered the sound in February 1841, and named it after Lt. Archibald McMurdo ...
until the dock reaches a depth of about . Ice piers have a lifespan of three to five years. * Structures and ice sculptures are built out of large chunks of ice or by spraying waterMakkonen, L. (1994) "Ice and Construction". E & FN Spon, London. . The structures are mostly ornamental (as in the case with ice castles), and not practical for long-term habitation. Ice hotels exist on a seasonal basis in a few cold areas. Igloos are another example of a temporary structure, made primarily from snow. * In cold climates, roads are regularly prepared on iced-over lakes and archipelago areas. Temporarily, even a railroad has been built on ice. * During World War II, Project Habbakuk was an Allied programme which investigated the use of
pykrete Pykrete is a frozen ice composite, originally made of approximately 14% sawdust or some other form of wood pulp (such as paper) and 86% ice by weight (6 to 1 by weight). During World War II, Geoffrey Pyke proposed it as a candidate material fo ...
(wood fibers mixed with ice) as a possible material for warships, especially aircraft carriers, due to the ease with which a vessel immune to torpedoes, and a large deck, could be constructed by ice. A small-scale prototype was built, but the need for such a vessel in the war was removed prior to building it in full-scale. * Ice has even been used as the material for a variety of musical instruments, for example by percussionist
Terje Isungset Terje Isungset (born May 4, 1964) is a Norwegian drummer. From his background in jazz and traditional Scandinavian music, he has designed musical instruments from non-traditional materials, including ice. Career Isungset was raised in Geil ...
.


Non-water

The solid phases of several other volatile substances are also referred to as ''ices''; generally a volatile is classed as an ice if its melting point lies above or around 100 K. The best known example is
dry ice Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...
, the solid form of
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
. A "magnetic analogue" of ice is also realized in some insulating magnetic materials in which the magnetic moments mimic the position of protons in water ice and obey energetic constraints similar to the Bernal-Fowler ice rules arising from the
geometrical frustration In condensed matter physics, the term geometrical frustration (or in short: frustration) refers to a phenomenon where atoms tend to stick to non-trivial positions or where, on a regular crystal lattice, conflicting inter-atomic forces (each one favo ...
of the proton configuration in water ice. These materials are called
spin ice A spin ice is a magnetic substance that does not have a single minimal-energy state. It has magnetic moments (i.e. "spin") as elementary degrees of freedom which are subject to frustrated interactions. By their nature, these interactions preven ...
.


See also

* * * * * * *


References


External links


Webmineral listing for Ice



Estimating the bearing capacity of ice




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