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{{Short description|Frozen water: the solid state of water}}
{{good article}}
{{About|water ice|the broader concept of "ices" as used in the planetary sciences|Volatile (astrogeology)|the American law enforcement agency|United States Immigration and Customs Enforcement|other uses}}
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{{Use dmy dates|date=June 2025}}
{{Infobox material
| name = Ice
| image = Ice Block, Canal Park, Duluth (32752478892).jpg
| image_size = 
| alt = A picture of ice
| caption = An ice block
| type = 
| density = 0.9167<ref name=CRC/>–0.9168<ref name=Voitkovskii/> g/cm<sup>3</sup>

| abbe_number =

| refractive_index = 1.309
| chemical formula = {{chem2|H2O}}
| youngs_modulus = 3400 to 37,500 [[Kilogram-force|kg-force]]/cm<sup>3</sup><ref name=Voitkovskii>{{Citation
 |last        = Voitkovskii
 |first       = K. F.
 |title       = Translation of: "The mechanical properties of ice" ("Mekhanicheskie svoistva l'da")
 |publisher   = Academy of Sciences (USSR)
 |id={{DTIC|AD0662716}}
}}</ref>
| tensile_strength = 5 to 18&nbsp;kg-force/cm<sup>2</sup><ref name=Voitkovskii/>
| elongation = 
| compressive_strength = 24 to 60&nbsp;kg-force/cm<sup>2</sup><ref name=Voitkovskii/>
| poissons_ratio = {{val|0.36|0.13}}<ref name=Voitkovskii/>
| thermal_conductivity = 0.0053(1 + 0.0015 ''θ'') cal/(cm s K), ''θ'' = temperature in °C<ref name=Voitkovskii/>
| thermal_diffusivity = 
| linear_expansion = {{val|5.5|e=-5}}<ref name=Voitkovskii/>
| specific_heat = 0.5057 − 0.001863 ''θ'' cal/(g K), ''θ'' = absolute value of temperature in °C<ref name=Voitkovskii/>
| specific_heat_note = 
| dielectric_constant = ~95<ref>{{cite journal |doi=10.3189/S0022143000018840|title=Dielectric Properties of Ice and Snow–a Review |year=1965 |last1=Evans |first1=S. |journal=Journal of Glaciology |volume=5 |issue=42 |pages=773–792 |s2cid=227325642 |doi-access=free }}</ref>
| footnotes = The properties of ice vary substantially with temperature, purity and other factors.
}}

'''Ice''' is [[water]] that is [[freezing|frozen]] into a [[solid]] state, typically forming at or below temperatures of 0 °[[Celsius|C]], 32 °[[Fahrenheit|F]], or 273.15 [[Kelvin|K]]. It occurs naturally on [[Earth]], on other planets<!-- including those as close to the Sun as [[Mercury (planet)|Mercury]] -->, in [[Oort cloud]] objects, and as [[interstellar ice]]. As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered to be a [[mineral]]. Depending on the presence of [[Impurity|impurities]] such as particles of [[soil]] or bubbles of [[air]], it can appear transparent or a more or less [[Opacity (optics)|opaque]] bluish-white color. 

Virtually all of the ice on Earth is of a [[Hexagonal crystal system|hexagonal]] [[Crystal structure|crystalline structure]] denoted as ''ice I<sub>h</sub>'' (spoken as "ice one h"). Depending on temperature and pressure, at least nineteen [[phases of ice|phases]] ([[Sphere packing|packing geometries]]) can exist. The most common [[phase transition]] to ice I<sub>h</sub> occurs when liquid water is cooled below {{val|0|ul=°C}} ({{val|273.15|ul=K}}, {{val|32|ul=°F}}) at [[standard atmospheric pressure]]. When water is cooled rapidly ([[quenching]]), up to three types of amorphous ice can form. Interstellar ice is overwhelmingly low-density amorphous ice (LDA), which likely makes LDA ice the most abundant type in the universe. When cooled slowly, correlated proton tunneling occurs below {{val|-253.15|ul=°C}} ({{val|20|ul=K}}, {{val|-423.67|ul=°F}}) giving rise to [[macroscopic quantum phenomena]]. 
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Ice is abundant on the Earth's surface, particularly [[Polar ice cap|in the polar regions]] and above the [[snow line]], where it can aggregate from snow to form [[glaciers]] and [[ice sheet]]s. As [[snowflakes]] and [[hail]], ice is a common form of [[precipitation]], and it may also be [[Deposition (phase transition)|deposited]] directly by [[water vapor]] as [[frost]]. The transition from ice to water is melting and from ice directly to water vapor is [[Sublimation (phase transition)|sublimation]]. These processes play a key role in Earth's [[water cycle]] and [[climate]]. In the recent decades, ice volume on Earth has been decreasing due to [[climate change]]. The largest declines have occurred in the [[Arctic]] and in the mountains located outside of the polar regions. The loss of grounded ice  (as opposed to floating [[sea ice]]) is the primary contributor to [[sea level rise]].

Humans have been using ice for various purposes for thousands of years. Some historic structures designed to hold ice to provide cooling are over 2,000 years old. Before the invention of [[refrigeration]] technology, the only way to safely store food without modifying it through [[preservative]]s was to use ice. Sufficiently solid surface ice makes [[waterway]]s accessible to land transport during winter, and dedicated [[ice road]]s may be maintained. Ice also plays a major role in [[winter sport]]s.

==Physical properties==
{{Further|Water (properties)#Density of water and ice}}
[[File:Ice Ih Crystal Lattice.png|thumb|The three-dimensional crystal structure of H{{sub|2}}O ice I<sub>h</sub> (c) is composed of bases of H{{sub|2}}O ice molecules (b) located on lattice points within the two-dimensional hexagonal space lattice (a).<ref name="Physics of Ice">Physics of Ice, V. F. Petrenko, R. W. Whitworth, Oxford University Press, 1999, {{ISBN|9780198518945}}</ref><ref>{{cite journal|doi = 10.1063/1.1749327|title = A Theory of Water and Ionic Solution, with Particular Reference to Hydrogen and Hydroxyl Ions|year = 1933|author1=Bernal, J. D. |author2=Fowler, R. H. |journal = The Journal of Chemical Physics|volume = 1|issue = 8|page = 515|bibcode = 1933JChPh...1..515B }}</ref>]]

Ice possesses a regular [[crystalline]] structure based on the [[molecule]] of water, which consists of a single [[oxygen]] atom [[covalently]] bonded to two [[hydrogen atom]]s, or H–O–H. However, many of the physical properties of water and ice are controlled by the formation of [[hydrogen bond]]s 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.<ref name=bjerrum>{{cite journal|last=Bjerrum|first=N|title=Structure and Properties of Ice|journal=Science|date=11 April 1952|volume=115|issue=2989|pages=385–390|doi=10.1126/science.115.2989.385|pmid=17741864|bibcode = 1952Sci...115..385B }}</ref>

An unusual property of water is that its solid form—ice frozen at [[atmospheric pressure]]—is approximately 8.3% less dense than its liquid form; this is equivalent to a volumetric expansion of 9%. The [[density]] of ice is 0.9167<ref name=CRC>{{cite book |chapter=Properties of Ice and Supercooled Water |first=Allan H. |last=Harvey |editor1= Haynes, William M. |editor2 = Lide, David R. |editor3=Bruno, Thomas J. |title = CRC Handbook of Chemistry and Physics |edition = 97th |location = Boca Raton, FL |publisher = CRC Press |year = 2017 |isbn = 978-1-4987-5429-3}}</ref>–0.9168<ref name=Voitkovskii/>&nbsp;g/cm<sup>3</sup> at 0&nbsp;°C and standard atmospheric pressure (101,325&nbsp;Pa), whereas water has a density of 0.9998<ref name=CRC/>–0.999863<ref name=Voitkovskii/>&nbsp;g/cm<sup>3</sup> at the same temperature and pressure. Liquid water is densest, essentially 1.00&nbsp;g/cm<sup>3</sup>, at 4&nbsp;°C and begins to lose its density as the water molecules begin to form the [[Hexagonal (crystal system)|hexagonal]] [[crystal]]s of [[ice crystals|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. The density of ice increases slightly with decreasing temperature and has a value of 0.9340&nbsp;g/cm<sup>3</sup> at −180&nbsp;°C (93&nbsp;K).<ref>{{RubberBible86th}}</ref>

When water freezes, it increases in volume (about 9% for fresh water).<ref name="LibreTexts">{{Cite web |last1=Richardson |first1=Eliza |title=Ice, Water, and Vapor |url=https://geo.libretexts.org/Bookshelves/Oceanography/Essentials_of_Oceanography_(Richardson)/03%3A_From_Rock_to_Salt/3.02%3A_Ice_Water_and_Vapor |website=LibreTexts Geosciences |date=20 June 2021 |language=en |access-date=26 April 2024 }}</ref> The effect of expansion during freezing can be dramatic, and ice expansion is a basic cause of [[freeze-thaw]] weathering of rock in nature and damage to building foundations and roadways from [[frost heaving]]. 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.<ref name="Akyurt2002">{{cite journal |last1=Akyurt |first1=M. |last2=Zaki |first2=G. |last3=Habeebullah |first3=B. |title=Freezing phenomena in ice–water systems |journal=Energy Conversion and Management |date=15 May 2002 |volume=43 |issue=14 |pages=1773–1789 |doi=10.1016/S0196-8904(01)00129-7 |bibcode=2002ECM....43.1773A }}</ref>

Because ice is less dense than liquid water, it floats, and this prevents bottom-up freezing of the bodies of water. Instead, a sheltered environment for animal and plant life is formed beneath the floating ice, which protects the underside from short-term weather extremes such as [[wind chill]]. Sufficiently thin floating ice allows light to pass through, supporting the [[photosynthesis]] of bacterial and algal colonies.<ref>{{cite web|url=http://www.haydenplanetarium.org/tyson/read/1998/05/01/water-water|title=Water, Water|author=Tyson, Neil deGrasse|publisher=haydenplanetarium.org|url-status=live|archive-url=https://web.archive.org/web/20110726095920/http://www.haydenplanetarium.org/tyson/read/1998/05/01/water-water|archive-date=26 July 2011}}</ref> When sea water freezes, the ice is riddled with brine-filled channels which sustain [[Sympagic ecology|sympagic organisms]] such as bacteria, algae, [[copepod]]s and [[annelid]]s. In turn, they provide food for animals such as [[krill]] and specialized fish like the [[bald notothen]], fed upon in turn by larger animals such as [[emperor penguins]] and [[minke whales]].<ref>[http://www.acecrc.sipex.aq/access/page/?page=d664da82-b244-102a-8ea7-0019b9ea7c60 Sea Ice Ecology] {{webarchive|url=https://web.archive.org/web/20120321204557/http://www.acecrc.sipex.aq/access/page/?page=d664da82-b244-102a-8ea7-0019b9ea7c60 |date=21 March 2012 }}. Acecrc.sipex.aq. Retrieved 30 October 2011.</ref>

[[File:Frozen Wappinger Creek.JPG|thumb|Frozen waterfall in southeast [[New York (state)|New York]]]]

When ice melts, it absorbs as much [[Heat|energy]] as it would take to heat an equivalent mass of water by {{cvt|80|C|F}}.<ref name="ESA" /> During the melting process, the temperature remains constant at {{cvt|0|C|F}}. 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]]''.<ref name="ESA">{{Cite web |title=Ice – a special substance |date=16 April 2013 |url=https://www.esa.int/SPECIALS/Eduspace_Global_EN/SEMHE7TWLUG_0.html |publisher=[[European Space Agency]] |language=en |access-date=26 April 2024 }}</ref><ref name="LibreTexts" />

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.<ref name=color>{{cite book|author1=Lynch, David K. |author2=Livingston, William Charles |title=Color and light in nature|url=https://books.google.com/books?id=4Abp5FdhskAC&pg=PA161|year=2001|publisher=Cambridge University Press|isbn=978-0-521-77504-5|pages=161–}}</ref> 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, [[iceberg]]s containing impurities (e.g., sediments, algae, air bubbles) can appear brown, grey or green.<ref name=color/>

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]] of 2 or less, but the hardness increases to about 4 at a temperature of {{convert|-44|C||sp=us}} and to 6 at a temperature of {{convert|-78.5|C||sp=us}}, the vaporization point of solid [[carbon dioxide]] (dry ice).<ref>{{cite journal |last1=Walters |first1=S. Max |title=Hardness of Ice at Low Temperatures |journal=Polar Record |date=January 1946 |volume=4 |issue=31 |pages=344–345 |doi=10.1017/S003224740004239X|s2cid=250049037 |doi-access=free |bibcode=1946PoRec...4..344. }}</ref>

==={{anchor|Phases}}Phases===
{{Main|Phases of ice}}

[[File:Phase diagram of water.svg|thumb|[[Semi-log plot|Log-lin]] pressure-temperature [[phase diagram]] of water. The [[Roman numeral]]s correspond to some ice phases listed below.]]
[[File:3D representation of several phases of water.jpg|thumb|An alternative formulation of the phase diagram for certain ices and other phases of water<ref>{{cite journal |last1=David |first1=Carl |title=Verwiebe's '3-D' Ice phase diagram reworked |journal=Chemistry Education Materials |date=8 August 2016 |url=https://opencommons.uconn.edu/chem_educ/94/ }}</ref>]]

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 {{convert|1|atm|MPa|abbr=on}}, water freezes at a temperature ''below'' {{cvt|0|C|F}}. Ice, water, and [[water vapour]] can coexist at the [[triple point]], which is exactly {{cvt|273.16|K|C}} at a pressure of 611.657&nbsp;[[Pascal (unit)|Pa]].<ref>{{cite journal |last1=Wagner |first1=Wolfgang |last2=Saul |first2=A. |last3=Pruss |first3=A. |title=International Equations for the Pressure Along the Melting and Along the Sublimation Curve of Ordinary Water Substance |journal=Journal of Physical and Chemical Reference Data |date=May 1994 |volume=23 |issue=3 |pages=515–527 |doi=10.1063/1.555947 |bibcode=1994JPCRD..23..515W }}</ref><ref>{{cite journal|doi=10.1256/qj.04.94 | volume=131 | issue=608 | title=Review of the vapour pressures of ice and supercooled water for atmospheric applications | year=2005 | journal=Quarterly Journal of the Royal Meteorological Society | pages=1539–1565 | last1 = Murphy | first1 = D. M.| bibcode=2005QJRMS.131.1539M | s2cid=122365938 | url=https://zenodo.org/record/1236243 | doi-access=free }}</ref> The [[kelvin]] was defined as {{sfrac|1|273.16}} of the difference between this triple point and [[absolute zero]],<ref>{{cite web|url=http://www1.bipm.org/en/si/base_units/|title=SI base units|publisher=Bureau International des Poids et Mesures|access-date=31 August 2012|url-status=live|archive-url=https://web.archive.org/web/20120716202131/http://www.bipm.org/en/si/base_units/|archive-date=16 July 2012}}</ref> though this definition [[2019 revision of the SI|changed]] in May 2019.<ref>{{cite web |url=https://www.bipm.org/utils/common/pdf/SI-statement.pdf |title=Information for users about the proposed revision of the SI |publisher=Bureau International des Poids et Mesures |access-date=6 January 2019 |archive-date=21 January 2018 |archive-url=https://web.archive.org/web/20180121160000/https://www.bipm.org/utils/common/pdf/SI-statement.pdf }}</ref> Unlike most other solids, ice is difficult to [[Superheating|superheat]]. In an experiment, ice at −3&nbsp;°C was superheated to about 17&nbsp;°C for about 250 [[picosecond]]s.<ref>{{cite journal|journal=Nature|volume=439|pages=183–186|year=2006| doi=10.1038/nature04415|pmid=16407948|title=Ultrafast superheating and melting of bulk ice|bibcode=2006Natur.439..183I|last1=Iglev|first1=H.|last2=Schmeisser|first2=M.|last3=Simeonidis|first3=K.|last4=Thaller|first4=A.|last5=Laubereau|first5=A.|issue=7073|s2cid=4404036}}</ref>

Subjected to higher pressures and varying temperatures, ice can form in nineteen separate known crystalline phases at various densities, along with hypothetical proposed phases of ice that have not been observed.<ref name="Metcalfe-2021">{{cite news|last1=Metcalfe|first1=Tom|date=9 March 2021|title=Exotic crystals of 'ice 19' discovered|language=en|work=Live Science|url=https://www.livescience.com/exotic-ice-19-discovered.html}}</ref> With care, at least fifteen of these phases (one of the known exceptions being ice X) can be recovered at ambient pressure and low temperature in [[metastable]] form.<ref>{{cite journal|last=La Placa|first=S. J.|author2=Hamilton, W. C.|author3=Kamb, B.|author4=Prakash, A.|year=1972|title=On a nearly proton ordered structure for ice IX|journal=Journal of Chemical Physics|volume=58|issue=2|pages=567–580|doi=10.1063/1.1679238|bibcode = 1973JChPh..58..567L }}</ref><ref>{{cite journal|last=Klotz|first=S.|author2=Besson, J. M.|author3=Hamel, G.|author4=Nelmes, R. J.|author5=Loveday, J. S.|author6=Marshall, W. G.|year=1999|title=Metastable ice VII at low temperature and ambient pressure|journal=Nature|volume=398|issue=6729|pages=681–684|doi=10.1038/19480|bibcode = 1999Natur.398..681K |s2cid=4382067}}</ref> The types are differentiated by their crystalline structure, proton ordering,<ref>{{cite web|url=https://www.uwgb.edu/dutchs/Petrology/Ice%20Structure.HTM|title=Ice Structure|last=Dutch|first=Stephen|publisher=University of Wisconsin Green Bay|access-date=12 July 2017|archive-url=https://web.archive.org/web/20161016143124/http://www.uwgb.edu/dutchs/petrology/Ice%20Structure.HTM|archive-date=16 October 2016}}</ref> and density. There are also two metastable phases of ice under pressure, both fully hydrogen-disordered; these are Ice IV and Ice XII. Ice XII was discovered in 1996. In 2006, Ice XIII and Ice XIV were discovered.<ref>{{cite journal |last1=Salzmann |first1=Christoph G. |last2=Radaelli |first2=Paolo G. |last3=Hallbrucker |first3=Andreas |last4=Mayer |first4=Erwin |last5=Finney |first5=John L. |title=The Preparation and Structures of Hydrogen Ordered Phases of Ice |journal=Science |date=24 March 2006 |volume=311 |issue=5768 |pages=1758–1761 |doi=10.1126/science.1123896 |pmid=16556840 |bibcode=2006Sci...311.1758S |s2cid=44522271 }}</ref> Ices XI, XIII, and XIV are hydrogen-ordered forms of ices I{{sub|h}}, V, and XII respectively. In 2009, ice XV was found at extremely high pressures and −143&nbsp;°C.<ref>{{cite magazine|url=http://www.sciencenews.org/view/generic/id/47258/title/A_very_special_snowball|title=A Very Special Snowball|author=Sanders, Laura|magazine=Science News|date=11 September 2009|access-date=11 September 2009|url-status=live|archive-url=https://web.archive.org/web/20090914174027/http://www.sciencenews.org/view/generic/id/47258/title/A_very_special_snowball|archive-date=14 September 2009}}</ref> At even higher pressures, ice is predicted to become a [[metal]]; this has been variously estimated to occur at 1.55&nbsp;TPa<ref>{{cite journal |last1=Militzer |first1=Burkhard |last2=Wilson |first2=Hugh F. |title=New Phases of Water Ice Predicted at Megabar Pressures |journal=Physical Review Letters |date=2 November 2010 |volume=105 |issue=19 |article-number=195701 |doi=10.1103/PhysRevLett.105.195701 |pmid=21231184 |arxiv=1009.4722 |bibcode=2010PhRvL.105s5701M |s2cid=15761164 }}</ref> or 5.62&nbsp;TPa.<ref>{{cite journal|author=MacMahon, J. M.|title=Ground-State Structures of Ice at High-Pressures|doi=10.1103/PhysRevB.84.220104|arxiv=1106.1941|bibcode=2011PhRvB..84v0104M|year=1970|journal=Physical Review B|volume=84|issue=22|article-number=220104|s2cid=117870442}}</ref>

As well as crystalline forms, solid water can exist in amorphous states as [[amorphous solid water]] (ASW) of varying densities. In outer space, hexagonal crystalline ice is present in the [[ice volcano]]es,<ref>{{cite news|url=https://www.nytimes.com/2004/12/09/science/09ice.html|title=Astronomers Contemplate Icy Volcanoes in Far Places|author=Chang, Kenneth|work=The New York Times|date=9 December 2004|access-date=30 July 2012|url-status=live|archive-url=https://web.archive.org/web/20150509123243/http://www.nytimes.com/2004/12/09/science/09ice.html|archive-date=9 May 2015}}</ref> but is extremely rare otherwise. Even icy moons like [[Ganymede (moon)|Ganymede]] are expected to mainly consist of other crystalline forms of ice.<ref>{{cite journal |url=http://www.jhuapl.edu/techdigest/TD/td2602/Prockter.pdf |title=Ice in the Solar System |author=Prockter, Louise M. |journal=Johns Hopkins APL Technical Digest |volume=26 |issue=2 |year=2005 |page=175 |archive-url=https://web.archive.org/web/20150319063545/http://www.jhuapl.edu/techdigest/TD/td2602/Prockter.pdf |archive-date=19 March 2015 |access-date=21 December 2013 }}</ref><ref name=showman1997>{{Cite journal | doi = 10.1006/icar.1997.5778| title = Coupled Orbital and Thermal Evolution of Ganymede| journal = Icarus| volume = 129| issue = 2| pages = 367–383| year = 1997| last1 = Showman | first1 = A. | bibcode = 1997Icar..129..367S| url = http://www.lpl.arizona.edu/~showman/publications/showman-etal-1997.pdf}}</ref> Water in the [[interstellar medium]] is dominated by amorphous ice, making it likely the most common form of water in the universe.<ref name="stanley">{{cite journal|last1=Debennetti|first1=Pablo G. |last2=Stanley |first2=H. Eugene |year=2003 |title=Supercooled and Glassy Water |journal=Physics Today |volume=56 |issue=6 |pages=40–46 |bibcode=2003PhT....56f..40D|doi=10.1063/1.1595053 |url=http://polymer.bu.edu/hes/articles/ds03.pdf |access-date=19 September 2012 }}</ref>  Low-density ASW (LDA), also known as hyperquenched glassy water, may be responsible for [[noctilucent clouds]] on Earth and is usually formed by [[vapor deposition|deposition]] of water vapor in cold or vacuum conditions.<ref>{{cite journal |last1=Lübken |first1=F.-J. |last2=Lautenbach |first2=J. |last3=Höffner |first3=J. |last4=Rapp |first4=M. |last5=Zecha |first5=M. |title=First continuous temperature measurements within polar mesosphere summer echoes |journal=Journal of Atmospheric and Solar-Terrestrial Physics |date=March 2009 |volume=71 |issue=3–4 |pages=453–463 |doi=10.1016/j.jastp.2008.06.001|bibcode=2009JASTP..71..453L }}</ref> High-density ASW (HDA) is formed by compression of ordinary ice I{{sub|h}} or LDA at GPa pressures. Very-high-density ASW (VHDA) is HDA slightly warmed to 160&nbsp;K under 1–2&nbsp;GPa pressures.<ref>{{cite journal|doi=10.1039/b108676f|title=A second distinct structural "state" of high-density amorphous ice at 77 K and 1 bar|year=2001|author1-link=Thomas Loerting|last1=Loerting|first1=Thomas|last2=Salzmann|first2=Christoph|last3=Kohl|first3=Ingrid|last4=Mayer|first4=Erwin|last5=Hallbrucker|first5=Andreas|s2cid=59485355|journal=Physical Chemistry Chemical Physics |volume=3 |pages=5355–5357 |issue=24 |bibcode=2001PCCP....3.5355L }}</ref>

Ice from a theorized superionic water may possess two crystalline structures. At pressures in excess of {{convert|500000|bar|psi}} such ''superionic ice'' would take on a [[body-centered cubic]] structure. However, at pressures in excess of {{convert|1000000|bar|psi}} the structure may shift to a more stable [[face-centered cubic]] lattice. It is speculated that superionic ice could compose the interior of ice giants such as Uranus and Neptune.<ref name=Phys.org-2013-04-25>{{cite news |website=Phys.org |url=http://phys.org/news/2013-04-phase-dominate-interiors-uranus-neptune.html |title=New phase of water could dominate the interiors of Uranus and Neptune |first=Lisa |last=Zyga |date=25 April 2013}}</ref>

===Friction properties===
[[File:2011 Figure Skating WC Takahiko Kozuka.jpg|thumb|[[Takahiko Kozuka]] figure skating – an act which is only possible due to ice's low frictional properties]]
Ice is "[[slipperiness|slippery]]" because it has a low coefficient of friction. This subject was first scientifically investigated in the 19th century. The preferred explanation at the time was "[[Pressure melting point|pressure melting]]" – i.e. the blade of an ice skate, upon exerting pressure on the ice, would melt a thin layer, providing sufficient lubrication for the blade to glide across the ice.<ref name="Rosenberg-2005" /> Yet, research in 1939 by Frank P. Bowden and T. P. Hughes found that skaters would experience a lot more friction than they actually do if it were the only explanation. Further, the optimum temperature for figure skating is {{convert|-5.5|C|F K|0}} and {{convert|−9|C|F K|0}} for ice hockey; yet, according to pressure melting theory, skating below {{convert|−4|C|F K|0}} would be outright impossible.<ref name="Chang2006" /> Instead, Bowden and Hughes argued that heating and melting of the ice layer is caused by friction. However, this theory does not sufficiently explain why ice is slippery when standing still even at below-zero temperatures.<ref name="Rosenberg-2005">{{cite journal |last1=Rosenberg |first1=Robert |title=Why Is Ice Slippery? |journal=Physics Today |date=2005 |volume=58 |issue=12 |pages=50–54 |doi=10.1063/1.2169444 |bibcode=2005PhT....58l..50R |doi-access=free }}</ref>

Subsequent research 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]] for ice using [[atomic force microscopy]].<ref name=Chang2006>{{cite news |first=Kenneth |last=Chang |title=Explaining Ice: The Answers Are Slippery |work=[[The New York Times]] |date=21 February 2006 |access-date=8 April 2009 |url=https://www.nytimes.com/2006/02/21/science/21ice.html?pagewanted=all |url-status=live |archive-url=https://web.archive.org/web/20081211055112/http://www.nytimes.com/2006/02/21/science/21ice.html?pagewanted=all |archive-date=11 December 2008 }}</ref> Thus, the mechanism controlling the frictional properties of ice is still an active area of scientific study.<ref>{{cite journal |last1=Canale |first1=L. |title=Nanorheology of Interfacial Water during Ice Gliding |journal=[[Physical Review X]] |date=4 September 2019 |volume=9 |issue=4 |article-number=041025 |doi=10.1103/PhysRevX.9.041025 |arxiv=1907.01316 |bibcode=2019PhRvX...9d1025C |doi-access=free }}</ref> A comprehensive theory of ice friction must take into account all of the aforementioned mechanisms to estimate friction coefficient of ice against various materials as a function of temperature and sliding speed. Research in 2014 suggests that frictional heating is the most important process under most typical conditions.<ref name=Makkonen2014>{{cite journal|last1=Makkonen|first1=Lasse|last2=Tikanmäki|first2=Maria|title=Modeling the friction of ice|journal=Cold Regions Science and Technology|date=June 2014|volume=102|pages=84–93|doi=10.1016/j.coldregions.2014.03.002|bibcode=2014CRST..102...84M }}</ref>

==Natural formation==
[[File:Tsu Lake Ice Circle.jpg|thumb|Frozen landscape in the [[Northwest Territories]] of [[Canada]]. A large ice circle can be clearly seen floating on water.<ref>{{Cite journal |last=Dorbolo |first=S. |date=2016 |title=Rotation of melting ice disks due to melt fluid flow |url=https://journals.aps.org/pre/abstract/10.1103/PhysRevE.93.033112 |journal=Physical Review E |volume=93 |issue=3 |article-number=033112 |doi=10.1103/PhysRevE.93.033112|pmid=27078452 |bibcode=2016PhRvE..93c3112D |arxiv=1510.06505 }}</ref><ref>{{Cite journal |last1=Stepanova |first1=E. V. |last2=Chaplina |first2=T. O. |date=December 2019 |title=Vortex Flow Formation by a Melting Ice Block |url=http://link.springer.com/10.1134/S0015462819070140 |journal=Fluid Dynamics |language=en |volume=54 |issue=7 |pages=1002–1008 |doi=10.1134/S0015462819070140 |bibcode=2019FlDy...54.1002S |issn=0015-4628|url-access=subscription }}</ref>]] 
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 [[snowpack]]s are an important storage mechanism for fresh water; over time, they may sublimate or melt. [[Snowmelt]] is an important source of seasonal fresh water.<ref name="HKH2019Cryo" /><ref name="HKH2019Water" /> The [[World Meteorological Organization]] defines several kinds of ice depending on origin, size, shape, influence and so on.<ref name=wmo>[http://www.aari.nw.ru/gdsidb/XML/volume1.php?lang1=0&lang2=1&arrange=0&self=0 "WMO Sea-Ice Nomenclature"] {{webarchive |url=https://web.archive.org/web/20130605124444/http://www.aari.nw.ru/gdsidb/XML/volume1.php?lang1=0&lang2=1&arrange=0&self=0 |date=5 June 2013 }} ([http://www.aari.nw.ru/gdsidb/XML/wmo_259.php Multi-language] {{webarchive |url=https://web.archive.org/web/20120414141500/http://www.aari.nw.ru/gdsidb/XML/wmo_259.php |date=14 April 2012 }}) ''World Meteorological Organization'' / ''[[Arctic and Antarctic Research Institute]]''. Retrieved 8 April 2012.</ref> [[Clathrate hydrate]]s are forms of ice that contain gas molecules trapped within their crystal lattice.<ref>{{Cite journal|doi=10.1021/ie00019a001|title=Clathrate hydrates|year=1993 |last1=Englezos |first1=Peter|journal=Industrial & Engineering Chemistry Research |volume=32|issue=7|pages=1251–1274}}</ref><ref>{{cite web |publisher=U.S. Geological Survey |url=https://woodshole.er.usgs.gov/project-pages/hydrates/what.html |date=31 August 2009 |access-date=28 December 2014 |title=Gas Hydrate: What is it? |archive-url=https://web.archive.org/web/20120614141539/http://woodshole.er.usgs.gov/project-pages/hydrates/what.html |archive-date=June 14, 2012}}</ref>

=== In the oceans ===
{{main|Sea ice}}
Ice that is found at sea may be in the form of [[drift ice]] floating in the water, [[fast ice]] fixed to a shoreline or [[anchor ice]] if attached to the seafloor.<ref>{{cite report |date=2014 |title=WMO Sea-ice Nomenclature |url=https://library.wmo.int/records/item/41953-wmo-sea-ice-nomenclature |publisher=Secretariat of the World Meteorological Organization }}</ref> Ice which [[Ice calving|calves]] (breaks off) from an [[ice shelf]] or a coastal glacier may become an iceberg.<ref>{{cite journal | last1 = Benn | first1 = D. | last2 = Warren | first2 = C. | last3 = Mottram | first3 = R. | year = 2007 | title = Calving processes and the dynamics of calving glaciers | url = http://stuff.mit.edu/~heimbach/papers_glaciology/earthscirev_benn_etal_2007_calving.pdf | journal = Earth-Science Reviews | volume = 82 | issue = 3–4| pages = 143–179 | doi=10.1016/j.earscirev.2007.02.002| bibcode = 2007ESRv...82..143B }}</ref> The aftermath of calving events produces a loose mixture of snow and ice known as [[ice mélange]].<ref>{{Cite journal|last=Robel|first=Alexander A.|date=2017-03-01|title=Thinning sea ice weakens buttressing force of iceberg mélange and promotes calving|journal=Nature Communications|language=en|volume=8|article-number=14596|doi=10.1038/ncomms14596|pmid=28248285|pmc=5339875|bibcode=2017NatCo...814596R |issn=2041-1723}}</ref> 

Sea ice forms in several stages. At first, small, millimeter-scale crystals accumulate on the water surface in what is known as [[frazil ice]]. As they become somewhat larger and more consistent in shape and cover, the water surface begins to look "oily" from above, so this stage is called [[grease ice]].<ref>{{Cite journal |last1=Smedsrud |first1=Lars H. |last2=Skogseth |first2=Ragnheid |title=Field measurements of Arctic grease ice properties and processes |journal=Cold Regions Science and Technology |volume=44 |issue=3 |year=2006 |pages=171–183 |doi=10.1016/j.coldregions.2005.11.002 |bibcode=2006CRST...44..171S }}</ref> Then, ice continues to clump together, and solidify into flat cohesive pieces known as [[ice floe]]s. Ice floes are the basic building blocks of sea ice cover, and their horizontal size (defined as half of their [[diameter]]) varies dramatically, with the smallest measured in centimeters and the largest in hundreds of kilometers.<ref>{{cite journal |last1=Roach |first1=Lettie A. |last2=Horvat |first2=Christopher |last3=Dean |first3=Samuel M. |last4=Bitz |first4=Cecilia M. |title=An Emergent Sea Ice Floe Size Distribution in a Global Coupled Ocean-Sea Ice Model |journal=Journal of Geophysical Research: Oceans |date=6 May 2018 |volume=123 |issue=6 |pages=4322–4337 |doi=10.1029/2017JC013692 |bibcode=2018JGRC..123.4322R |doi-access=free }}</ref> An area which is over 70% ice on its surface is said to be covered by pack ice.<ref>{{cite book|first1=Qin |last1=Zhang|first2=Roger |last2=Skjetne|title=Sea Ice Image Processing with MATLAB|url=https://books.google.com/books?id=DuJLDwAAQBAJ&pg=PP43|date=13 February 2018|publisher=CRC|isbn=978-1-351-06918-2|page=43}}</ref> 

Fully formed sea ice can be forced together by currents and winds to form [[Pressure ridge (ice)|pressure ridges]] up to {{convert|12|m}} tall.<ref>{{Cite journal |last1=Leppäranta |first1=Matti |last2=Hakala |first2=Risto |date=25 April 1991 |title=The structure and strength of first-year ice ridges in the Baltic Sea |journal=Cold Regions Science and Technology |volume=20 |issue=3 |pages=295–311 |doi=10.1016/0165-232X(92)90036-T }}</ref> On the other hand, active wave activity can reduce sea ice to small, regularly shaped pieces, known as [[pancake ice]].<ref>{{Cite journal|last=Squire|first=Vernon A.|date=2020|title=Ocean Wave Interactions with Sea Ice: A Reappraisal |journal=Annual Review of Fluid Mechanics |volume=52 |issue=1 |pages=37–60 |bibcode=2020AnRFM..52...37S |doi=10.1146/annurev-fluid-010719-060301|s2cid=198458049 |issn=0066-4189 |doi-access=free}}</ref> Sometimes, wind and wave activity "polishes" sea ice to perfectly spherical pieces known as [[ice eggs]].<ref>{{Cite news |date=2019-11-07 |title='Ice eggs' cover Finland beach in rare weather event |language=en-GB |work=BBC News |url=https://www.bbc.com/news/world-europe-50338447 |access-date=2022-04-22}}</ref><ref>{{Cite web |last=geographyrealm |date=2019-11-14 |title=How Ice Balls Form |url=https://www.geographyrealm.com/how-ice-balls-form/ |access-date=2022-04-23 |website=Geography Realm |language=en-US}}</ref>

<gallery mode="packed" heights="150px">
File:GreaseIce2.jpg|Grease ice in the [[Bering Sea]]
File:Greenland East Coast 7.jpg|Loose drift ice on the east coast of Greenland
File:Jää on kulmunud pallideks (Looduse veidrused). 05.jpg|Ice eggs (diameter 5–10 cm) on Stroomi Beach, Tallinn, Estonia
File:IceNomenclature-2LightPack.jpg|Ice floes in Antarctica, 1919
File:Ridge MOSAiC.jpg|A first-year sea ice ridge in the Central Arctic, photographed by the [[MOSAiC Expedition|MOSAiC expedition]] on 4 July 2020
File:A Mélange of Ice - NASA Earth Observatory.jpg|Ice mélange on Greenland's western coast, 2012
File:Anchor ice under sea ice.JPG|Anchor ice on the seafloor at [[McMurdo Sound]], Antarctica.
</gallery>

=== On land ===
[[File:AA bedrock surface.4960.tif|thumb|[[NASA]] image of the Antarctic ice sheet]]
The largest ice formations on Earth are the two [[ice sheet]]s which almost completely cover the world's largest island, [[Greenland]], and the continent of [[Antarctica]]. These ice sheets have an average thickness of over {{convert|1|km|mi|1|abbr=on}} and have existed for millions of years.<ref name="BBC2017">{{cite web |title=How Greenland would look without its ice sheet |date=14 December 2017 |url=https://www.bbc.com/news/science-environment-42260580 |work=[[BBC News]] |access-date=7 December 2023 |archive-date=7 December 2023 |archive-url=https://web.archive.org/web/20231207201039/https://www.bbc.com/news/science-environment-42260580 |url-status=live }}</ref><ref name="Fretwell2013" /> 

Other major ice formations on land include [[ice cap]]s, [[ice field]]s, [[ice stream]]s and [[glacier]]s. In particular, the [[Hindu Kush]] region is known as the Earth's "Third Pole" due to the large number of glaciers it contains. They cover an area of around {{cvt|80,000|sqkm|sqmi}}, and have a combined volume of between 3,000 and 4,700&nbsp;km<sup>3</sup>.<ref name="HKH2019Cryo">{{Cite book |last1=Bolch |first1=Tobias |last2=Shea |first2=Joseph M. |last3=Liu |first3=Shiyin |last4=Azam |first4=Farooq M. |last5=Gao |first5=Yang |last6=Gruber |first6=Stephan |last7=Immerzeel |first7=Walter W. |last8=Kulkarni |first8=Anil |last9=Li |first9=Huilin |last10=Tahir |first10=Adnan A. |last11=Zhang |first11=Guoqing |last12=Zhang |first12=Yinsheng |display-authors=6 |title=The Hindu Kush Himalaya Assessment |date=5 January 2019 |chapter=Status and Change of the Cryosphere in the Extended Hindu Kush Himalaya Region |chapter-url=https://link.springer.com/chapter/10.1007/978-3-319-92288-1_7 |pages=209–255 |doi=10.1007/978-3-319-92288-1_7 |isbn=978-3-319-92287-4 |s2cid=134814572 }}</ref> These glaciers are nicknamed "Asian water towers", because their meltwater run-off feeds into rivers which provide water for an estimated two billion people.<ref name="HKH2019Water">{{Cite book |last1=Scott |first1=Christopher A. |last2=Zhang |first2=Fan |last3=Mukherji |first3=Aditi |last4=Immerzeel |first4=Walter |last5=Mustafa |first5=Daanish |last6=Bharati |first6=Luna |title=The Hindu Kush Himalaya Assessment |date=5 January 2019 |chapter=Water in the Hindu Kush Himalaya |chapter-url=https://link.springer.com/chapter/10.1007/978-3-319-92288-1_8 |pages=257–299 |doi=10.1007/978-3-319-92288-1_8 |isbn=978-3-319-92287-4 |s2cid=133800578 }}</ref>

[[Permafrost]] is [[soil]] or underwater [[sediment]] which continuously remains below {{cvt|0|C|F}} for two years or more.<ref>{{cite web |url=https://climate.mit.edu/explainers/permafrost |title=Permafrost |last1=McGee |first1=David |last2=Gribkoff |first2=Elizabeth |date=4 August 2022 |website=MIT Climate Portal |access-date=27 September 2023 }}</ref> The ice within permafrost is divided into four categories: pore ice, vein ice (also known as ice wedges), buried surface ice and intrasedimental ice (from the freezing of underground waters).<ref>{{Cite journal |last1=Lacelle |first1=Denis |last2=Fisher |first2=David A. |last3=Verret |first3=Marjolaine |last4=Pollard |first4=Wayne |date=17 February 2022 |title=Improved prediction of the vertical distribution of ground ice in Arctic-Antarctic permafrost sediments |journal=Communications Earth & Environment |volume=3 |issue=31 |page=31 |doi=10.1038/s43247-022-00367-z |bibcode=2022ComEE...3...31L |s2cid=246872753 |doi-access=free }}</ref> One example of ice formation in permafrost areas is [[aufeis]] – 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.<ref>{{Cite journal |last1=Huryn |first1=Alexander D. |last2=Gooseff |first2=Michael N. |last3=Hendrickson |first3=Patrick J. |last4=Briggs |first4=Martin A. |last5=Tape |first5=Ken D. |last6=Terry |first6=Neil C. |date=2020-10-13 |title=Aufeis fields as novel groundwater-dependent ecosystems in the arctic cryosphere |journal=Limnology and Oceanography |volume=66 |issue=3 |pages=607–624 |doi=10.1002/lno.11626 |s2cid=225139804 |issn=0024-3590|doi-access=free }}</ref> [[Snow line]] and [[snow field]]s are two related concepts, in that snow fields accumulate on top of and ablate away to the equilibrium point (the snow line) in an ice deposit.<ref>{{Cite book |last1=Johnson |first1=Chris |url=https://slcc.pressbooks.pub/introgeology/chapter/14-glaciers/ |title=An Introduction to Geology |last2=Affolter |first2=Matthew D. |last3=Inkenbrandt |first3=Paul |last4=Mosher |first4=Cam |date=July 1, 2017 |chapter=Chapter 14. Glaciers}}</ref>

===On rivers and streams===
[[File:Frozen rivulet in Pennsylvania.JPG|thumb|left|A small frozen [[rivulet]]]]
Ice which forms on moving water tends to be less uniform and stable than ice which forms on calm water. [[Ice jam]]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]] industrial facilities to completely shut down. An ice dam is a blockage from the movement of a glacier which may produce a [[proglacial lake]]. Heavy ice flows in rivers can also damage vessels and require the use of an [[icebreaker]] vessel to keep navigation possible.<ref>{{cite web|url=http://www.nws.noaa.gov/floodsafety/ice_jam.shtml |title=Ice Jams |publisher=NOAA |date=2013-03-13 |access-date=11 January 2014 }}</ref><ref>{{Cite news|url=https://www.popularmechanics.com/science/environment/a473/2272511/ |title=Ice Dams: Taming An Icy River|last=Staff writer|date=7 February 2006 |work=Popular Mechanics|access-date=27 March 2018 |language=en-US}}</ref>

[[Ice disc]]s are circular formations of ice floating on river water. They form within [[Eddy (fluid dynamics)|eddy current]]s, and their position results in asymmetric melting, which makes them continuously rotate at a low speed.<ref>{{Cite web |url=http://modernnotion.com/crop-circles-ice-ice-circles-form/ |title=Crop Circles in the Ice: How Do Ice Circles Form? |date=22 December 2015 |website=Modern Notion |language=en-US |access-date=16 January 2019 |archive-date=8 August 2017 |archive-url=https://web.archive.org/web/20170808193720/http://modernnotion.com/crop-circles-ice-ice-circles-form/ }}</ref><ref>{{cite journal |last1=Dorbolo |first1=S |last2=Adami |first2=N. |last3=Dubois |first3=C. |last4=Caps |first4=H. |last5=Vandewalle |first5=N. |last6=Barbois-Texier |first6=B. |title=Rotation of melting ice disks due to melt fluid flow |journal=Physical Review E |year=2016 |volume=93 |issue=3 |pages=1–5 |doi=10.1103/PhysRevE.93.033112 |pmid=27078452 |bibcode=2016PhRvE..93c3112D |hdl=2268/195696 |s2cid=118380381 |url=https://orbi.uliege.be/handle/2268/195696|arxiv=1510.06505 }}</ref>

===On lakes<span class="anchor" id="Ice on lakes"></span>===
[[File:Candle_Ice.jpg|thumb|upright=1.4|Candle ice in Lake Otelnuk, [[Quebec, Canada]]]]
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.<ref>{{cite book |last1=Petrenko |first1=Victor F. |last2=Whitworth |first2=Robert W. |year=1999 |title=Physics of Ice |location=Oxford |publisher=Oxford University Press |pages=27–29 |isbn=0-19-158134-8}}</ref><ref>{{cite book |last1=Eranti |first1=E. |last2=Lee |first2=George C. |year=1986 |title=Cold Region Structural Engineering |location=New York |publisher=McGraw-Hill |page=51 |isbn=0-07-037034-6}}</ref> 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. An [[ice shove]] 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.<ref>{{cite journal |last1=Dionne |first1=J. |title=Ice action in the lacustrine environment. A review with particular reference to subarctic Quebec, Canada |journal=Earth-Science Reviews |date=November 1979 |volume=15 |issue=3 |pages=185–212 |doi=10.1016/0012-8252(79)90082-5 |bibcode=1979ESRv...15..185D }}</ref>

[[Shelf ice]] is formed when floating pieces of ice are driven by the wind piling up on the windward shore. This kind of ice may contain large air pockets under a thin surface layer, which makes it particularly hazardous to walk across it.<ref>{{Cite news |last=Schwarz |first=Phil |date=19 February 2018 |title=Dangerous shelf ice forms along Lake Michigan |url=https://abc7chicago.com/3109973/ |work=ABC7 Chicago |access-date=2020-02-05 }}</ref> Another dangerous form of [[rotten ice]] to traverse on foot is candle ice, which develops in columns perpendicular to the surface of a lake. Because it lacks a firm horizontal structure, a person who has fallen through has nothing to hold onto to pull themselves out.<ref>{{Cite encyclopedia|title=Candle ice|encyclopedia=Glossary of Meteorology|publisher=[[American Meteorological Society]]|url=https://glossary.ametsoc.org/wiki/Candle_ice|access-date=2021-03-17|date=2012-02-20}}</ref>

=== As precipitation ===
{{Main|Precipitation}}
====Snow and freezing rain ====
{{Main|Snow|Snowflake}}
[[File:SnowflakesWilsonBentley.jpg|thumb|[[Snowflake]]s by [[Wilson Bentley]], 1902]]
Snow crystals form when tiny [[supercool]]ed cloud droplets (about 10&nbsp;[[μm]] in diameter) [[freezing|freeze]]. These droplets are able to remain liquid at temperatures lower than {{convert|-18|C|K 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 {{convert|-35|C|K F}}.<ref name=Mason>{{cite book|last = Mason |first=Basil John| publisher= Clarendon Press| isbn= 978-0-19-851603-3|year = 1971|title = Physics of Clouds|url = https://archive.org/details/physicsofclouds0000maso|url-access = registration}}</ref> 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&nbsp;– 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,<ref name=Christner2008>{{cite journal |last1=Christner |first1=Brent C. |last2=Morris |first2=Cindy E. |last3=Foreman |first3=Christine M. |last4=Cai |first4=Rongman |last5=Sands |first5=David C. |title=Ubiquity of Biological Ice Nucleators in Snowfall |journal=Science |date=29 February 2008 |volume=319 |issue=5867 |page=1214 |doi=10.1126/science.1149757 |pmid=18309078 |bibcode=2008Sci...319.1214C |citeseerx=10.1.1.714.4002 |s2cid=39398426 }}</ref> although to what extent is unclear. Artificial nuclei are used in [[cloud seeding]].<ref>{{cite encyclopedia|url=http://amsglossary.allenpress.com/glossary/search?p=1&query=cloud+seeding&submit=Search|title=Cloud seeding|encyclopedia=Glossary of Meteorology|year=2009|access-date=28 June 2009|publisher=American Meteorological Society|archive-url=https://web.archive.org/web/20120315161127/http://amsglossary.allenpress.com/glossary/search?p=1&query=cloud+seeding&submit=Search|archive-date=15 March 2012}}</ref> The droplet then grows by condensation of water vapor onto the ice surfaces.<ref>{{cite journal |last1=Pelley |first1=Janet |title=Does cloud seeding really work? |journal=Chemical and Engineering News|date=30 May 2016|volume=94 |issue=22 |pages=18–21 |url=http://cen.acs.org/articles/94/i22/Does-cloud-seeding-really-work.html |access-date=26 May 2024 |archive-date=10 November 2016 |archive-url=https://web.archive.org/web/20161110235130/http://cen.acs.org/articles/94/i22/Does-cloud-seeding-really-work.html |url-status=live}}</ref>

An [[ice storm]] is a type of winter storm characterized by [[freezing rain]], which produces a [[glaze ice|glaze]] of ice on surfaces, including roads and [[power line]]s. In the United States, a quarter of winter weather events produce glaze ice, and utilities need to be prepared to minimize damages.<ref>{{cite journal |last1=Sanders |first1=Kristopher J. |last2=Barjenbruch |first2=Brian L. |title=Analysis of Ice-to-Liquid Ratios during Freezing Rain and the Development of an Ice Accumulation Model |journal=Weather Forecasting |date=1 August 2016 |volume=31 |issue=4 |pages=1041–1060 |doi=10.1175/WAF-D-15-0118.1 |bibcode=2016WtFor..31.1041S }}</ref>

==== Hard forms ====
{{Further|Ice crystal}}
[[File:Granizo.jpg|right|thumb|A large hailstone, about {{convert|6|cm|in|abbr=on}} in diameter]]
[[Hail]] forms in storm [[cloud]]s 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 {{convert|5|mm|in}} or more.<ref name="gloss">{{cite encyclopedia|url=http://amsglossary.allenpress.com/glossary/search?id=hail1|title=Hail|year=2009|access-date=15 July 2009|encyclopedia=Glossary of Meteorology|publisher=American Meteorological Society|archive-url=https://web.archive.org/web/20100725142407/http://amsglossary.allenpress.com/glossary/search?id=hail1|archive-date=25 July 2010}}</ref> Within [[METAR]] code, GR is used to indicate larger hail, of a diameter of at least {{convert|6.4|mm|in}} and GS for smaller.<ref name="METAR">{{cite web|url=http://www.alaska.faa.gov/fai/afss/metar+taf/sametara.htm|title=SA-METAR|author=Alaska Air Flight Service Station|publisher=[[Federal Aviation Administration]] |access-date=29 August 2009|date=10 April 2007|archive-url=https://web.archive.org/web/20080501074014/http://www.alaska.faa.gov/fai/afss/metar%20taf/sametara.htm|archive-date=1 May 2008}}</ref> Stones of {{Convert|0.75|in|mm|order=flip}}, {{Convert|1.0|in|mm|order=flip}} and {{Convert|1.75|in|mm|order=flip}} are the most frequently reported hail sizes in North America.<ref>{{cite web|url=http://www.spc.noaa.gov/publications/jewell/hailslsc.pdf|title=P9.5 Evaluation of an Alberta Hail Growth Model Using Severe Hail Proximity Soundings in the United States|last1=Jewell |first1=Ryan|last2=Brimelow|first2=Julian|date=17 August 2004|access-date=15 July 2009|url-status=live|archive-url=https://web.archive.org/web/20090507044027/http://www.spc.noaa.gov/publications/jewell/hailslsc.pdf|archive-date=7 May 2009}}</ref> Hailstones can grow to {{convert|15|cm|in|0}} and weigh more than {{convert|0.5|kg|lb|1}}.<ref>{{cite web|url=http://www.photolib.noaa.gov/htmls/nssl0001.htm|title=Aggregate hailstone|author=National Severe Storms Laboratory|publisher=National Oceanic and Atmospheric Administration|date=23 April 2007|access-date=15 July 2009|url-status=live|archive-url=https://web.archive.org/web/20090810182627/http://www.photolib.noaa.gov/htmls/nssl0001.htm|archive-date=10 August 2009}}</ref> 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.<ref>{{cite journal|title=Modeling Maximum Hail Size in Alberta Thunderstorms|journal=Weather and Forecasting|last1=Brimelow |first1=Julian C. |last2=Reuter |first2=Gerhard W. |last3=Poolman |first3=Eugene R. |pages=1048–1062|volume=17|issue=5|doi=10.1175/1520-0434(2002)017<1048:MMHSIA>2.0.CO;2|bibcode = 2002WtFor..17.1048B|year=2002|doi-access=free}}</ref> 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.<ref>{{cite web|url=http://www.ucar.edu/communications/factsheets/Hail.html|title=Hail Fact Sheet|date=10 April 2000|last=Marshall |first=Jacque|access-date=15 July 2009|publisher=University Corporation for Atmospheric Research|archive-url=https://web.archive.org/web/20091015141754/http://www.ucar.edu/communications/factsheets/Hail.html|archive-date=15 October 2009}}</ref>

[[File:2013-02-23 03 59 28 Graupel (snow pellets) in Elko, Nevada.JPG|thumb|right|Soft hail, or graupel, in [[Nevada]]]]
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 {{convert|0|C|F|0}}.<ref name="gloss"/> Hail-producing clouds are often identifiable by their green coloration.<ref>{{cite web|url=http://www.abc.net.au/news/australia/qld/toowoomba/200410/s1222665.htm|archive-url=https://web.archive.org/web/20100306021712/http://www.abc.net.au/news/australia/qld/toowoomba/200410/s1222665.htm|archive-date=6 March 2010|title=Hail storms rock southern Qld|work=ABC News|publisher=Australian Broadcasting Corporation|date=19 October 2004|access-date=15 July 2009}}</ref><ref>{{cite web|url=http://australiasevereweather.com/storm_news/arc1997.htm|title=Severe Thunderstorm Images of the Month Archives|website=Australia Severe Weather|year=1997|last1=Bath|first1=Michael|last2=Degaura|first2=Jimmy|access-date=15 July 2009|url-status=live|archive-url=http://archive.wikiwix.com/cache/20110713110215/http://australiasevereweather.com/storm_news/arc1997.htm|archive-date=13 July 2011}}</ref> The growth rate is maximized at about {{convert|-13|C|F|0}}, and becomes vanishingly small much below {{convert|-30|C|F|0}} 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 {{convert|11000|ft|m}}.<ref>{{cite web|url=http://www.meted.ucar.edu/resource/soo/MesoAnalyst.htm|archive-url=https://web.archive.org/web/20030320222147/http://www.meted.ucar.edu/resource/soo/MesoAnalyst.htm|archive-date=20 March 2003|title=Meso-Analyst Severe Weather Guide|last=Wolf|first=Pete|date=16 January 2003|access-date=16 July 2009|publisher=University Corporation for Atmospheric Research}}</ref> [[Entrainment (meteorology)|Entrainment]] of dry air into strong thunderstorms over continents can increase the frequency of hail by promoting evaporative 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.<ref>{{cite book|url=https://books.google.com/books?id=UbtG3vFfNtoC&pg=PA41|title=Climate, change and risk|last1=Downing|first1=Thomas E. |last2=Olsthoorn|first2=Alexander A. |last3=Tol|first3=Richard S. J. |pages=41–43|publisher=Routledge|year=1999|isbn=978-0-415-17031-4}}</ref>

[[File:Sleet on the ground.jpg|thumb|An accumulation of ice pellets]]
Ice pellets ([[METAR]] code ''PL''<ref name="METAR"/>) are a form of precipitation consisting of small, [[translucent]] balls of ice, which are usually smaller than hailstones.<ref>{{cite web|url=http://www.weather.gov/glossary/index.php?word=hail|title=Hail (glossary entry)|publisher=National Oceanic and Atmospheric Administration's National Weather Service|access-date=20 March 2007|url-status=live|archive-url=https://web.archive.org/web/20071127004804/http://www.weather.gov/glossary/index.php?word=hail|archive-date=27 November 2007}}</ref> This form of precipitation is also referred to as "sleet" by the United States [[National Weather Service]].<ref>{{cite web|url=http://www.weather.gov/glossary/index.php?word=sleet|title=Sleet (glossary entry)|publisher=National Oceanic and Atmospheric Administration's National Weather Service|access-date=20 March 2007|url-status=live|archive-url=https://web.archive.org/web/20070218030309/http://www.weather.gov/glossary/index.php?word=sleet|archive-date=18 February 2007}}</ref> (In [[British English]] "sleet" refers to [[Rain and snow mixed|a mixture of rain and snow]].) Ice pellets typically form alongside freezing rain, when a wet [[warm front]] ends up between colder and drier atmospheric layers. There, raindrops would both freeze and shrink in size due to evaporative cooling.<ref>{{cite web|website=Weather Questions|url=http://www.weatherquestions.com/What_causes_ice_pellets.htm|title=What causes ice pellets (sleet)?|access-date=8 December 2007|url-status=live|archive-url=https://web.archive.org/web/20071130071143/http://www.weatherquestions.com/What_causes_ice_pellets.htm|archive-date=30 November 2007}}</ref> So-called snow pellets, or [[graupel]], form when multiple water droplets freeze onto snowflakes until a soft ball-like shape is formed.<ref>{{cite web | url = https://sgil.ba.ars.usda.gov/snowsite/rimegraupel/rg.html | title = Rime and Graupel | publisher = [[U.S. Department of Agriculture]] Electron Microscopy Unit, Beltsville Agricultural Research Center | access-date = 2020-03-23 | archive-url = https://web.archive.org/web/20170711205706/https://sgil.ba.ars.usda.gov/snowsite/rimegraupel/rg.html | archive-date = 2017-07-11}}</ref> So-called "[[diamond dust]]" (METAR code ''IC''<ref name="METAR" />), also known as ice needles or ice crystals, forms at temperatures approaching {{convert|-40|C|F}} due to air with slightly higher moisture from aloft mixing with colder, surface-based air.<ref name="glossdia">{{cite encyclopedia|url=http://amsglossary.allenpress.com/glossary/search?p=1&query=diamond+dust&submit=Search|title=Diamond Dust|encyclopedia=Glossary of Meteorology|date=June 2000|publisher=American Meteorological Society|archive-url=https://web.archive.org/web/20090403084329/http://amsglossary.allenpress.com/glossary/search?p=1&query=diamond+dust&submit=Search|archive-date=3 April 2009|access-date=21 January 2010}}</ref>

=== On surfaces ===
As water drips and re-freezes, it can form hanging [[icicle]]s, or [[stalagmite]]-like structures on the ground.<ref>{{cite journal|last=Makkonen |first=Lase |title=Models for the growth of rime, glaze, icicles and wet snow deposits on structures |journal=Philosophical Transactions of the Royal Society of London A |date=15 November 2000 |volume=358 |issue=1776 |pages=2913–2939 |doi=10.1098/rsta.2000.0690 }}</ref> On sloped roofs, buildup of ice can produce an [[Ice dam (roof)|ice dam]], which stops melt water from draining properly and potentially leads to damaging leaks.<ref>{{cite web |title=Dealing with and preventing ice dams |url=https://extension.umn.edu/protecting-home-rain-and-ice/dealing-and-preventing-ice-dams |publisher=[[University of Minnesota]] Extension |access-date=10 April 2024 }}</ref> More generally, [[water vapor]] depositing onto surfaces due to high [[relative humidity]] and then freezing results in various forms of [[atmospheric icing]], or [[frost]]. Inside buildings, this can be seen as ice on the surface of un-insulated windows.<ref>{{cite web |url=http://www.weatherquestions.com/What_causes_frost.htm |title=What causes frost? |website=Weather Questions |access-date=2007-12-05 |url-status=live |archive-url=https://web.archive.org/web/20071210230539/http://www.weatherquestions.com/What_causes_frost.htm |archive-date=2007-12-10 }}</ref> Hoar frost is common in the environment, particularly in the low-lying areas such as [[valley]]s.<ref>{{cite web|url=http://www.weatheronline.co.uk/reports/wxfacts/Frost-hollow.htm|title=Weather Facts: Frost hollow |work=Weather Online UK|url-status=live|archive-url=https://web.archive.org/web/20130212022607/http://www.weatheronline.co.uk/reports/wxfacts/Frost-hollow.htm|archive-date=2013-02-12}}</ref> In Antarctica, temperatures can be so low that [[electrostatic attraction]] is increased to the point hoarfrost on snow sticks together when blown by wind into [[tumbleweed]]-like balls known as [[yukimarimo]].<ref>{{Cite journal|last1=Kameda|first1=T.|last2=Yoshimi|first2=H.|last3=Azuma|first3=N.|last4=Motoyama|first4=H.|date=1999|title=Observation of 'yukimarimo' on the snow surface of the inland plateau, Antarctic ice sheet|journal=Journal of Glaciology|language=en|volume=45|issue=150|pages=394–396|doi=10.1017/S0022143000001891|bibcode=1999JGlac..45..394K|issn=0022-1430|doi-access=free}}</ref> 

Sometimes, drops of water crystallize on cold objects as [[Rime ice|rime]] instead of glaze. Soft rime has a density between a quarter and two thirds that of pure ice,<ref>{{cite journal |last1=Podolskiy |first1=Evgeny Andreevich |last2=Nygaard |first2=Bjørn Egil Kringlebotn |last3=Nishimura |first3=Kouichi |last4=Makkonen |first4=Lasse |last5=Lozowski |first5=Edward Peter |title=Study of unusual atmospheric icing at Mount Zao, Japan, using the Weather Research and Forecasting model |journal=Journal of Geophysical Research: Atmospheres |date=27 June 2012 |volume=112 |issue=D2 |article-number=2011JD017042 |doi=10.1029/2011JD017042 |bibcode=2012JGRD..11712106P }}</ref> due to a high proportion of trapped air, which also makes soft rime appear white. Hard rime is denser, more transparent, and more likely to appear on ships and aircraft.<ref>{{Cite encyclopedia |title=hard rime |encyclopedia=Glossary of Meteorology |url=https://glossary.ametsoc.org/wiki/Hard_rime |date=30 March 2024 |publisher=American Meteorological Society |language=en-US |access-date=11 April 2024 }}</ref><ref>{{Cite encyclopedia |title=soft rime |encyclopedia=Glossary of Meteorology |url=https://glossary.ametsoc.org/wiki/Soft_rime |date=30 March 2024 |publisher=American Meteorological Society |language=en-US |access-date=11 April 2024 }}</ref> Cold wind specifically causes what is known as ''advection frost'' when it collides with objects. When it occurs on plants, it often causes damage to them.<ref>{{Cite journal |last1=Beerling |first1=D. J. |last2=Terry |first2=A. C. |last3=Mitchell |first3=P. L. |last4=Callaghan |first4=T. V. |last5=Gwynn-Jones |first5=D. |last6=Lee |first6=J. A. |date=April 2001 |title=Time to chill: effects of simulated global change on leaf ice nucleation temperatures of subarctic vegetation |url=http://doi.wiley.com/10.2307/2657062 |journal=American Journal of Botany |language=en |volume=88 |issue=4 |pages=628–633 |doi=10.2307/2657062|jstor=2657062 |pmid=11302848 }}</ref> Various methods exist to protect agricultural crops from frost - from simply covering them to using wind machines.<ref name="Pan2023" /><ref>{{cite web |date=June 2010 |title=Wind machines for minimizing cold injury to horticultural crops |url=https://www.ontario.ca/page/wind-machines-minimizing-cold-injury-horticultural-crops |publisher=Ontario state government |access-date=30 May 2024 }}</ref> In recent decades, [[irrigation sprinkler]]s have been calibrated to spray just enough water to preemptively create a layer of ice that would form slowly and so avoid a sudden temperature shock to the plant, and not be so thick as to cause damage with its weight.<ref name="Pan2023">{{cite journal |last1=Pan |first1=Qingmin |last2=Lu |first2=Yongzong |last3=Hu |first3=Huijie |last4=Hu |first4=Yongguang |title=Review and research prospects on sprinkler irrigation frost protection for horticultural crops |journal=Scientia Horticulture |date=15 December 2023 |volume=326 |article-number=112775 |doi=10.1016/j.scienta.2023.112775 }}</ref>

<gallery mode="packed" heights="150px">
File:Saint-Amant 16 Gelée blanche 2008.jpg|Grass partially covered in hoarfrost, 2008
File:Dülmen, Hausdülmen, Distel -- 2021 -- 5079.jpg|Frost on a thistle in [[Dülmen|Hausdülmen]], [[North Rhine-Westphalia]], Germany
File:Frostweb.jpg|A [[spiderweb]] covered in frost
File:Icy Japanese Maple branch, Boxborough, Massachusetts, 2008.jpg|Ice on [[deciduous tree]] after freezing rain
File:Ice on stairway, 1968 (32085554416).jpg|Icicles on a [[stairway]] in [[Seattle]], 1968
File:WindowFrostNewmarketOntario1986.jpg|Fern frost on a window
File:HoarFrost.jpg|Hoar frost atop snow
File:Yukimarimo south pole dawn 2009.jpg|Yukimarimo at [[South Pole Station]], Antarctica, in 2008
</gallery>

==Ablation==
{{main|Ablation}}

[[File:Melting_ice,_pond.jpg|thumb|Different stages of ice melt in a pond]]

[[File:Aufbrechendes Eis auf dem Silvaplaner See bei Tauwetter April 2014 (1).jpg|thumb|The melting of floating ice]]

Ablation of ice refers to both its [[melting]] and its [[dissolution (chemistry)|dissolution]].<ref>{{Cite book |last=Paterson |first=W. S. B. |url=https://books.google.com/books?id=X75dmp9QFbgC |title=Physics of Glaciers |date=1994 |publisher=Butterworth-Heinemann |isbn=978-0-7506-4742-7 |page=27 |language=en}}</ref>

The melting of ice 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]]. When ice melts it absorbs as much energy as would be required to heat an equivalent amount of water by 80&nbsp;°C. While melting, the temperature of the ice surface remains constant at 0&nbsp;°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''<sub>∞</sub>, when ''T''<sub>∞</sub> is less than 3.98&nbsp;°C, and superlinearly when ''T''<sub>∞</sub> is equal to or greater than 3.98&nbsp;°C, with the rate being proportional to (T<sub>∞</sub>&nbsp;−&nbsp;3.98&nbsp;°C)<sup>''α''</sup>, with ''α''&nbsp;=&nbsp;{{sfrac|5|3}} for ''T''<sub>∞</sub> much greater than 8&nbsp;°C, and α&nbsp;=&nbsp;{{sfrac|4|3}} for in between temperatures ''T''<sub>∞</sub>.<ref>{{cite journal|last1=Keitzl|first1=Thomas|last2=Mellado|first2=Juan Pedro|last3=Notz|first3=Dirk|title=Impact of Thermally Driven Turbulence on the Bottom Melting of Ice|journal=Journal of Physical Oceanography|volume=46 |issue=4|pages=1171–1187|doi=10.1175/JPO-D-15-0126.1|year=2016|bibcode=2016JPO....46.1171K|doi-access=free|hdl=2117/189387|hdl-access=free}}</ref>

In salty ambient conditions, dissolution rather than melting often causes the ablation of ice. For example, the temperature of the [[Arctic Ocean]] is generally below the melting point of ablating sea ice. The phase transition from solid to liquid is achieved by mixing [[salt]] 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. However, the dissolution rate is limited by salt concentration and is therefore slower than melting.<ref>{{cite journal|last1=Woods|first1=Andrew W.|title=Melting and dissolving|journal=Journal of Fluid Mechanics|volume=239|pages=429–448|doi=10.1017/S0022112092004476|year=1992|bibcode=1992JFM...239..429W|s2cid=122680287 }}</ref>

==Role in human activities==
===Cooling===
[[File:Yakhchal_radiative_cooling.svg|thumb|right|A schematic showing how the ancient yakhchals used ice to provide radiative cooling]]

Ice has long been valued as a means of cooling. In 400 BC Iran, [[Achaemenid Empire|Persian]] engineers had already developed techniques for ice storage in the desert through the summer months. During the winter, ice was transported from harvesting pools and nearby mountains in large quantities to be stored in specially designed, naturally cooled ''refrigerators'', called [[yakhchal]] (meaning ''ice storage''). Yakhchals were large underground spaces (up to 5000&nbsp;m<sup>3</sup>) that had thick walls (at least two meters at the base) made of a specific type of mortar called ''[[sarooj]]'' made from sand, clay, egg whites, lime, goat hair, and ash. The mortar was resistant to heat transfer, helping to keep the ice cool enough not to melt; it was also impenetrable by water. Yakhchals often included a [[qanat]] and a system of [[windcatcher]]s that could lower internal temperatures to frigid levels, even during the heat of the summer. One use for the ice was to create chilled treats for royalty.<ref>{{cite journal |last1=Hosseini |first1=Bahareh |last2=Namazian |first2=Ali |title=An Overview of Iranian Ice Repositories, an Example of Traditional Indigenous Architecture |journal=METU Journal of the Faculty of Architecture |year=2012 |volume=29 |issue=2 |pages=223–234 |doi=10.4305/METU.JFA.2012.2.10 |hdl=11511/50831 |hdl-access=free }}</ref><ref>{{cite web |url=https://eartharchitecture.org/?p=570 |title=Yakhchal: Ancient Refrigerators |date=9 September 2009 |website=Earth Architecture}}</ref>

====Harvesting====
{{Main|Ice cutting|Ice trade}}
There were thriving industries in 16th–17th century England whereby low-lying areas along the [[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 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.<ref name=cne>{{Cite Collier's|wstitle=Ice}}</ref>

In the United States, the first cargo of ice was sent from New York City to [[Charleston, South Carolina]], in 1799,<ref name=cne/> 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.<ref>{{Cite web |last=Hutton |first=Mercedes |title=The icy side to Hong Kong history |work=[[BBC Travel]] |date=23 January 2020 |url=https://www.bbc.com/travel/story/20200122-the-icy-side-to-hong-kong-history |access-date=23 January 2020 }}</ref>

[[File:Ice Harvesting on Lake St Clair Michigan circa 1905--photograph courtesy Detroit Publishing Company.jpg|thumb|right|upright=1.1|Harvesting ice on [[Lake St. Clair]] in [[Michigan]], c. 1905]]

[[Trieste]] sent ice to [[Egypt]], [[Corfu]], and [[Zante]]; Switzerland, to France; and Germany sometimes was supplied from [[Bavaria]]n lakes.<ref name=cne/> From 1930s and up until 1994, the [[Hungarian Parliament]] building used ice harvested in the winter from [[Lake Balaton]] for air conditioning.<ref>{{Cite web |last=Kay |first=Nathan |title=The secrets and symbols of Hungary's Parliament building |work=[[CNN]] |date=3 January 2019 |url=https://edition.cnn.com/travel/article/secrets-of-the-hungarian-parliament-building/index.html |archive-url=https://web.archive.org/web/20190317194908/https://edition.cnn.com/travel/article/secrets-of-the-hungarian-parliament-building/index.html |archive-date=17 March 2019 }}</ref>

[[Ice house (building)|Ice house]]s 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]] was cooled using a block of ice placed inside it. Many cities had a regular ice [[Delivery (commerce)|delivery]] service during the summer. The advent of artificial refrigeration technology made the delivery of ice obsolete.<ref name="Prewitt2023" />

Ice is still harvested for [[List of ice and snow sculpture events|ice and snow sculpture events]]. For example, a [[swing saw]] is used to get ice for the [[Harbin International Ice and Snow Sculpture Festival]] each year from the frozen surface of the [[Songhua River]].<ref name="coldestcity">{{cite web|url=https://www.smh.com.au/travel/ice-is-money-in-chinas-coldest-city-20081113-62yj.html|title=Ice is money in China's coldest city|date=13 November 2008|agency=AFP|work=The Sydney Morning Herald|access-date=26 December 2009|archive-url=https://web.archive.org/web/20091002152548/http://www.smh.com.au/travel/ice-is-money-in-chinas-coldest-city-20081113-62yj.html|archive-date=2 October 2009}}</ref>

====Artificial production====
{{main|Icemaker}}
[[File:PSM V39 D031 Interior of an ice factory.jpg|thumb|Layout of a late 19th-century ice factory]]
The earliest known written process to artificially make ice is by the 13th-century writings of Arab historian [[Ibn Abu Usaybia]] in his book ''Kitab Uyun al-anba fi tabaqat-al-atibba'' concerning medicine in which Ibn Abu Usaybia attributes the process to an even older author, Ibn Bakhtawayhi, of whom nothing is known.<ref>{{cite book |last1=Weir |first1=Caroline |last2=Weir |first2= Robin |title=Ice Creams, Sorbets & Gelati: The Definitive Guide |date=2010 |page=217}}</ref>

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.<ref name="ashrae">{{cite book |publisher=[[ASHRAE]] |chapter=Ice Manufacture |year=2006 |title=[[ASHRAE Handbook]]: Refrigeration |edition=Inch-Pound |page=34-1 |isbn=1-931862-86-9}}</ref> Most commercial [[icemaker]]s produce three basic types of fragmentary ice: flake, tubular and plate, using a variety of techniques.<ref name="ashrae"/> Large batch ice makers can produce up to 75 tons of ice per day.<ref>{{cite book |last=Rydzewski |first=A. J. |chapter=Mechanical Refrigeration: Ice Making |title=[[Marks' Standard Handbook for Mechanical Engineers]] |date=2007 |edition=11th |publisher=McGraw Hill |location=New York |pages=19–24 |isbn=978-0-07-142867-5}}</ref> In 2002, there were 426 commercial ice-making companies in the United States, with a combined value of shipments of $595,487,000.<ref>U.S. Census Bureau. [https://www.census.gov/prod/ec02/ec0231i312113.pdf "Ice manufacturing: 2002"]. {{webarchive|url=https://web.archive.org/web/20170722052238/https://www.census.gov/prod/ec02/ec0231i312113.pdf |date=22 July 2017 }}. ''2002 Economic Census''.</ref> Home refrigerators can also make ice with a built in [[icemaker]], which will typically make [[ice cube]]s or crushed ice. The first such device was presented in 1965 by [[Frigidaire]].<ref>{{Cite news |last1=Wroclawski |first1=Daniel |title=How Does an Ice Maker Work? |url=https://reviewed.usatoday.com/refrigerators/features/how-does-an-ice-maker-work |newspaper=[[USA Today]] |date=21 July 2015 |language=en |access-date=26 May 2024 }}</ref>

===Land travel===
[[File:2015-10-18 07 36 28 Frost on a car windshield on Tranquility Court in the Franklin Farm section of Oak Hill, Virginia.jpg|thumb|Ice formation on exterior of vehicle windshield]]
Ice forming on [[road]]s is a common winter hazard, and [[black ice]] particularly dangerous because it is very difficult to see. It is both very transparent, and often forms specifically in shaded (and therefore cooler and darker) areas, i.e. beneath [[overpass]]es.<ref>{{Cite web |last=Donegan |first=Brian |date=15 December 2016 |title=What Is Black Ice And Why Is It So Dangerous?  |url=https://weather.com/science/weather-explainers/news/black-ice-winter-weather-explainer |website=[[The Weather Channel]] |language=en |access-date=11 April 2024 }}</ref>

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]]s of vehicles. Often, snow melts, re-freezes, and forms a fragmented layer of ice which effectively "glues" snow to the window. In this case, the frozen mass is commonly removed with [[ice scraper]]s.<ref>{{cite journal |last1=Dhyani |first1=Abhishek |last2=Choi |first2=Wonjae |last3=Golovin |first3=Kevin |last4=Tuteja |first4=Anish |date=4 May 2022 |title=Surface design strategies for mitigating ice and snow accretion |journal=Matter |volume=5 |issue=5 |pages=1423–1454 |doi=10.1016/j.matt.2022.04.012 |doi-access=free }}</ref> A thin layer of ice crystals can also form on the inside surface of car windows during sufficiently cold weather. In the 1970s and 1980s, some vehicles such as the [[Ford Thunderbird]] could be upgraded with heated windshields as the result. This technology fell out of style as it was too expensive and prone to damage, but rear-window [[defroster]]s are cheaper to maintain and so are more widespread.<ref>{{Cite web |title=A brief history of the heated windshield |last=Braithwaite-Smith |first=Gavin |date=14 December 2022 |url=https://www.hagerty.com/media/automotive-history/a-brief-history-of-the-heated-windshield/ |publisher=Hagerty |language=en |access-date=11 April 2024 }}</ref>

[[File:CaminoDeLaVidaLeningrado.ogv|thumb|right|1943 [[American propaganda during World War II|US propaganda]] film explaining how the ice of Lake Ladoga became the Road of Life during [[WWII]]]]

In sufficiently cold places, the layers of ice on water surfaces can get thick enough for [[ice road]]s to be built. Some regulations{{which|date=September 2025}} specify that the minimum safe thickness is {{cvt|4|in|cm|frac=2}} for a person, {{cvt|7|in|cm|frac=2}} for a [[snowmobile]] and {{cvt|15|in|cm|frac=2}} for an [[automobile]] lighter than 5 tonnes. For [[truck]]s, effective thickness varies with load – e.g. a vehicle with 9-ton total weight requires a thickness of {{cvt|20|in|cm|frac=2}}. Notably, the speed limit{{where|reason=Speed limits vary by jurisdiction. It's nonsense to assert this with no geographic context|date=September 2025}} for a vehicle moving at a road which meets its minimum safe thickness is {{cvt|25|km/h}}, going up to {{cvt|35|km/h}} if the road's thickness is 2 or more times larger than the minimum safe value.<ref>{{cite report |last1=Daly |first1=Steven |last2=Connor |first2=Billy |last3=Garron |first3=Jessica |last4=Stuefer |first4=Svetlana |last5=Belz |first5=Nathan |last6=Bjella |first6=Kevin |date=1 February 2023 |title=Design and Operation of Ice Roads |url=https://aidc.uaf.edu/media/1580/ice-road-manual_final.pdf |publisher=[[University of Alaska Fairbanks]] |access-date=11 April 2024 }}</ref> There is a known instance where a railroad has been built on ice.<ref name="Makkonen, L. 1994"/>

<!--Make no claim about relative fame here. Just the facts. This is an encyclopedia, not a cable documentary-->The [[Road of Life]] across [[Lake Ladoga]] operated in the winters of 1941–1942 and 1942–1943, when it was the only land route available to the [[Soviet Union]] to relieve the [[Siege of Leningrad]] by the German [[Army Group North]].<ref>{{cite book |last=Glantz |first=David M. |author-link=David Glantz |date=2001 |title=The Siege of Leningrad, 1941–1944: 900 Days of Terror |url=https://books.google.com/books?id=efZmAAAAMAAJ |location=Staplehurst |publisher=Spellmount |isbn=1-86227-124-0}}</ref>{{rp|76–80}} The trucks moved hundreds of thousands tonnes of supplies into the city, and hundreds of thousands of civilians were evacuated.<ref>{{cite book |last1=Bidlack |first1=Richard |last2=Lomagin |first2=Nikita |title=The Leningrad Blockade, 1941–1944: A New Documentary History from the Soviet Archives |url=https://books.google.com/books?id=-g2b__W4cQAC&pg=PA406 |date=2012 |publisher=Yale University Press |isbn= 978-0-300-11029-6}}</ref> It is now a [[Historic Centre of Saint Petersburg and Related Groups of Monuments|World Heritage Site]].<ref>{{cite web |url=https://whc.unesco.org/en/list/540/multiple=1&unique_number=635 |title=Saint Petersburg and Related Groups of Monuments |work=Unesco World Heritage Centre }}</ref>

===Water-borne travel===
[[File:Frozen Lake Huron- icebreakers and commercial vessels.jpg|thumb|Channel through ice for ship traffic on [[Lake Huron]] with [[ice breaker]]s in background]]
For ships, ice presents two distinct hazards. Firstly, spray and freezing rain can produce an ice build-up on the superstructure of a vessel sufficient to make it unstable, potentially to the point of [[capsizing]].<ref>{{cite journal |last1=Mintu |first1=Shafiul |last2=Molyneux |first2=David |date=15 August 2022 |title=Ice accretion for ships and offshore structures. Part 1 – State of the art review |journal=Ocean Engineering |volume=258 |article-number=111501 |doi=10.1016/j.oceaneng.2022.111501 |bibcode=2022OcEng.25811501M }}</ref> Earlier, crewmembers were regularly forced to manually hack off ice build-up. After 1980s, spraying de-icing chemicals or melting the ice through hot water/steam hoses became more common.<ref>{{cite journal |last1=Rashid |first1=Taimur |last2=Khawaja |first2=Hassan Abbas |last3=Edvardsen |first3=Kåre |date=17 August 2016 |title=Review of marine icing and anti-/de-icing systems |journal=Ocean Engineering |volume=15 |issue=2 |pages=79–87 |doi=10.1080/20464177.2016.1216734 |bibcode=2016JMEnT..15...79R |hdl=10037/10923 |hdl-access=free }}</ref> Secondly, [[iceberg]]s&nbsp;– large masses of ice floating in water (typically created when glaciers reach the sea)&nbsp;– can be dangerous if struck by a ship when underway. Icebergs have been responsible for the sinking of many ships, notably the [[RMS Titanic|RMS ''Titanic'']].<ref>{{cite book |last1=Halpern |first1=Samuel |last2=Weeks |first2=Charles |year=2011 |title=Report into the Loss of the SS ''Titanic'': A Centennial Reappraisal | editor-last = Halpern | editor-first = Samuel | publisher = The History Press | location = Stroud, UK | isbn = 978-0-7524-6210-3 }}</ref>

For [[harbor]]s near the [[geographical pole|pole]]s, being ice-free, ideally all year long, is an important advantage. Examples are [[Murmansk]] (Russia), [[Pechengsky District|Petsamo]] (Russia, formerly Finland), and [[Vardø (town)|Vardø]] (Norway). Harbors which are not ice-free are opened up using specialized vessels, called icebreakers.<ref name="Sahari2021">{{cite journal |last1=Sahari |first1=Aaro |last2=Matala |first2=Saara |date=9 December 2021 |title=Of a titan, winds and power: Transnational development of the icebreaker, 1890–1954 |journal=International Journal of Maritime History |volume=33 |issue=4 |pages=722–747 |doi=10.1177/08438714211062493 |hdl=11250/3105943 |hdl-access=free }}</ref> Icebreakers are also used to open routes through the sea ice for other vessels, as the only alternative is to find the openings called "[[polynya]]s" or "[[Lead (sea ice)|leads]]". A widespread production of icebreakers began during the 19th century. Earlier designs simply had reinforced [[Bow (watercraft)|bows]] in a spoon-like or diagonal shape to effectively crush the ice. Later designs attached a forward [[propeller]] underneath the protruding bow, as the typical rear propellers were incapable of effectively steering the ship through the ice.<ref name="Sahari2021" />

===Air travel===
{{Further|Icing conditions|Carburetor icing}}
[[File:Some Ice on the boots (1527659244).jpg|thumb|right|Rime ice on the leading edge of an aircraft wing. When the build-up is too large, the black [[deicing boot]] inflates to shake it off.<ref>{{cite magazine |url = https://books.google.com/books?id=XygDAAAAMBAJ&dq=Popular+Science+1931+plane&pg=PA28 |title = Overshoes For Planes End Ice Danger |date = November 1931 |magazine = Popular Science |page = 28 |via = Google Books }}</ref><ref>{{cite book |first = William M. |last = Leary |title = We Freeze to Please: A History of NASA's Icing Research Tunnel and the Quest for Flight Safety |date = 2002 |location = Washington, DC |publisher = National Aeronautics and Space Administration |page = 10 |oclc = 49558649 }}</ref>]]
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. In 1919, during the [[Transatlantic flight of Alcock and Brown|first non-stop flight across the Atlantic]], the British aviators Captain [[John Alcock (RAF officer)|John Alcock]] and Lieutenant [[Arthur Whitten Brown]] encountered such icing conditions&nbsp;– 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.<ref>{{cite web |date=22 July 2014 |title=Capt. John Alcock and Lt. Arthur Whitten Brown |url=http://www.aviation-history.com/airmen/alcock.htm |publisher=The Aviation History On-Line Museum }}</ref>

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. Between 1969 and 1975, 468 such instances were recorded, causing 75 aircraft losses, 44 fatalities and 202 serious injuries.<ref>{{cite journal |last1=Newman |first1=Richard L. |year=1981 |title=Carburetor Ice Flight Testing: Use of an Anti-Icing Fuel Additive |journal=Journal of Aircraft |volume=18 |issue=1 |pages=5–6 |doi=10.2514/3.57458 }}</ref> Thus, [[Carburetor heat|carburetor air intake heaters]] were developed. Further, reciprocating engines with [[fuel injection]] do not require carburetors in the first place.<ref>{{cite book
| title=Pilot's Handbook of Aeronautical Knowledge, FAA-H-8083-25B |date=2016 |publisher=US Department of Transportation, Federal Aviation Administration |pages=7–10 |url=https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/09_phak_ch7.pdf |chapter=Chapter 7: Aircraft Systems |archive-date=2022-12-06 |archive-url=https://web.archive.org/web/20221206115041/https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/09_phak_ch7.pdf |quote=Carburetor heat is an anti-icing system that preheats the air before it reaches the carburetor and is intended to keep the fuel-air mixture above freezing to prevent the formation of carburetor ice. |access-date=2023-02-26}}</ref>

Jet engines do not experience carburetor icing, but they can be affected by the moisture inherently present in [[jet fuel]] freezing and forming ice crystals, which can potentially clog up fuel intake to the engine. Fuel heaters and/or de-icing additives are used to address the issue.<ref>{{cite journal |last1=Schmitz |first1=Mathias |last2=Schmitz |first2=Gerhard |date=15 August 2022 |title=Experimental study on the accretion and release of ice in aviation jet fuel |journal=Aerospace Science and Technology |volume=83 |pages=294–303 |doi=10.1016/j.oceaneng.2022.111501 |bibcode=2022OcEng.25811501M }}</ref>

===Recreation and sports===
{{Main|Ice sports}}
[[File:SCENEONICE.jpg|thumb|''Skating fun'' by 17th century Dutch painter [[Hendrick Avercamp]]]]

Ice plays a central role in winter recreation and in many sports such as [[ice skating]], [[tour skating]], [[ice hockey]], [[bandy]], [[ice fishing]], [[ice climbing]], [[curling]], [[broomball]] and sled racing on [[bobsled]], [[luge]] and [[Skeleton (sport)|skeleton]]. Many of the different sports played on ice get international attention every four years during the [[Winter Olympic Games]].<ref>{{cite journal |last1=Dichter |first1=Heather L. |last2=Teetzel |first2=Sarah |date=23 March 2021 |title=The Winter Olympics: A Century of Games on Ice and Snow |journal=The International Journal of the History of Sport |volume=37 |issue=13 |pages=1215–1235 |doi=10.1080/09523367.2020.1866474  }}</ref>

Small boat-like craft can be mounted on blades and be driven across the ice by [[sails]]. This sport is known as [[ice yachting]], and it had been practiced for centuries.<ref>{{Cite web|url=https://hvmag.com/things-to-do/explore-the-history-of-ice-yachting-in-the-hudson-valley/|title=Explore the History of Ice Yachting in the Hudson Valley|last=Levine|first=David|website=www.hvmag.com|date=19 November 2013 |language=en|access-date=April 14, 2020}}</ref><ref>{{Cite web|url=https://ice.idniyra.org/|title=IDNIYRA {{!}} International DN Ice Yacht Racing Association|date=December 27, 2017|archive-url=https://web.archive.org/web/20171227121944/https://ice.idniyra.org/|access-date=April 15, 2020|archive-date=December 27, 2017}}</ref> Another vehicular sport is [[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 rink]]s.<ref>{{cite web |url=http://www.motortrend.com/features/112_0407_ice_racing/index.html|title=Racing Fast 'n' Cheap: Ice Racing |last=Markus |first=Frank |website=[[Motor Trend]] |access-date=2008-09-30 |archive-date=2011-06-04 |archive-url=https://web.archive.org/web/20110604072725/http://www.motortrend.com/features/112_0407_ice_racing/index.html }}</ref>

===Other uses===
[[File:Ice_sculptor at work (12714055883).jpg|thumb|Carving an ice sculpture]]
==== As thermal ballast ====
* Ice is still used to cool and preserve food in portable [[cooler]]s.<ref name="Prewitt2023">{{Cite web |last1=Prewitt |first1=Laura |date=23 July 2023 |title=A Chilling History |url=https://www.sciencehistory.org/collections/blog/a-chilling-history/ |publisher=[[Science History Institute]] |language=en |access-date=26 April 2024 }}</ref>
*[[Ice cube]]s or [[crushed ice]] can be used to cool drinks. As the ice melts, it absorbs heat and keeps the drink near {{convert|0|C}}.<ref>{{Cite magazine |last1=Bramen |first1=Lisa |date=12 August 2011 |title=Why Don't Other Countries Use Ice Cubes? |url=https://www.smithsonianmag.com/arts-culture/why-dont-other-countries-use-ice-cubes-50361097/ |access-date=26 April 2024 |magazine=[[Smithsonian (magazine)|Smithsonian]] |language=en}}</ref>
* Ice can be used as part of an [[Ice storage air conditioning|air conditioning system]], using battery- or [[solar power|solar-powered]] fans to blow hot air over the ice. This is especially useful during [[heat wave]]s when power is out and standard (electrically powered) air conditioners do not work.<ref>{{cite web |date=4 May 2017 |title=California utility augments 1,800 air conditioning units with 'ice battery' |url=https://arstechnica.com/business/2017/05/ice-batteries-commissioned-by-utility-will-cool-california-businesses/ |website=[[Ars Technica]] }}</ref>
* Ice can be used (like other [[cold pack]]s) to reduce swelling (by decreasing blood flow) and pain by pressing it against an area of the body.<ref>{{cite book | title=The U.S. Navy Seal Guide to Fitness and Nutrition | first1=Patricia A. | last1=Deuster | first2=Anita | last2=Singh | first3=Pierre A. | last3=Pelletier | publisher=Skyhorse | year=2007 | isbn=978-1-60239-030-0 | page=117 | url=https://books.google.com/books?id=3P038jE18BwC&pg=PT117 }}</ref>

==== As structural material ====
[[File:USNS Southern Cross at the ice pier in 1983.jpg|thumb|Ice pier during 1983 cargo operations. [[McMurdo Station]], Antarctica.]]
* Engineers used the substantial strength of pack ice when they constructed Antarctica's first floating [[ice pier]] in 1973.<ref>{{cite news |url=http://antarcticsun.usap.gov/pastIssues/2005-2006/2006_01_08.pdf#page=3 |title=Unique ice pier provides harbor for ships |archive-url=http://archive.wikiwix.com/cache/20110223145229/http://antarcticsun.usap.gov/pastIssues/2005-2006/2006_01_08.pdf |archive-date=23 February 2011 |newspaper=Antarctic Sun |date=8 January 2006 |location=McMurdo Station, Antarctica}}</ref> 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 {{convert|22|ft|m}}. Ice piers are inherently temporary structures, although some can last as long as 10 years. Once a pier is no longer usable, it is towed to sea with an icebreaker.<ref>{{cite web |date=10 February 2023 |title=Ocean Disposal of Man-Made Ice Piers |url=https://www.epa.gov/marine-protection-permitting/ocean-disposal-man-made-ice-piers |publisher=[[United States Environmental Protection Agency]] |url-status=live |archive-url=https://web.archive.org/web/20230701024353/https://www.epa.gov/ocean-dumping/ocean-disposal-man-made-ice-piers |archive-date=1 July 2023 }}</ref>

[[File:Castello di neve in lapponia 02 (2108559776).jpg|thumb|An ice-made dining room of the [[SnowCastle of Kemi]] ice hotel in [[Finland]]]]
* Structures and [[ice sculpture]]s are built out of large chunks of ice or by spraying water<ref name="Makkonen, L. 1994">{{cite book |last=Makkonen |first=L. |year=1994 |title=Ice and Construction |publisher=E & FN Spon |location=London |isbn=0-203-62726-1}}</ref> The structures are mostly ornamental (as in the case with [[Ice palace|ice castle]]s), and not practical for long-term habitation. [[Ice hotel]]s exist on a seasonal basis in a few cold areas.<ref>{{cite news |last=O'Brien |first=Harriet |date=19 January 2007 |title=Ice Hotels: Cold comforts |newspaper=[[The Independent]] |url=https://www.independent.co.uk/travel/europe/ice-hotels-cold-comforts-432813.html |access-date=26 May 2024 }}</ref> [[Igloo]]s are another example of a temporary structure, made primarily from snow.<ref>{{cite news |last=Cruickshank |first=Dan |date=2 April 2008 |title=What house-builders can learn from igloos |work=[[BBC News]] |url=http://news.bbc.co.uk/1/hi/magazine/7326031.stm |access-date=26 May 2024 |url-status=live |archive-url=https://web.archive.org/web/20090311170506/http://news.bbc.co.uk/1/hi/magazine/7326031.stm |archive-date=11 March 2009 }}</ref> 
* Engineers can also use ice to destroy. In [[mining]], drilling holes in rock structures and then pouring water during cold weather is an accepted alternative to using [[dynamite]], as the rock cracks when the water expands as ice.<ref name="Akyurt2002" />
* During World War II, [[Project Habbakuk]] was an Allied 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 vessel immune to torpedoes, and a large deck, could be constructed by ice. A small-scale prototype was built,<ref>{{cite book |last=Gold |first=L. W. |year=1993 |title=The Canadian Habbakuk Project: a Project of the National Research Council of Canada |publisher=International Glaciological Society |isbn=0-946417-16-4}}</ref> but it soon turned out the project would cost far more than a conventional aircraft carrier while being many times slower and also vulnerable to melting.<ref>{{cite news |url=http://www.goodeveca.net/CFGoodeve/habakkuk.html |title=The Ice Ship Fiasco |first=Charles |last=Goodeve |newspaper=Evening Standard |location=London |date=19 April 1951 }}</ref> 
* Ice has even been used as the material for a variety of musical instruments, for example by percussionist [[Terje Isungset]].<ref>{{cite web | url=https://www.bbc.co.uk/music/reviews/cj63 | title=Terje Isungset Iceman Is Review | website=BBC Music | last=Talkington |first=Fiona | date=3 May 2005 | access-date=24 May 2011 | url-status=live | archive-url=https://web.archive.org/web/20130924045635/http://www.bbc.co.uk/music/reviews/cj63 | archive-date=24 September 2013 }}</ref>

==Impacts of climate change==
{{See also|Climate change in the Arctic|Climate change in Antarctica}}

===Historical===

[[File:20210125 The Cryosphere - Floating and grounded ice - imbalance - climate change.png|thumb|upright=1.35| Earth lost 28 trillion tonnes of ice between 1994 and 2017, with melting grounded ice (ice sheets and glaciers) raising the global sea level by 34.6 ±3.1 mm.<ref name="Slater2021" /> The rate of ice loss has risen by 57% since the 1990s − from 0.8 to 1.2 trillion tonnes per year.<ref name="Slater2021" />]]
[[File:Slater 2021 global ice loss.png|thumb|On average, climate change has lowered the thickness of land ice with every year, and reduced the extent of sea ice cover.<ref name="Slater2021" />]]
[[Greenhouse gas emissions]] from human activities unbalance the [[Earth's energy budget]] and so cause an accumulation of [[heat]].<ref name="vonSchuckmann2023" /> About 90% of that heat is added to [[ocean heat content]], 1% is retained in the atmosphere and 3–4% goes to melt major parts of the cryosphere.<ref name="vonSchuckmann2023">{{cite journal |last1=von Schuckmann |first1=Karina |last2=Minière |first2=Audrey |last3=Gues |first3=Flora |last4=Cuesta-Valero |first4=Francisco José |last5=Kirchengast |first5=Gottfried |last6=Adusumilli |first6=Susheel |last7=Straneo |first7=Flammetta |last8=Ablain |first8=Michaël |last9=Allen |first9=Richard P. |last10=Barker |first10=Paul M. |display-authors=6 |title=Heat stored in the Earth system 1960–2020: where does the energy go? |journal=Earth System Science Data |date=17 April 2023 |doi=10.5194/essd-15-1675-2023 |doi-access=free |volume=15 |issue=4 |pages=1675–1709 |bibcode=2023ESSD...15.1675V |hdl=20.500.11850/619535 |hdl-access=free }} [[File:CC-BY icon.svg|50px]] This article incorporates text from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref> Between 1994 and 2017, 28 trillion tonnes of ice were lost around the globe as the result.<ref name="Slater2021" /> [[Arctic sea ice decline]] accounted for the single largest loss (7.6 trillion tonnes), followed by the melting of Antarctica's [[ice shelves]] (6.5 trillion tonnes), the [[Retreat of glaciers since 1850|retreat of mountain glaciers]] (6.1 trillion tonnes), the melting of the [[Greenland ice sheet]] (3.8 trillion tonnes) and finally the melting of the [[Antarctic ice sheet]] (2.5 trillion tonnes) and the limited losses of the sea ice in the [[Southern Ocean]] (0.9 trillion tonnes).<ref name="Slater2021">{{cite journal |last1=Slater |first1=Thomas |last2=Lawrence |first2=Isobel R. |last3=Otosaka |first3=Inès N. |last4=Shepherd |first4=Andrew |last5=Gourmelen |first5=Noel |last6=Jakob |first6=Livia |last7=Tepes |first7=Paul |last8=Gilbert |first8=Lin |last9=Nienow |first9=Peter |display-authors=6 |title=Review article: Earth's ice imbalance |journal=The Cryosphere |date=25 January 2021 |doi=10.5194/tc-15-233-2021 |doi-access=free |volume=15 |issue=1 |pages=233–246 |bibcode=2021TCry...15..233S |hdl=20.500.11820/df343a4d-6b66-4eae-ac3f-f5a35bdeef04 |hdl-access=free }} [[File:CC-BY icon.svg|50px]] This article incorporates text from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>

Other than the sea ice (which already displaces water due to [[Archimedes' principle]]), these losses are a major cause of [[sea level rise]] (SLR) and they are expected to intensify in the future. In particular, the melting of the [[West Antarctic ice sheet]] may accelerate substantially as the floating [[ice shelf|ice shelves]] are lost and can no longer buttress the glaciers. This would trigger poorly understood [[marine ice sheet instability]] processes, which could then increase the SLR expected for the end of the century (between {{cvt|30|cm|ft|frac=2}} and {{cvt|1|m|ft|frac=2}}, depending on future warming), by tens of centimeters more.<ref name="IPCC AR6 WG1 Ch.9">{{Cite journal |last1=Fox-Kemper |first1=B. |last2=Hewitt |first2=Helene T. |author2-link=Helene Hewitt |last3=Xiao |first3=C. |last4=Aðalgeirsdóttir |first4=G. |last5=Drijfhout |first5=S. S. |last6=Edwards |first6=T. L. |last7=Golledge |first7=N. R. |last8=Hemer |first8=M. |last9=Kopp |first9=R. E. |last10=Krinner |first10=G. |last11=Mix |first11=A. |display-authors=6 |date=2021 |editor-last=Masson-Delmotte |editor-first=V. |editor2-last=Zhai |editor2-first=P. |editor3-last=Pirani |editor3-first=A. |editor4-last=Connors |editor4-first=S. L. |editor5-last=Péan |editor5-first=C. |editor6-last=Berger |editor6-first=S. |editor7-last=Caud |editor7-first=N. |editor8-last=Chen |editor8-first=Y. |editor9-last=Goldfarb |editor9-first=L. |display-editors=6 |title=Chapter 9: Ocean, Cryosphere and Sea Level Change |url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter09.pdf |journal=Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change |publisher=Cambridge University Press |location=Cambridge, UK and New York, US }}</ref>{{rp|1302}} 

Ice loss in Greenland and Antarctica also produces large quantities of fresh [[meltwater]], which disrupts the [[Atlantic meridional overturning circulation]] (AMOC) and the [[Southern Ocean overturning circulation]], respectively.<ref name="GTPR2023" /> These two halves of the [[thermohaline circulation]] are very important for the global climate. A continuation of high meltwater flows may cause a severe disruption (up to a point of a "collapse") of either circulation, or even both of them. Either event would be considered an example of [[tipping points in the climate system]], because it would be extremely difficult to reverse.<ref name="GTPR2023">{{cite report |last1=Lenton |first1=T. M. |last2=Armstrong McKay |first2=D.I. |last3=Loriani |first3=S. |last4=Abrams |first4=J. F.  |last5=Lade |first5=S. J. |last6=Donges |first6=J. F. |last7=Milkoreit |first7=M. |last8=Powell |first8=T. |last9=Smith |first9=S. R. |last10=Zimm |first10=C. |last11=Buxton |first11=J. E. |last12=Daube |first12=Bruce C. |last13=Krummel |first13=Paul B. |last14=Loh |first14=Zoë |last15=Luijkx |first15=Ingrid T. |display-authors=6 |year=2023 |title=The Global Tipping Points Report 2023 |url=https://global-tipping-points.org/download/4608/ |publisher=University of Exeter }}</ref> AMOC is generally not expected to collapse during the 21st century, while there is only limited knowledge about the Southern Ocean circulation.<ref name="IPCC AR6 WG1 Ch.9" />{{rp|1214}}

Another example of ice-related tipping point is permafrost thaw. While the organic content in the permafrost causes {{CO2}} and methane emissions once it thaws and begins to decompose,<ref name="GTPR2023" /> ice melting liqufies the ground, causing anything built above the former permafrost to collapse. By 2050, the economic damages from such infrastructure loss are expected to cost tens of billions of dollars.<ref name="Hjort2022">{{Cite journal |last1=Hjort |first1=Jan |last2=Streletskiy |first2=Dmitry |last3=Doré |first3=Guy |last4=Wu |first4=Qingbai |last5=Bjella |first5=Kevin |last6=Luoto |first6=Miska |date=11 January 2022 |title=Impacts of permafrost degradation on infrastructure |journal=Nature Reviews Earth & Environment |volume=3 |issue=1 |pages=24–38 |doi=10.1038/s43017-021-00247-8|bibcode=2022NRvEE...3...24H |hdl=10138/344541 |s2cid=245917456 |url=http://urn.fi/urn:nbn:fi-fe2022101962575 |hdl-access=free }}</ref>

===Predictions===

[[File:Wunderling 2020 regional impact.jpg|thumb|Potential regional warming caused by the loss of all land ice outside of East Antarctica, and by the disappearance of Arctic sea ice every year starting from June.<ref name="Wunderling2020" /> While plausible, consistent sea ice loss would likely require relatively high warming,<ref name="Sigmond2018" /> and the loss of all ice in Greenland would require multiple millennia.<ref name="ArmstrongMcKay2022" /><ref name="ArmstrongMcKayExplainer" />]]

In the future, the [[Arctic Ocean]] is likely to lose effectively all of its sea ice during at least some Septembers (the end of the ice melting season), although some of the ice would refreeze during the winter. That is, an ice-free September is likely to occur once in every 40 years if global warming is at {{convert|1.5|C-change|F-change}}, but would occur once in every 8 years at {{convert|2|C-change|F-change}} and once in every 1.5 years at {{convert|3|C-change|F-change}}.<ref name="Sigmond2018">{{Cite journal |last1=Sigmond |first1=Michael |last2=Fyfe |first2=John C. |last3=Swart  |first3=Neil C. |date=2 April 2018 |title=Ice-free Arctic projections under the Paris Agreement |url=https://www.nature.com/articles/s41558-018-0124-y.epdf?sharing_token=s5CzjtDj8gf0ZmN6CCHGztRgN0jAjWel9jnR3ZoTv0PLVuAXOp2dJlBdNTJtKWqWAUYJ9Ns6JXBlxiHaipJXlrKpbiBcmkhRc42ypYk5a3aeceQ5dF5hV39PYKz05y5seLV8NH9jDQsSxYOgWrLL-CjbZkxrUf6gYwBnx-vAhRL3KTUq_7I1sz5MHuQESHzcuFa8mIqycanI0sYAgJoCzHIjO-WCVh51qA0aONgHJ5s%3D&tracking_referrer=interactive.carbonbrief.org |journal=Nature Climate Change |language=en |volume=2 |issue=5 |pages=404–408 |doi=10.1038/s41558-018-0124-y|bibcode=2018NatCC...8..404S |s2cid=90444686 |url-access=subscription }}</ref> This would affect the regional and global climate due to the [[ice-albedo feedback]]. Because ice is highly reflective of solar energy, persistent sea ice cover lowers local temperatures. Once that ice cover melts, the darker ocean waters begin to absorb more heat, which also helps to melt the remaining ice.<ref name="Dai2019">{{Cite journal |last1=Dai |first1=Aiguo |last2=Luo |first2=Dehai |last3=Song |first3=Mirong |last4=Liu |first4=Jiping |date=10 January 2019 |title=Arctic amplification is caused by sea-ice loss under increasing CO2 |journal=Nature Communications |language=en |volume=10 |issue=1 |page=121 |doi=10.1038/s41467-018-07954-9 |pmid=30631051 |pmc=6328634 |bibcode=2019NatCo..10..121D }}</ref>

Global losses of sea ice between 1992 and 2018, almost all of them in the Arctic, have already had the same impact as 10% of [[greenhouse gas]] emissions over the same period.<ref name="Riihelä2021">{{Cite journal |last1=Riihelä |first1=Aku |last2=Bright |first2=Ryan M. |last3=Anttila |first3=Kati |date=28 October 2021 |title=Recent strengthening of snow and ice albedo feedback driven by Antarctic sea-ice loss |journal=Nature Geoscience |language=en |volume=14 |issue=11 |pages=832–836 |doi=10.1038/s41561-021-00841-x |bibcode=2021NatGe..14..832R |hdl=11250/2830682 |hdl-access=free }}</ref> If all the Arctic sea ice was gone every year between June and September ([[polar day]], when the Sun is constantly shining), temperatures in the Arctic would increase by over {{convert|1.5|C-change|F-change}}, while the global temperatures would increase by around {{convert|0.19|C-change|F-change}}.<ref name="Wunderling2020">{{Cite journal |last1=Wunderling |first1=Nico |last2=Willeit |first2=Matteo |last3=Donges |first3=Jonathan F. |last4=Winkelmann |first4=Ricarda |date=27 October 2020 |title=Global warming due to loss of large ice masses and Arctic summer sea ice |journal=Nature Communications |language=en |volume=10 |issue=1 |page=5177 |doi=10.1038/s41467-020-18934-3 |pmid=33110092 |pmc=7591863 |bibcode=2020NatCo..11.5177W }}</ref>

[[File:Höning 2023 GIS thresholds.jpg|thumb|upright=1.2|Possible equilibrium states of the Greenland ice sheet in response to different equilibrium carbon dioxide concentrations in [[parts per million]]. Second and third states would result in {{convert|1.8|m|ft|0|abbr=on}} and {{convert|2.4|m|ft|0|abbr=on}} of sea level rise, while the fourth state is equivalent to {{convert|6.9|m|ft|0|abbr=on}}.<ref name="Höning2023">{{Cite journal |last1=Höning |first1=Dennis |last2=Willeit |first2=Matteo |last3=Calov |first3=Reinhard |last4=Klemann |first4=Volker |last5=Bagge |first5=Meike |last6=Ganopolski |first6=Andrey |date=27 March 2023 |title=Multistability and Transient Response of the Greenland Ice Sheet to Anthropogenic CO2 Emissions |journal=Geophysical Research Letters |volume=50 |issue=6 |article-number=e2022GL101827 |doi=10.1029/2022GL101827 |s2cid=257774870|doi-access=free }}</ref>]]

By 2100, at least a quarter of mountain glaciers outside of Greenland and Antarctica would melt,<ref>{{Cite journal |last1=Rounce |first1=David R. |last2=Hock |first2=Regine |last3=Maussion |first3=Fabien |last4=Hugonnet |first4=Romain |last5=Kochtitzky |first5=William |last6=Huss |first6=Matthias |last7=Berthier|first7=Etienne |last8=Brinkerhoff |first8=Douglas |last9=Compagno |first9=Loris |last10=Copland |first10=Luke |last11=Farinotti |first11=Daniel |last12=Menounos |first12=Brian |last13=McNabb |first13=Robert W. |display-authors=6 |date=5 January 2023 |title=Global glacier change in the 21st century: Every increase in temperature matters |url=https://www.science.org/doi/10.1126/science.abo1324 |journal=Science |language=en |volume=79 |issue=6627 |pages=78–83 |doi=10.1126/science.abo1324 |pmid=36603094 |bibcode=2023Sci...379...78R |s2cid=255441012 |hdl=10852/108771 |hdl-access=free }}</ref> and effectively all ice caps on non-polar mountains are likely to be lost around 200 years after global warming reaches {{convert|2|C-change|F-change}}.<ref name="ArmstrongMcKay2022" /><ref name="ArmstrongMcKayExplainer" /> The West Antarctic ice sheet is highly vulnerable and will likely disappear even if the warming does not progress further,<ref>{{Cite web|url=https://www.science.org/content/article/discovery-recent-antarctic-ice-sheet-collapse-raises-fears-new-global-flood|title=Discovery of recent Antarctic ice sheet collapse raises fears of a new global flood|last=Voosen|first=Paul|date=2018-12-18|website=Science|language=en|access-date=2018-12-28}}</ref><ref name="Carlson2018">{{Cite conference |last1=Carlson |first1=Anders E. |last2=Walczak |first2=Maureen H. |last3=Beard |first3=Brian L. |last4=Laffin |first4=Matthew K. |last5=Stoner |first5=Joseph S. |last6=Hatfield |first6=Robert G. |date=10 December 2018 |title=Absence of the West Antarctic ice sheet during the last interglaciation |url=https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/421418  |conference=American Geophysical Union Fall Meeting }}</ref><ref name="Naughten2023">{{cite journal |last1=Naughten |first1=Kaitlin A. |last2=Holland |first2=Paul R. |last3=De Rydt |first3=Jan|title=Unavoidable future increase in West Antarctic ice-shelf melting over the twenty-first century |journal=Nature Climate Change |date=23 October 2023 |volume=13 |issue=11 |pages=1222–1228 |doi=10.1038/s41558-023-01818-x |s2cid=264476246 |doi-access=free |bibcode=2023NatCC..13.1222N }}</ref><ref name="Lau2023">{{Cite journal |last1=Lau |first1=Sally C. Y. |last2=Wilson |first2=Nerida G. |last3=Golledge |first3=Nicholas R.  |last4=Naish |first4=Tim R. |last5=Watts |first5=Phillip C. |last6=Silva |first6=Catarina N. S. |last7=Cooke |first7=Ira R. |last8=Allcock |first8=A. Louise |last9=Mark |first9=Felix C. |last10=Linse |first10=Katrin |display-authors=6 |date=21 December 2023 |title=Genomic evidence for West Antarctic Ice Sheet collapse during the Last Interglacial |journal=Science |language=en |volume=382 |issue=6677 |pages=1384–1389 |doi=10.1126/science.ade0664 |pmid=38127761 |bibcode=2023Sci...382.1384L |s2cid=266436146 |url=https://epic.awi.de/id/eprint/58369/1/science.ade0664%281%29.pdf }}</ref> although it could take around 2,000 years before its loss is complete.<ref name="ArmstrongMcKay2022">{{Cite journal |last1=Armstrong McKay |first1=David|last2=Abrams |first2=Jesse |last3=Winkelmann |first3=Ricarda |last4=Sakschewski |first4=Boris |last5=Loriani |first5=Sina |last6=Fetzer |first6=Ingo|last7=Cornell|first7=Sarah |last8=Rockström |first8=Johan |last9=Staal |first9=Arie |last10=Lenton |first10=Timothy |display-authors=6 |date=9 September 2022 |title=Exceeding 1.5°C global warming could trigger multiple climate tipping points |url=https://www.science.org/doi/10.1126/science.abn7950 |journal=Science |language=en |volume=377 |issue=6611 |article-number=eabn7950 |doi=10.1126/science.abn7950 |pmid=36074831 |hdl=10871/131584 |s2cid=252161375 |issn=0036-8075|hdl-access=free |url-access=subscription }}</ref><ref name="ArmstrongMcKayExplainer">{{Cite web |last=Armstrong McKay |first=David |date=9 September 2022 |title=Exceeding 1.5°C global warming could trigger multiple climate tipping points – paper explainer |url=https://climatetippingpoints.info/2022/09/09/climate-tipping-points-reassessment-explainer/ |access-date=2 October 2022 |website=climatetippingpoints.info |language=en}}</ref> The Greenland ice sheet will most likely be lost with the sustained warming between {{convert|1.7|C-change|F-change}} and {{convert|2.3|C-change|F-change}},<ref name="Bochow2023">{{cite journal |last1=Bochow |first1=Nils |last2=Poltronieri |first2=Anna |last3=Robinson |first3=Alexander |last4=Montoya |first4=Marisa |last5=Rypdal |first5=Martin |last6=Boers |first6=Niklas |date=18 October 2023 |title=Overshooting the critical threshold for the Greenland ice sheet |journal=Nature |volume=622 |issue=7983 |pages=528–536 |bibcode=2023Natur.622..528B |doi=10.1038/s41586-023-06503-9 |pmc=10584691 |pmid=37853149}}</ref> although its total loss requires around 10,000 years.<ref name="ArmstrongMcKay2022" /><ref name="ArmstrongMcKayExplainer" /> Finally, the [[East Antarctic ice sheet]] will take at least 10,000 years to melt entirely, which requires a warming of between {{convert|5|C-change|F-change}} and {{convert|10|C-change|F-change}}.<ref name="ArmstrongMcKay2022" /><ref name="ArmstrongMcKayExplainer" />

If all the ice on Earth melted, it would result in about {{Convert|70|m|ftin|abbr=on}} of sea level rise,<ref>{{cite web |title=How would sea level change if all glaciers melted? |url=https://www.usgs.gov/faqs/how-would-sea-level-change-if-all-glaciers-melted |website=United States Geological Survey |date=23 September 2021 |access-date=15 January 2024 }}</ref> with some {{Convert|53.3|m|ftin|abbr=on}} coming from East Antarctica.<ref name="Fretwell2013">{{cite journal |last1=Fretwell |first1=P. |last2=Pritchard |first2=H. D. |last3=Vaughan |first3=D. G. |last4=Bamber |first4=J. L. |last5=Barrand |first5=N. E. |last6=Bell |first6=R. |last7=Bianchi |first7=C. |last8=Bingham |first8=R. G. |last9=Blankenship |first9=D. D. |last10=Casassa |first10=G. |last11=Catania |first11=G. |last12=Callens |first12=D. |last13=Conway |first13=H. |last14=Cook |first14=A. J. |last15=Corr |first15=H. F. J. |last16=Damaske |first16=D. |last17=Damm |first17=V. |last18=Ferraccioli |first18=F. |last19=Forsberg |first19=R. |last20=Fujita |first20=S. |last21=Gim |first21=Y. |last22=Gogineni |first22=P. |last23=Griggs |first23=J. A. |last24=Hindmarsh |first24=R. C. A. |last25=Holmlund |first25=P. |last26=Holt |first26=J. W. |last27=Jacobel |first27=R. W. |last28=Jenkins |first28=A. |last29=Jokat |first29=W. |last30=Jordan |first30=T. |last31=King |first31=E. C. |last32=Kohler |first32=J. |last33=Krabill |first33=W. |last34=Riger-Kusk |first34=M. |last35=Langley |first35=K. A. |last36=Leitchenkov |first36=G. |last37=Leuschen |first37=C. |last38=Luyendyk |first38=B. P. |last39=Matsuoka |first39=K. |last40=Mouginot |first40=J. |last41=Nitsche |first41=F. O. |last42=Nogi |first42=Y. |last43=Nost |first43=O. A. |last44=Popov |first44=S. V. |last45=Rignot |first45=E. |last46=Rippin |first46=D. M. |last47=Rivera |first47=A. |last48=Roberts |first48=J. |last49=Ross |first49=N. |last50=Siegert |first50=M. J. |last51=Smith |first51=A. M. |last52=Steinhage |first52=D. |last53=Studinger |first53=M. |last54=Sun |first54=B. |last55=Tinto |first55=B. K. |last56=Welch |first56=B. C. |last57=Wilson |first57=D. |last58=Young |first58=D. A. |last59=Xiangbin |first59=C. |last60=Zirizzotti |first60=A. |display-authors=6 |title=Bedmap2: improved ice bed, surface and thickness datasets for Antarctica |journal=The Cryosphere |date=28 February 2013 |volume=7 |issue=1 |pages=375–393 |doi=10.5194/tc-7-375-2013 |bibcode=2013TCry....7..375F |doi-access=free |hdl=1808/18763 |hdl-access=free }}</ref> Due to [[isostatic rebound]], the ice-free land would eventually become {{Convert|301|m|ftin|abbr=on}} higher in Greenland and {{Convert|494|m|ftin|abbr=on}} in Antarctica, on average. Areas in the center of each landmass would become up to {{Convert|783|m|ftin|abbr=on}} and {{Convert|936|m|ftin|abbr=on}} higher, respectively.<ref>{{Cite journal |last1=Paxman |first1=Guy J. G. |last2=Austermann |first2=Jacqueline |last3=Hollyday |first3=Andrew |date=6 July 2022 |title=Total isostatic response to the complete unloading of the Greenland and Antarctic Ice Sheets |journal=Scientific Reports |volume=12 |issue=1 |page=11399 |doi=10.1038/s41598-022-15440-y |pmid=35794143 |pmc=9259639 |bibcode=2022NatSR..1211399P }}</ref> The impact on global temperatures from losing West Antartica, mountain glaciers and the Greenland ice sheet is estimated at {{convert|0.05|C-change|F-change}}, {{convert|0.08|C-change|F-change}} and {{convert|0.13|C-change|F-change}}, respectively,<ref name="Wunderling2020" /> while the lack of the East Antarctic ice sheet would increase the temperatures by {{convert|0.6|C-change|F-change}}.<ref name="ArmstrongMcKay2022" /><ref name="ArmstrongMcKayExplainer" />

==Non-water==
{{main|Volatile (astrogeology)}}
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 or [[Sublimation (chemistry)|sublimation]] point lies above or around {{convert|100|K|C F}} (assuming standard atmospheric pressure). The best known example is [[dry ice]], the solid form of [[carbon dioxide]]. Its sublimation/deposition point occurs at {{convert|194.7|K|C F}}.<ref>{{Cite journal|last=Barber|first=C R|date=March 1966|title=The sublimation temperature of carbon dioxide|url=https://iopscience.iop.org/article/10.1088/0508-3443/17/3/312|journal=British Journal of Applied Physics|language=en|volume=17|issue=3|pages=391–397|doi=10.1088/0508-3443/17/3/312|bibcode=1966BJAP...17..391B|issn=0508-3443|access-date=2020-11-15|archive-date=2021-06-29|archive-url=https://web.archive.org/web/20210629110924/https://iopscience.iop.org/article/10.1088/0508-3443/17/3/312|url-status=live|url-access=subscription}}</ref>

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]].<ref>{{cite journal |last1=Ramirez |first1=A. P. |last2=Hayashi |first2=A. |last3=Cava |first3=R.J. |last4=Siddharthan |first4=R. |last5=Shastry |first5=B. S. |date=27 May 1999 |title=Zero-point entropy in 'spin ice' |journal=Nature |volume=399 |issue=3 |pages=333–335 |doi=10.1038/20619 |bibcode=1999Natur.399..333R }}</ref>

==See also==
{{portal|Water}}
{{div col}}
* {{annotated link|Ice famine}}
* {{annotated link|Ice jacking}}
* {{annotated link|Jumble ice}}
* {{annotated link|Pumpable ice technology}}
{{div col end}}

==References==
{{Reflist}}

==Further reading==
* Brady, Amy. ''Ice: From Mixed Drinks to Skating Rinks--A Cool History of a Hot Commodity'' (G. P. Putnam's Sons, 2023).
* Hogge, Fred. ''Of Ice and Men: How We've Used Cold to Transform Humanity'' (Pegasus Books, 2022) 
* Leonard, Max. ''A Cold Spell: A Human History of Ice'' (Bloomsbury, 2023) [http://www.h-net.org/reviews/showrev.php?id=60582 online review of this book]

==External links==
{{Wiktionary}}
{{Commons category|Ice}}
{{NSRW Poster}}
* [http://www.webmineral.com/data/Ice.shtml Webmineral listing for Ice]
* [http://www.mindat.org/min-2001.html MinDat.org listing and location data for Ice]
* [http://www.sciencebits.com/StandingOnIce Estimating the bearing capacity of ice]
* [https://phys.org/news/2007-03-sandia-machine-ice-nanoseconds.html High-temperature, high-pressure ice]
* [https://web.archive.org/web/20090318135129/http://blogs.static.mentalfloss.com/blogs/archives/20311.html The Surprisingly Cool History of Ice]

{{Ice |expanded}}
{{Natural resources}}

{{Authority control}}

[[Category:Ice| ]]
[[Category:Water ice| ]]
[[Category:Glaciology]]
[[Category:Minerals]]
[[Category:Transparent materials]]
[[Category:Articles containing video clips]]
[[Category:Limnology]]
[[Category:Oceanography]]
[[Category:Cryosphere]]