A satellite composite image of Antarctica

An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (19,000 sq mi),^[1] thus also known as continental glacier.^[2] The only current ice sheets are in Antarctica and Greenland; during the last glacial period at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much of North America, the Weichselian ice sheet covered northern Europe and the Patagonian Ice Sheet covered southern South America.

Ice sheets are bigger than ice shelves or alpine glaciers. Masses of ice covering less than 50,000 km² are termed an ice cap. An ice cap will typically feed a series of glaciers around its periphery.

Although the surface is cold, the base of an ice sheet is generally warmer due to geothermal heat. In places, melting occurs and the melt-water lubricates the ice sheet so that it flows more rapidly. This process produces fast-flowing channels in the ice sheet — these are ice streams.

The present-day polar ice sheets are relatively young in geological terms. The Antarctic Ice Sheet first formed as a small ice cap (maybe several) in the early Oligocene, but retreating and advancing many times until the Pliocene, when it came to occupy almost all of Antarctica. The Greenland ice sheet did not develop at all until the late Pliocene, but apparently developed very rapidly with the first continental glaciation. This had the unusual effect of allowing fossils of plants that once grew on present-day Greenland to be much better preserved than with the slowly forming Antarctic ice sheet.

Antarctic ice sheet[link]

The Antarctic ice sheet is the largest single mass of ice on Earth. It covers an area of almost 14 million km² and contains 30 million km³ of ice. Around 90% of the fresh water on the Earth's surface is held in the ice sheet, and, if melted, would cause sea levels to rise by 61.1 metres.^[3] The continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05°C/decade since 1957.^[4]

The Antarctic ice sheet is divided by the Transantarctic Mountains into two unequal sections called the East Antarctic ice sheet (EAIS) and the smaller West Antarctic Ice Sheet (WAIS). The EAIS rests on a major land mass but the bed of the WAIS is, in places, more than 2,500 meters below sea level. It would be seabed if the ice sheet were not there. The WAIS is classified as a marine-based ice sheet, meaning that its bed lies below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea.

Greenland ice sheet[link]

Map of Greenland^[5]

The Greenland ice sheet occupies about 82% of the surface of Greenland, and if melted would cause sea levels to rise by 7.2 metres.^[3] Estimated changes in the mass of Greenland's ice sheet suggest it is melting at a rate of about 239 cubic kilometres (57.3 cubic miles) per year.^[6] These measurements came from NASA's Gravity Recovery and Climate Experiment (GRACE) satellite, launched in 2002, as reported by BBC News in August 2006.^[7]

Ice sheet dynamics[link]

Ice movement is dominated by the motion of glaciers, whose activity is determined by a number of processes.^[8] Their motion is the result of cyclic surges interspersed with longer periods of inactivity, on both hourly and centennial time scales.

Predicted effects of global warming[link]

The Greenland, and probably the Antarctic, ice sheets have been losing mass recently, because losses by melting and outlet glaciers exceed accumulation of snowfall. According to the Intergovernmental Panel on Climate Change (IPCC), loss of Antarctic and Greenland ice sheet mass contributed, respectively, about 0.21 ± 0.35 and 0.21 ± 0.07 mm/year to sea level rise between 1993 and 2003.^[9]

The IPCC projects that ice mass loss from melting of the Greenland ice sheet will continue to outpace accumulation of snowfall. Accumulation of snowfall on the Antarctic ice sheet is projected to outpace losses from melting. However, loss of mass on the Antarctic sheet may continue, if there is sufficient loss to outlet glaciers. In the words of the IPCC, "Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude." More research work is therefore required in order to improve the reliability of predictions of ice-sheet response on global warming.

The effects on ice formations of an increasing in temperature will accelerate. When ice is melted away less light from the sun will be reflected back into space and more will be absorbed by the ocean water causing further rises in temperature. This positive feedback system will could become independent of climate change past a certain point which will cause huge losses of ice to the icecaps.

References[link]

External links[link]

• United Nations Environment Programme: Global Outlook for Ice and Snow
• http://www.nasa.gov/vision/earth/environment/ice_sheets.html

A natural block of (water) ice

Snowflakes (ice crystals) by Wilson Bentley, 1902

Ice is water frozen into the solid state. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions. The addition of other materials such as soil may further alter the appearance.

Ice appears in nature in forms of snowflakes, hail, icicles, glaciers, pack ice, and entire polar ice caps. It is an important component of the global climate, and plays an important role in the water cycle. Furthermore, ice has numerous cultural applications, from ice cooling of drinks to winter sports and the art of ice sculpting.

The molecules in solid ice may be arranged in different ways, called phases, depending on the temperature and pressure. Usually ice is the phase known as ice I_h, which is the most abundant of the varying solid phases on the Earth's surface. The most common phase transition to ice I_h occurs when liquid water is cooled below 0°C (273.15K, 32°F) at standard atmospheric pressure. It can also deposit from vapour with no intervening liquid phase, such as in the formation of frost.

The word is derived from Old English īs, which in turn stems from Proto-Germanic isaz.

Characteristics[link]

Crystal structure of hexagonal ice. Grey dashed lines indicate hydrogen bonds.

As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered a mineral.^[1] It possesses a regular crystalline structure based on the molecule of water, which consists of a single oxygen atom covalently 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. It is a weak bond, but is critical in controlling the structure of both water and ice.

An unusual property of ice frozen at atmospheric pressure is that the solid is approximately 8.3% less dense than liquid water. The density of ice is 0.9167 g/cm³ at 0 °C, whereas water has a density of 0.9998 g/cm³ at the same temperature. Liquid water is densest, essentially 1.00 g/cm³, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals^[2] of ice 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).^[3]

The effect of expansion during freezing can be dramatic, and is a basic cause of freeze-thaw weathering of rock in nature. 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, then leak water after thawing.

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. It has been argued that without this property natural bodies of water would freeze, in some cases permanently, from the bottom up,^[4] resulting in a loss of bottom-dependent animal and plant life in fresh and sea water. Sufficiently thin ice sheets 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 and Minke whales.^[5]

When ice melts, it absorbs as much energy 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 for 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.^[6]

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.^[6]

Slipperiness[link]

Frozen waterfall in southeast New York

It has long been believed that ice is slippery because the pressure of an object in contact with it causes a thin layer to melt. For example, the blade of an ice skate, exerting pressure on the ice, melts a thin layer, providing lubrication between the ice and the blade. This explanation, called "pressure melting", originated in 19th century. This however did not account for skating on ice temperatures lower than -3.5 °C, whereas skaters often skate on lower temperature ice. In 20th century an alternative explanation, called "friction heating" was proposed, whereby friction of the material was causing the ice layer melting. However, this theory also failed to explain skating at low temperature. In fact, neither explanation explained why ice is slippery when standing still even at below-zero temperatures.^[7]

This explanation has come into doubt with the proposal that ice molecules in contact with air 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 semiliquid state, providing lubrication regardless of pressure against the ice exerted by any object.^[8]

Formation[link]

Feather ice on the plateau near Alta, Norway. The crystals form at temperatures below −30 °C (i.e. −22 °F).

Ice that is found at sea may be in the form of sea ice, pack ice, or icebergs. The term that collectively describes all of the parts of the Earth's surface where water is in frozen form is the cryosphere. Ice is an important component of the global climate, particularly in regard to the water cycle. Glaciers and snowpacks are an important storage mechanism for fresh water; over time, they may sublimate or melt. Snowmelt is often an important source of seasonal fresh water.

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 is comparatively denser.

Aufeis 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.

Ice can also form icicles, similar to stalactites in appearance, or stalagmite-like forms as water drips and re-freezes.

Clathrate hydrates are forms of ice that contain gas molecules trapped within its crystal lattice.

Pancake ice is a formation of ice generally created in areas with less calm conditions.

Candle Ice is a form of Rotten Ice that develops in columns perpendicular to the surface of a lake.

Ice discs are circular formations of ice surrounded by water in a river.

The World Meteorological Organization defines several kinds of ice depending on origin, size, shape, influence and so on.^[9]

Ice pellets[link]

An accumulation of ice pellets

Ice pellets are a form of precipitation consisting of small, translucent balls of ice. This form of precipitation is also known as sleet.^[10] Ice pellets are usually (but not always) smaller than hailstones.^[11] They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with freezing rain. The METAR code for ice pellets is PL.^[12]

Ice pellets form when a layer of above-freezing air is located between 1,500 metres (4,900 ft) and 3,000 metres (9,800 ft) 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 during the cold season,^[13] but can occasionally be found behind a passing cold front.

Hail[link]

A large hailstone, about 6 cm (2.36 in) in diameter

Like other precipitation, hail forms in storm clouds when supercooled water droplets freeze on contact with condensation nuclei, such as dust or dirt. The storm's updraft 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 5 millimetres (0.20 in) or more.^[14] Within METAR code, GR is used to indicate larger hail, of a diameter of at least 6.4 millimetres (0.25 in). GR is derived from the French word grêle. Smaller-sized hail, as well as snow pellets, use the coding of GS, which is short for the French word grésil.^[12] Stones just larger than golf ball-sized are one of the most frequently reported hail sizes.^[15] Hailstones can grow to 15 centimetres (6 in) and weigh more than .5 kilograms (1.1 lb).^[16] In large hailstones, latent heat 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.^[17] 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.^[18]

Hail forms in strong thunderstorm 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 0 °C (32 °F).^[14] Hail-producing clouds are often identifiable by their green coloration.^[19][20] The growth rate is maximized at about −13 °C (9 °F), and becomes vanishingly small much below −30 °C (−22 °F) 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 11,000 feet (3,400 m).^[21] 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.^[22]

Snowflakes[link]

Snowflake viewed in an optical microscope

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 −18 °C (255 K; −0 °F), 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 −35 °C (238 K; −31 °F).^[23] 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,^[24] although to what extent is unclear. Artificial nuclei include particles of silver iodide and dry ice, and these are used to stimulate precipitation in cloud seeding.^[25]

Once a droplet has frozen, it grows in the water-supersaturated air, when the temperature remains below the freezing point. The droplet then grows by condensation of water vapor onto the ice surfaces. Air saturation with water is maintained by continuous simultaneous evaporation of water droplets. Thus ice crystals grow at the expense of water droplets in a process called the Wegner-Bergeron-Findeison process. These large crystals are an efficient source of precipitation, since they fall through the atmosphere due to their weight, and may collide and aggregate in clusters. These aggregates are snowflakes, and are usually the type of ice particle that falls to the ground.^[26] Guinness World Records list the world’s largest snowflakes as those of January 1887 at Fort Keogh, Montana; allegedly one measured 38 cm (15 inches) wide.^[27]

The exact details of the sticking mechanism remain controversial. Possibilities include mechanical interlocking, sintering, electrostatic attraction as well as the existence of a "sticky" liquid-like layer on the crystal surface. The individual ice crystals often have hexagonal symmetry. Although the ice is clear, scattering of light by the crystal facets and hollows/imperfections mean that the crystals often appear white in color due to diffuse reflection of the whole spectrum of light by the small ice particles.^[28] The shape of the snowflake is determined broadly by the temperature and humidity at which it is formed.^[26] Rarely, at a temperature of around −2 °C (28 °F), snowflakes can form in threefold symmetry — triangular snowflakes.^[29] The most common snow particles are visibly irregular, although near-perfect snowflakes may be more common in pictures because they are more visually appealing. It is unlikely that any two snowflakes are alike due to the estimated 10¹⁹ (10 quintillion) water molecules which make up a typical snowflake,^[30] which grow at different rates and in different patterns depending on the changing temperature and humidity within the atmosphere that the snowflake falls through on its way to the ground.^[31] The METAR code for snow is SN, while snow showers are coded SHSN.^[12]

Diamond dust[link]

Diamond dust, also known as ice needles or ice crystals, forms at temperatures approaching −40 °F (−40 °C) due to air with slightly higher moisture from aloft mixing with colder, surface based air.^[32] The METAR identifier for diamond dust within international hourly weather reports is IC.^[12]

Production[link]

Harvesting ice on Lake Saint Clair in Michigan, c. 1905

B&W film of 1919 ice harvest at Pocono Manor in the Poconos

An ice manufacturing plant in East Midnapore, India

Ice is now mechanically produced on a large scale, but before refrigeration was developed ice was harvested from natural sources for human use.

Ice harvesting[link]

Ice has long been valued as a means of cooling. In 400 BC Iran, Persian 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 out of a special mortar called sārooj, 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, and often contained a system of windcatchers which could easily bring temperatures inside the space down to frigid levels on summer days. The ice was used to chill treats for royalty.

There were thriving industries in the 16/17th century in UK whereby low lying areas along the River Thames estuary 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 copied from the Chinese who had been doing it for thousands of years. This was reportedly copied by an Englishman who had seen the same activity in China.^[33] Ice was imported into England from Norway on a considerable scale as early as 1823.^[34]

In the United States, the first cargo of ice was sent from New York City to Charleston, South Carolina in 1799,^[34] and by the first half of the 19th century, ice harvesting had become big business. Frederic Tudor, who became known as the “Ice King,” worked on developing better insulation products for the long distance shipment of ice, especially to the tropics; this became known as the ice trade.

Triest sent ice to Egypt, Corfu, and Zante; Switzerland sent it to France; and Germany sometimes was supplied from Bavarian lakes.^[34]

Until recently,^[when?] the Hungarian Parliament building used ice harvested in the winter from Lake Balaton for air conditioning. Icehouses were used to store ice formed in the winter, to make ice available all year long, and early refrigerators were known as iceboxes, because they had a block of ice in them. 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 harvesting is still done for ice and snow sculpture events. A swing saw is used to get ice out of the river for the Harbin International Ice and Snow Sculpture Festival each year. A swing saws is used to cut ice out from the frozen surface of the Songhua River.^[35] Many ice sculptures are made from the ice.

Commercial production[link]

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.^[36] Most commercial ice makers produce three basic types of fragmentary ice: flake, tubular and plate, using a variety of techniques.^[36] Large batch ice makers can produce up to 75 tons of ice per day.^[37]

Ice production is a large business; in 2002, there were 426 commercial ice-making companies in the United States, with a combined value of shipments of $595,487,000.^[38]

For small-scale ice production, many modern home refrigerators can also make ice with a built in icemaker, which will typically make ice cubes or crushed ice. Stand-alone icemaker units that make ice cubes are often called ice machines.

Uses[link]

Sports[link]

Ice sailing on the Żnin Small Lake

Ice also plays a central role in winter recreation and in many sports such as ice skating, tour skating, ice hockey, ice fishing, ice climbing, curling, broomball and sled racing on bobsled, luge and skeleton. Many of the different sports played on ice get international attention every four years during the Winter Olympic Games.

A sort of sailboat on blades gives rise to ice yachting. The human quest for excitement has even led to ice racing, 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 rinks.

Other uses[link]

• Ice cubes or crushed ice can be used to cool drinks. As the ice melts, it absorbs heat and keeps the drink near 0 °C (32 °F).
• Ice can be used to reduce swelling (by decreasing blood flow) and pain by pressing it against an area of the body.^[39]

Ice pier during 1983 cargo operations. McMurdo Station, Antarctica

• Engineers used formidable strength of pack ice when they constructed Antarctica's first floating ice pier in 1973.^[40] 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 until the dock reaches a depth of about 22 feet (6.7 m). Ice piers have a lifespan of three to five years.
• Structures and ice sculptures are built out of large chunks of ice. 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.
• During World War II, Project Habbakuk was a British programme which investigated the use of pykrete (wood fibers mixed with ice) as a possible material for warships, especially aircraft carriers, due to the ease with which a large deck could be constructed, but the idea was given up when there were not enough funds for construction of a prototype.
• Ice can be used to start a fire by carving it into a lens which will focus sunlight onto kindling. A fire will eventually start.^[41]
• Ice has even been used as the material for a variety of musical instruments, for example by percussionist Terje Isungset.^[42]
• Ice was once used to cool refrigerators in the 19th century, which is reflected in the name "iceboxes."
• Ice can be used to store cooling, which has the same effect as storing electricity Thermal energy storageAir conditioning

Ice and transportation[link]

U.S. Coast Guard icebreakers near McMurdo Station, February 2002

Ice can also be an obstacle; for harbors near the poles, being ice-free is an important advantage; ideally, all year long. Examples are Murmansk (Russia), Petsamo (Russia, formerly Finland) and Vardø (Norway). Harbors which are not ice-free are opened up using icebreakers.

Ice forming on roads is a dangerous winter hazard. Black ice 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 windows 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 lakes and other bodies of water, although places with flowing water require much colder temperatures. The ice can become thick enough to drive onto with automobiles and trucks. Doing this safely requires a thickness of at least 30 cm (one foot).

For ships, ice presents two distinct hazards. 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. And 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 probably being the Titanic.

Ice formation on window glass of high altitude flying airplane

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 of the Atlantic, the British aviators Captain John Alcock and Lieutenant Arthur Whitten Brown 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 aircraft they were flying.

A particular icing vulnerability 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. So, 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.

Phases[link]

Ice may be any one of the 15 known solid phases of water.

Most liquids freeze at a higher temperature under pressure, because the pressure helps to hold the molecules together. However, the strong hydrogen bonds in water make it different: water freezes at a temperature below 0 °C under a pressure higher than 1 atm (0.10 MPa). Consequently, water also remains frozen at a temperature above 0 °C under a pressure lower than 1 atm. The melting of ice under high pressures is thought to contribute to the movement of glaciers.

Ice, water, and water vapour can coexist at the triple point, which is exactly 0.01 °C or 273.16 K (by definition) at a pressure of 611.73 Pa. 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.^[43]

Subjected to higher pressures and varying temperatures, ice can form in fifteen separate known phases. With care all these phases except ice X can be recovered at ambient pressure and low temperature. The types are differentiated by their crystalline structure, ordering and density. There are also two metastable phases of ice under pressure, both fully hydrogen-disordered; these are IV and XII. Ice XII was discovered in 1996. In 2006, XIII and XIV were discovered.^[44] Ices XI, XIII, and XIV are hydrogen-ordered forms of ices I_h, V, and XII respectively. In 2009, ice XV was found at extremely high pressures and −143 °C.^[45] At even higher pressures, ice is predicted to become a metal; this has been variously estimated to occur at 1.55 TPa^[46] or 5.62 TPa.^[47]

As well as crystalline forms, solid water can exist in amorphous states as amorphous solid water (ASW), low-density amorphous ice (LDA), high-density amorphous ice (HDA), very high-density amorphous ice (VHDA) and hyperquenched glassy water (HGW).

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 via volcanic action.^[48]

Log-lin pressure-temperature phase diagram of water. The Roman numerals correspond to some ice phases listed below.

Other ices[link]

Detail of an ice cube

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 ~100 K. The best known example is dry ice, the solid form of carbon dioxide.

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 of the proton configuration in water ice. These materials are called spin ice.

See also[link]

• Density of ice versus water
• Ice famine
• Pumpable ice technology

References[link]

External links[link]

Look up ice in Wiktionary, the free dictionary.

Wikimedia Commons has media related to: Ice

• The National Snow and Ice Data Center, based in the United States
• The phase diagram of water, including the ice variants
• Webmineral listing for Ice
• MinDat.org listing and location data for Ice
• The physics of ice
• The phase diagrams of water with some high pressure diagrams
• 'Unfreezable' water, 'bound water' and water of hydration
• Electromechanical properties of ice
• Estimating the maximum thickness of an ice layer
• Sandia's Z machine creates ice in nanoseconds
• Amazing ice at Lac Leman
• The Surprisingly Cool History of Ice

Ugly Casanova is an American indie rock band carried on Sub Pop Records. The band has released one album, Sharpen Your Teeth.

Career[link]

According to the Ugly Casanova website, in 1998 a man named Edgar E.Graham, a.k.a. "Ugly Casanova", impressed himself upon the band Modest Mouse while backstage at a concert in Denver, Colorado. After some prodding, he shared his work with the band and began performing it early before shows while some people were milling around. Whenever he completed these performances, he retreated quickly with a look of anger and shame. After a time, a few small recordings were created, after which Edgar vanished. Isaac Brock of Modest Mouse later recorded his songs in hopes that Graham would resurface in the music scene.^[1] Isaac Brock has since revealed that Edgar Graham was "a fiction thing that [Brock] started awhile back to eliminate [himself] from the band," to escape having to do interviews.^[2] Two pieces of evidence exist that suggest that the story was false: Modest Mouse's 1997 EP The Fruit That Ate Itself was credited to having been under the production company Ugly Casanova, which suggested it was a name Brock made up to retain creative control and publishing rights to his music while under a major label. Secondly, "Ugly Casanova" was the title of a song Brock wrote around 1993. The band lineup as of the 180° South: Conquerers of the Useless soundtrack consists of Isaac Brock, Eric Judy, Tom Peloso, and Joe Plummer of Modest Mouse, as well as Clay Jones, who worked as an engineer on Modest Mouse's fifth album, We Were Dead Before The Ship Even Sank. The band's lineup for Sharpen Your Teeth consisted of Isaac Brock, Tim Rutili (Califone, Red Red Meat), Pall Jenkins (The Black Heart Procession), John Orth (Holopaw), and Brian Deck (Red Red Meat).

One key difference between Ugly Casanova in comparison to Modest Mouse is the more stripped-down nature of the songs. The lack of overdubbed vocals on some of the tracks is particularly significant because Brock is known for having a slight lisp which he is very uncomfortable with and often covered up on Modest Mouse recordings via double tracking and distortion. Ugly Casanova mixes indie rock with hints of country and folk, ranging from acoustic ballads (Hotcha Girls) to more bizarre with piercing vocals (Diamonds on the Face of Evil). The mood created by Ugly Casanova's songs reflects the enigma that is its creator, Edgar Graham.^[1]

Two tracks released by Ugly Casanova, "Baby's Clean Conscience" and "Parasites", appear earlier as unreleased demos of Modest Mouse in the Paracite Sessions purportedly recorded in 1993 at Calvin Johnson's Dub Narcotic Studio. In 1997 the fourth Magic Eye Single (each one named after its color of vinyl) included To Roads To Go ^[3] on the apparently now defunct Magic Eye Records, however, this was an entirely different incarnation of Ugly Casanova of Isaac Brock, Steve Dukage, and John Atkins of 764-Hero.

Rumors of new Ugly Casanova material have come and gone over recent years, but no substantial news regarding the band had surfaced until it was announced that Ugly Casanova would contribute to the soundtrack for the 2010 documentary 180 Degrees South: Conquerors of the Useless. The soundtrack featured eight new Ugly Casanova songs as well as a redone version of "Hotcha Girls" from Sharpen Your Teeth.^[4]

Discography[link]

• "Magic Eye Single #4: White" (Magic Eye Records, 1997)
• "Diggin Holes" b/w "Babys Clean Conscience" (Sub Pop Records, 2002)
• Sharpen Your Teeth (Sub Pop Records, 2002)
• 180 Degrees South: Conquerors of the Useless (Brushfire Records, 2010)

References[link]

External links[link]

• Sub Pop Ugly Casanova Page
• An article about Ugly Casanova
• Luckyhorse Industries - Ugly Casanova merch page
• "Who is Edgar Graham?"
• An interview with Isaac Brock
• Information regarding the band's current lineup

The Edge
Background information
Birth name	David Howell Evans
Born	(1961-08-08) 8 August 1961 (age 50) Barking, Essex, England, United Kingdom
Origin	County Dublin, Ireland
Genres	Rock, post-punk, alternative rock
Occupations	Musician, songwriter, activist
Instruments	Guitar, vocals, keyboards, piano, bass guitar
Years active	1976–present
Labels	Island, Mercury
Associated acts	U2, Passengers
Website	www.u2.com
Notable instruments
Gibson Explorer Fender Stratocaster Gibson Les Paul Fender Telecaster Gretsch Country Gentleman Gretsch White Falcon Rickenbacker 330/12

David Howell Evans (born 8 August 1961), more widely known by his stage name The Edge (or just Edge),^[1] is a musician best known as the guitarist, backing vocalist, and keyboardist of the Irish rock band U2. A member of the group since its inception, he has recorded 12 studio albums with the band and has released one solo record. As a guitarist, The Edge has crafted a minimalistic and textural style of playing. His use of a rhythmic delay effect yields a distinctive ambient, chiming sound that has become a signature of U2's music.

The Edge was born in England to a Welsh family, but was raised in Ireland after moving there as an infant. In 1976, at Mount Temple Comprehensive School, he formed U2 with his fellow students and his older brother Dik. Inspired by the ethos of punk rock and its basic arrangements, the group began to write its own material. They eventually became one of the most popular acts in popular music, with successful albums such as 1987's The Joshua Tree and 1991's Achtung Baby. Over the years, The Edge has experimented with various guitar effects and introduced influences from several genres of music into his own style, including American roots music, industrial music, and alternative rock. With U2, The Edge has also played keyboards, co-produced their 1993 record Zooropa, and occasionally contributed lyrics. The Edge met his second and current wife, Morleigh Steinberg, through her collaborations with the band.

As a member of U2 and as an individual, The Edge has campaigned for human rights and philanthropic causes. He co-founded Music Rising, a charity to support musicians affected by Hurricane Katrina. He has collaborated with U2 bandmate Bono on several projects, including songs for Roy Orbison and Tina Turner, and the soundtracks to the musical Spider-Man: Turn Off the Dark and the Royal Shakespeare Company's London stage adaptation of A Clockwork Orange. In 2011, Rolling Stone magazine placed him at number 38 on its list of "The 100 Greatest Guitarists of All Time".

Personal life[link]

The Edge at a U2 concert in Anaheim (2005)

David Howell Evans was born at the Barking Maternity Hospital,^[2] Essex, England to Welsh parents Garvin and Gwenda Evans.^[1] When he was one, his family moved to County Dublin, Ireland where he attended St Andrew's National School. He received piano and guitar lessons and often performed with his brother Dik Evans before they both answered an advertisement posted by Larry Mullen, Jr. at their school, Mount Temple Comprehensive School, seeking musicians to form a band.^[3] The band accepted both of them. This band went through several incarnations before emerging as U2 in March 1978 (Dik Evans left the band just before the name change).^[3] U2 began performing in various venues in Ireland and eventually began developing a following. Their debut album, Boy, was released in 1980.

In 1981, leading up to the October tour, Evans came very close to leaving U2 for religious reasons, but he decided to stay.^[3] During this period, he became involved with a group called Shalom Tigers, in which bandmates Bono and Larry Mullen Jr. were also involved.^[4] Shortly after deciding to remain with the band, he wrote a piece of music that later became "Sunday Bloody Sunday".^[3] The Edge married his high school girlfriend Aislinn O'Sullivan on 12 July 1983.^[5] The couple had three daughters together: Hollie in 1984, Arran in 1985 and Blue Angel in 1989.^[4] The couple separated in 1990, but were unable to get officially divorced because of Irish laws regarding marriage annulment; divorce was legalised in 1995 and the couple were legally divorced in 1996.^[4]

In 1993, The Edge began dating Morleigh Steinberg, a professional dancer and choreographer employed by the band as a belly dancer during the Zoo TV Tour. They had a daughter, Sian (born 1997), and a son, Levi (born 25 October 1999),^[4] before marrying on 22 June 2002.^[4] He appeared in the 2009 music documentary film It Might Get Loud.^[6] The Edge has been criticized for his efforts to build five luxury mansions on a 156 acre plot of land in Malibu, California.^[7] The California Coastal Commission voted 8-4 against the plans, with the project described by the commission's executive director, Peter Douglas, as "In 38 years...one of the three worst projects that I've seen in terms of environmental devastation...It's a contradiction in terms – you can't be serious about being an environmentalist and pick this location."^[7] The Santa Monica Mountains Conservancy agreed to remain neutral on the issue following a $1 million donation from The Edge and a commitment from The Edge to designate 100 acres of the land as open space for public footpaths.^[7]

Music style[link]

Guitar playing[link]

As a guitar player, The Edge has a sound typified by a low-key playing style, a chiming, shimmering sound (thanks in part to the sound of VOX AC-30s) that he achieves with extensive use of delay effects and reverb. The feedback delay is often set to a dotted eighth note (3/16 of a measure), and the feedback gain is adjusted until a note played repeats two or three times.^{[citation needed]}

On 1987's The Joshua Tree, The Edge often contributes just a few simple lead lines given depth and richness by an ever-present delay. For example, the introduction to "Where the Streets Have No Name" is simply a repeated six-note arpeggio, broadened by a modulated delay effect. The Edge has said that he views musical notes as "expensive", in that he prefers to play as few notes as possible. He said in 1982 of his style,

"I like a nice ringing sound on guitar, and most of my chords I find two strings and make them ring the same note, so it's almost like a 12-string sound. So for E I might play a B, E, E and B and make it ring. It works very well with the Gibson Explorer. It's funny because the bass end of the Explorer was so awful that I used to stay away from the low strings, and a lot of the chords I played were very trebly, on the first four, or even three strings. I discovered that through using this one area of the fretboard I was developing a very stylized way of doing something that someone else would play in a normal way."^[9]

Many different influences have shaped The Edge's guitar technique.^{[citation needed]} His first guitar was an old acoustic guitar that his mother bought him at a local flea market for only a few pounds; he was nine at the time. He and his brother Dik Evans both experimented with this instrument.^[9] He said in 1982 of this early experimentation, "I suppose the first link in the chain was a visit to the local jumble sale where I purchased a guitar for a pound. That was my first instrument. It was an acoustic guitar and me and my elder brother Dik both played it, plonking away, all very rudimentary stuff, open chords and all that."^[9] The Edge has stated that many of his guitar parts are based around guitar effects. This is especially true from the Achtung Baby era onwards, although much of the band's 1980s material made heavy use of echos.

Vocals[link]

The Edge in June 2005

The Edge also supplies the backing vocals for U2. U2's 1983 live album and video release, Under a Blood Red Sky and Live at Red Rocks: Under a Blood Red Sky are good reference points for his singing (as are the live DVDs from the Elevation Tour, U2 Go Home: Live from Slane Castle and Elevation 2001: Live from Boston). For example, he sings the chorus to "Sunday Bloody Sunday" (Bono harmonizes on the final 'Sunday'). U2 used this tradeoff technique later in "Bullet the Blue Sky" as well. His backing vocals are sometimes in the form of a repeated cry; examples of songs that use this approach include "Beautiful Day", "New Year's Day" and "Stay (Faraway, So Close!)". Another technique he uses in his backing vocals is the falsetto, in songs such as "Stuck in a Moment You Can't Get Out Of", "Sometimes You Can't Make It on Your Own", "A Man and a Woman", "The Wanderer", live versions of "The Fly", and "Window in the Skies".

The Edge sings the lead vocal on "Van Diemen's Land" and "Numb", the first half of the song "Seconds", dual vocals with Bono in "Discotheque", and the bridge in the song "Miracle Drug".^[4] He also sings the occasional lead vocal in live renditions of other songs (such as "Sunday Bloody Sunday" during the PopMart Tour and "Party Girl" during the Rotterdam Zoo TV show when it was Bono's birthday).^[10] He also plays a solo acoustic version of the song "Love is Blindness" that is featured in the documentary film From the Sky Down.

Other instruments[link]