Editing Cryosphere

{{Short description|Earth's surface where water is frozen}}
{{For|the scientific journal|The Cryosphere}}
[[File:Cryosphere Fuller Projection.png|thumb|right|300px|Overview of the cryosphere and its larger components<ref>{{Cite web |date=2007-08-26 |title=Cryosphere - Maps and Graphics at UNEP/GRID-Arendal |url=http://maps.grida.no/go/graphic/cryosphere |access-date=2023-09-25 |archive-url=https://web.archive.org/web/20070826211613/http://maps.grida.no/go/graphic/cryosphere |archive-date=2007-08-26 }}</ref>]]
The '''cryosphere''' is an umbrella term for those portions of [[Earth]]'s surface where water is in solid form. This includes [[sea ice]], [[ice]] on lakes or rivers, [[snow]], [[glacier]]s, [[ice cap]]s, [[ice sheet]]s, and frozen ground (which includes [[permafrost]]). Thus, there is an overlap with the [[hydrosphere]]. The cryosphere is an integral part of the global [[climate system]]. It also has important [[Climate change feedbacks|feedbacks on the climate system]]. These feedbacks come from the cryosphere's influence on surface energy and moisture fluxes, [[cloud]]s, the [[water cycle]], atmospheric and [[Ocean circulation|oceanic circulation]].

Through these feedback processes, the cryosphere plays a significant role in the [[global climate]] and in [[climate model]] response to global changes. Approximately 10% of the Earth's surface is covered by ice, but this is rapidly decreasing.<ref>{{cite web |title=Global Ice Viewer – Climate Change: Vital Signs of the Planet |url=https://climate.nasa.gov/interactives/global-ice-viewer/#/ |website=climate.nasa.gov |access-date=27 November 2021}}</ref> Current reductions in the cryosphere ([[Effects of climate change|caused by climate change]]) are measurable in [[Ice sheet#Melting due to climate change|ice sheet melt]], [[Retreat of glaciers since 1850|glaciers decline]], [[Effects of climate change#Sea ice decline|sea ice decline]], [[permafrost thaw]] and snow cover decrease.

== Definition and terminology ==
The cryosphere describes those portions of [[Earth]]'s surface where water is in solid form. Frozen water is found on the [[Earth]]'s surface primarily as [[snow]] cover, [[freshwater]] ice in [[lake]]s and [[river]]s, [[sea ice]], [[glaciers]], [[ice sheets]], and frozen ground and [[permafrost]] (permanently frozen ground). 

The cryosphere is one of five components of the [[climate system]]. The others are the [[Atmosphere of Earth|atmosphere]], the [[hydrosphere]], the [[lithosphere]] and the [[biosphere]].<ref name=":0" />{{rp|1451}}

The term ''cryosphere'' comes from the [[Ancient Greek|Greek]] word ''kryos'', meaning ''cold'', ''frost'' or ''ice'' and the Greek word ''sphaira'', meaning ''globe'' or ''ball''.<ref>[https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dsfai%3Dra^ σφαῖρα] {{Webarchive|url=https://web.archive.org/web/20170510152357/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dsfai%3Dra%5E|date=2017-05-10}}, Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus</ref>

''Cryospheric sciences'' is an [[umbrella term]] for the study of the cryosphere. As an interdisciplinary [[Earth science]], many disciplines contribute to it, most notably [[geology]], [[hydrology]], and [[meteorology]] and [[climatology]]; in this sense, it is comparable to [[glaciology]].

The term ''[[deglaciation]]'' describes the retreat of cryospheric features.

== Properties and interactions ==
[[File:Climate-system.jpg|alt=|thumb|330x330px|The cryosphere (bottom left) is one of five components of the [[climate system]]. The others are the [[Atmosphere of Earth|atmosphere]], the [[hydrosphere]], the [[lithosphere]] and the [[biosphere]].<ref name=":0"> {{cite book |last=Planton |first=S. |title=Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change |publisher=Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. |year=2013 |editor-last=Stocker |editor-first=T.F. |chapter=Annex III: Glossary |editor-last2=Qin |editor-first2=D. |editor-last3=Plattner |editor-first3=G.-K. |editor-last4=Tignor |editor-first4=M. |editor-last5=Allen |editor-first5=S.K. |editor-last6=Boschung |editor-first6=J. |editor-last7=Nauels |editor-first7=A. |editor-last8=Xia |editor-first8=Y. |editor-last9=Bex |editor-first9=V. |chapter-url=https://www.ipcc.ch/site/assets/uploads/2018/08/WGI_AR5_glossary_EN.pdf |editor-first10=P.M. |editor-last10=Midgley}}</ref>{{rp|1451}}]]There are several fundamental physical properties of snow and ice that modulate energy exchanges between the surface and the [[atmosphere]]. The most important properties are the surface reflectance ([[albedo]]), the ability to transfer heat (thermal diffusivity), and the ability to change state ([[latent heat]]). These physical properties, together with surface roughness, [[emissivity]], and [[dielectric]] characteristics, have important implications for observing snow and ice from space. For example, surface roughness is often the dominant factor determining the strength of [[radar]] [[backscatter]].<ref name="hall">{{cite book |last1=Hall |first1=Dorothy K. |author-link=Dorothy Hall (scientist)|title=Remote Sensing of Ice and Snow |date=1985 |publisher=Springer Netherlands |location=Dordrecht |isbn=978-94-009-4842-6}}</ref> Physical properties such as [[crystal]] structure, density, length, and liquid water content are important factors affecting the transfers of heat and water and the scattering of [[microwave]] [[energy]].

=== Residence time and extent ===
The residence time of water in each of the cryospheric sub-systems varies widely. Snow cover and freshwater ice are essentially seasonal, and most sea ice, except for ice in the central [[Arctic]], lasts only a few years if it is not seasonal. A given water particle in glaciers, ice sheets, or ground ice, however, may remain frozen for 10–100,000 years or longer, and deep ice in parts of [[East Antarctica]] may have an age approaching 1 million years.{{citation needed|date=September 2023}}

Most of the world's ice volume is in [[Antarctica]], principally in the [[East Antarctic Ice Sheet]]. In terms of areal extent, however, [[Northern Hemisphere]] winter snow and ice extent comprise the largest area, amounting to an average 23% of hemispheric surface area in January. The large areal extent and the important climatic roles of snow and [[ice]] is related to their unique physical properties. This also indicates that the ability to observe and model snow and ice-cover extent, thickness, and [[Properties of water#Physics and chemistry|physical properties]] (radiative and thermal properties) is of particular significance for [[Climatology|climate research]].<ref>{{Cite web |title=Properties of Snow – Our Winter World |url=https://ourwinterworld.org/snow-science/properties-of-snow/ |archive-url=http://web.archive.org/web/20250115030453/https://ourwinterworld.org/snow-science/properties-of-snow/ |archive-date=2025-01-15 |access-date=2025-03-06 |website=ourwinterworld.org |language=en-US}}</ref>

=== Surface reflectance ===
The surface reflectance of incoming [[solar radiation]] is important for the surface energy balance (SEB). It is the ratio of reflected to incident solar radiation, commonly referred to as [[albedo]]. Climatologists are primarily interested in albedo integrated over the [[Shortwave radiation|shortwave]] portion of the [[electromagnetic spectrum]] (~300 to 3500&nbsp;nm), which coincides with the main solar energy input. Typically, albedo values for non-melting snow-covered surfaces are high (~80–90%) except in the case of forests.{{citation needed|date=September 2023}} 

The higher albedos for snow and ice cause rapid shifts in surface [[reflectivity]] in autumn and spring in high latitudes, but the overall climatic significance of this increase is spatially and temporally modulated by [[cloud cover]]. (Planetary albedo is determined principally by cloud cover, and by the small amount of total solar radiation received in high [[latitudes]] during winter months.) Summer and autumn are times of high-average cloudiness over the [[Arctic Ocean]] so the albedo [[feedback]] associated with the large seasonal changes in sea-ice extent is greatly reduced. It was found that snow cover exhibited the greatest influence on [[Earth's energy budget|Earth's radiative balance]] in the spring (April to May) period when incoming [[solar radiation]] was greatest over snow-covered areas.<ref name="groisman">{{cite journal |last1=Groisman |first1=Pavel Ya. |last2=Karl |first2=Thomas R. |last3=Knight |first3=Richard W. |title=Observed Impact of Snow Cover on the Heat Balance and the Rise of Continental Spring Temperatures |journal=Science |date=14 January 1994 |volume=263 |issue=5144 |pages=198–200 |doi=10.1126/science.263.5144.198 |pmid=17839175 |bibcode=1994Sci...263..198G |s2cid=9932394 |url=https://www.science.org/doi/10.1126/science.263.5144.198 |access-date=25 February 2022}}</ref>

=== Thermal properties of cryospheric elements ===
The [[Heat|thermal]] properties of cryospheric elements also have important climatic consequences.{{citation needed|date=September 2023}} Snow and ice have much lower thermal diffusivities than [[air]]. [[Thermal diffusivity]] is a measure of the speed at which temperature waves can penetrate a substance. Snow and ice are many [[orders of magnitude]] less efficient at diffusing heat than air. Snow cover insulates the ground surface, and sea ice insulates the underlying ocean, decoupling the surface-atmosphere interface with respect to both heat and moisture fluxes. The flux of moisture from a water surface is eliminated by even a thin skin of ice, whereas the flux of heat through thin ice continues to be substantial until it attains a thickness in excess of 30 to 40&nbsp;cm. However, even a small amount of snow on top of the ice will dramatically reduce the heat flux and slow down the rate of ice growth. The insulating effect of snow also has major implications for the [[hydrological cycle]]. In non-permafrost regions, the insulating effect of snow is such that only near-surface ground freezes and deep-water drainage is uninterrupted.<ref name="lynch">Lynch-Stieglitz, M., 1994: The development and validation of a simple snow model for the GISS GCM. J. Climate, 7, 1842–1855.</ref>

While snow and ice act to insulate the surface from large energy losses in winter, they also act to retard warming in the spring and summer because of the large amount of energy required to melt ice (the [[latent heat]] of fusion, 3.34 x 10<sup>5</sup> J/kg at 0&nbsp;°C). However, the strong static stability of the atmosphere over areas of extensive snow or ice tends to confine the immediate cooling effect to a relatively shallow layer, so that associated atmospheric anomalies are usually short-lived and local to regional in scale.<ref name="cohen">Cohen, J., and D. Rind, 1991: The effect of snow cover on the climate. J. Climate, 4, 689–706.</ref> In some areas of the world such as [[Eurasia]], however, the cooling associated with a heavy snowpack and moist spring soils is known to play a role in modulating the summer [[monsoon]] circulation.<ref name="vernekar">Vernekar, A. D., J. Zhou, and J. Shukla, 1995: The effect of Eurasian snow cover on the Indian monsoon. J. Climate, 8, 248–266.</ref>

=== Climate change feedback mechanisms ===
{{Main|Climate change feedback}}
There are numerous cryosphere-climate feedbacks in the [[global climate]] system. These operate over a wide range of spatial and temporal scales from local seasonal cooling of air temperatures to hemispheric-scale variations in ice sheets over time scales of thousands of years. The feedback mechanisms involved are often complex and incompletely understood. For example, Curry ''et al.'' (1995) showed that the so-called "simple" sea ice-albedo feedback involved complex interactions with lead fraction, melt ponds, ice thickness, snow cover, and sea-ice extent.<ref>{{Cite journal |last1=Curry |first1=Judith A. |last2=Schramm |first2=Julie L. |last3=Ebert |first3=Elizabeth E. |date=1995 |title=Sea Ice-Albedo Climate Feedback Mechanism |journal=Journal of Climate |language=en |volume=8 |issue=2 |pages=240–247 |doi=10.1175/1520-0442(1995)008<0240:SIACFM>2.0.CO;2 |issn=0894-8755|doi-access=free |bibcode=1995JCli....8..240C }}</ref>

The role of snow cover in modulating the monsoon is just one example of a short-term cryosphere-climate feedback involving the land surface and the atmosphere.<ref name="vernekar" />{{citation needed|date=September 2023}}

== Components ==

=== Glaciers and ice sheets ===
{{Main|Glacier|Ice sheet}}
[[File:1249 Finsteraarhorn.jpg|thumb|Representation of glaciers on a [[National Maps of Switzerland|topographic map]]]]
[[File:Wildspitze_seen_from_Hinterer_Brunnkogel,_with_visible_ascent_track_of_ski_mountaineer.jpg|thumb|The Taschachferner [[glacier]] in the [[Ötztal Alps]] in [[Austria]]. The mountain to the left is the [[Wildspitze]] (3.768 m), second highest in Austria. To the right is an area with open [[crevasse]]s where the glacier flows over a kind of large [[cliff]].<ref>[https://www.google.com/maps/dir/Wildspitze,+6458,+%C3%96sterreich/Hinterer+Brochkogel,+6458,+%C3%96sterreich/@46.8693351,10.8649167,14z/data=!3m1!4b1!4m14!4m13!1m5!1m1!1s0x4782d399aa449a3b:0xc81bf75a6575685b!2m2!1d10.8672595!2d46.8854289!1m5!1m1!1s0x4782d388c6e336af:0xa4fff85a8397f10c!2m2!1d10.85!2d46.8833333!3e0 Google Maps: Distance between Wildspitze and Hinterer Brochkogel], cf. image scale at lower edge of screen</ref>]]

[[Ice sheet]]s and [[glacier]]s are flowing ice masses that rest on solid land. They are controlled by snow accumulation, surface and basal melt, calving into surrounding oceans or lakes and internal dynamics. The latter results from gravity-driven creep flow ("[[Ice flow dynamics|glacial flow]]") within the ice body and sliding on the underlying land, which leads to thinning and horizontal spreading.<ref name="GreveBlatter2009">{{cite book |author1=Greve, R. |title=Dynamics of Ice Sheets and Glaciers |author2=Blatter, H. |publisher=Springer |year=2009 |isbn=978-3-642-03414-5 |doi=10.1007/978-3-642-03415-2}}</ref> Any imbalance of this dynamic equilibrium between mass gain, loss and transport due to flow results in either growing or shrinking ice bodies.[[File:Greenland-ice_sheet_hg.jpg|thumb|Aerial view of the [[ice sheet]] on [[Greenland]]'s east coast]]Relationships between global climate and changes in ice extent are complex. The mass balance of land-based glaciers and ice sheets is determined by the accumulation of snow, mostly in winter, and warm-season [[ablation]] due primarily to net radiation and turbulent heat fluxes to melting ice and snow from warm-air advection<ref name="paterson">
Paterson, W. S. B., 1993: World sea level and the present mass balance of the Antarctic ice sheet. In: W.R. Peltier (ed.), Ice in the Climate System, NATO ASI Series, I12, Springer-Verlag, Berlin, 131–140.</ref><ref name="vandenbroeke">
Van den Broeke, M. R., 1996: The atmospheric boundary layer over ice sheets and glaciers. Utrecht, Universitiet Utrecht, 178 pp.</ref> Where ice masses terminate in the [[ocean]], iceberg [[Ice calving|calving]] is the major contributor to mass loss. In this situation, the ice margin may extend out into deep water as a floating [[ice shelf]], such as that in the [[Ross Sea]].

{{excerpt|glacier|paragraphs=1-3|file=no}}

{{excerpt|ice sheet|file=no}}
=== Sea ice ===
{{Main|Sea ice}}
[[File:Arctic ice.jpg|thumb|Broken pieces of Arctic sea ice with a snow cover]]
[[File:Seaice.jpg|thumb|Satellite image of sea ice forming near [[St. Matthew Island]] in the Bering Sea]]
[[Sea ice]] covers much of the polar oceans and forms by freezing of sea water. [[Satellite]] data since the early 1970s reveal considerable seasonal, regional, and interannual variability in the sea ice covers of both hemispheres. Seasonally, sea-ice extent in the [[Southern Hemisphere]] varies by a factor of 5, from a minimum of 3–4 million km<sup>2</sup> in February to a maximum of 17–20 million km<sup>2</sup> in September.<ref name="zwally">Zwally, H. J., J. C. Comiso, C. L. Parkinson, W. J. Campbell, F. D. Carsey, and P. Gloersen, 1983: Antarctic Sea Ice, 1973–1976: Satellite Passive-Microwave Observations. NASA SP-459, National Aeronautics and Space Administration, Washington, D.C., 206 pp.</ref><ref name="gloersen">Gloersen, P., W. J. Campbell, D. J. Cavalieri, J. C. Comiso, C. L. Parkinson, and H. J. Zwally, 1992: Arctic and Antarctic Sea Ice, 1978–1987: Satellite Passive-Microwave Observations and Analysis. NASA SP-511, National Aeronautics and Space Administration, Washington, D.C., 290 pp.</ref> The seasonal variation is much less in the Northern Hemisphere where the confined nature and high latitudes of the [[Arctic Ocean]] result in a much larger perennial ice cover, and the surrounding land limits the equatorward extent of wintertime ice. Thus, the seasonal variability in [[Northern Hemisphere]] ice extent varies by only a factor of 2, from a minimum of 7–9 million km<sup>2</sup> in September to a maximum of 14–16 million km<sup>2</sup> in March.<ref name="gloersen" /><ref name="parkinson">Parkinson, C. L., J. C. Comiso, H. J. Zwally, D. J. Cavalieri, P. Gloersen, and W. J. Campbell, 1987: Arctic Sea Ice, 1973–1976: Satellite Passive-Microwave Observations, NASA SP-489, National Aeronautics and Space Administration, Washington, D.C., 296 pp.</ref>

The ice cover exhibits much greater regional-scale interannual variability than it does hemispherical. For instance, in the region of the [[Sea of Okhotsk]] and [[Japan]], maximum ice extent decreased from 1.3 million km<sup>2</sup> in 1983 to 0.85 million km<sup>2</sup> in 1984, a decrease of 35%, before rebounding the following year to 1.2 million km<sup>2</sup>.<ref name="gloersen" /> The regional fluctuations in both hemispheres are such that for any several-year period of the [[satellite]] record some regions exhibit decreasing ice coverage while others exhibit increasing ice cover.<ref name="parkinson1995">Parkinson, C. L., 1995: Recent sea-ice advances in Baffin Bay/Davis Strait and retreats in the Bellinshausen Sea. Annals of Glaciology, 21, 348–352.</ref>

=== Frozen ground and permafrost ===
{{excerpt|permafrost|paragraphs=1-3}}

=== Snow cover ===
{{Main|Snow}}
[[File:Snow-covered_fir_trees.jpg|thumb|Snow-covered trees in [[Kuusamo]], [[Finland]]]]
[[File:Long Mynd snowdrift.jpeg|right|thumb|Snow drifts forming around downwind obstructions]]
Most of the Earth's snow-covered area is located in the [[Northern Hemisphere]], and varies seasonally from 46.5 million km<sup>2</sup> in January to 3.8 million km<sup>2</sup> in August.<ref name="robinson">Robinson, D. A., K. F. Dewey, and R. R. Heim, 1993: Global snow cover monitoring: an update. Bull. Amer. Meteorol. Soc., 74, 1689–1696.</ref>

[[Snow]] cover is an extremely important storage component in the water balance, especially seasonal [[snowpack]]s in mountainous areas of the world. Though limited in extent, seasonal [[snowpack]]s in the [[Earth]]'s mountain ranges account for the major source of the runoff for stream flow and [[groundwater]] recharge over wide areas of the midlatitudes. For example, over 85% of the annual runoff from the [[Colorado River]] basin originates as snowmelt. [[Snowmelt]] runoff from the Earth's mountains fills the rivers and recharges the aquifers that over a billion people depend on for their water resources.{{citation needed|date=September 2023}}

Furthermore, over 40% of the world's protected areas are in mountains, attesting to their value both as unique [[ecosystem]]s needing protection and as recreation areas for humans.{{citation needed|date=September 2023}}

=== Ice on lakes and rivers ===
{{See also|Ice#On lakes|Ice#On rivers and streams}}
[[Ice]] forms on [[river]]s and [[lake]]s in response to seasonal cooling. The sizes of the ice bodies involved are too small to exert anything other than localized climatic effects. However, the freeze-up/break-up processes respond to large-scale and local weather factors, such that considerable interannual variability exists in the dates of appearance and disappearance of the ice. Long series of lake-ice observations can serve as a proxy climate record, and the monitoring of freeze-up and break-up trends may provide a convenient integrated and seasonally-specific index of climatic perturbations. Information on river-ice conditions is less useful as a climatic proxy because ice formation is strongly dependent on river-flow regime, which is affected by precipitation, snow melt, and watershed runoff as well as being subject to human interference that directly modifies channel flow, or that indirectly affects the runoff via land-use practices.{{citation needed|date=September 2023}}

Lake freeze-up depends on the heat storage in the lake and therefore on its depth, the rate and temperature of any [[inflow (hydrology)|inflow]], and water-air energy fluxes. Information on lake depth is often unavailable, although some indication of the depth of shallow lakes in the [[Arctic]] can be obtained from airborne [[radar imagery]] during late winter (Sellman ''et al.'' 1975) and spaceborne optical imagery during summer (Duguay and Lafleur 1997). The timing of breakup is modified by snow depth on the ice as well as by ice thickness and freshwater inflow.{{citation needed|date=September 2023}}

==Changes caused by climate change==
{{excerpt|Effects of climate change#Ice and snow|file=no}}

===Ice sheet melt===
[[File:Beckmann 2023 Greenland 2300 RCP85 extent.png|thumb|2023 projections of how much the Greenland ice sheet may shrink from its present extent by the year 2300 under the worst possible climate change scenario (upper half) and of how much faster its remaining ice will be flowing in that case (lower half)<ref name="Beckmann2023">{{Cite journal |last1=Beckmann |first1=Johanna |last2=Winkelmann |first2=Ricarda |date=27 July 2023 |title=Effects of extreme melt events on ice flow and sea level rise of the Greenland Ice Sheet |journal=The Cryosphere |language=en |volume=17 |issue=7 |pages=3083–3099 |bibcode=2023TCry...17.3083B |doi=10.5194/tc-17-3083-2023 |doi-access=free}}</ref>]]

{{excerpt|Greenland ice sheet|paragraph=1,4,5,6|files=no}}

{{excerpt|Climate change in Antarctica|paragraph=4|files=no}}

===Decline of glaciers===
{{excerpt|Retreat of glaciers since 1850|paragraphs=1-2}}

===Sea ice decline===
{{excerpt|Effects of climate change#Sea ice decline}}

===Permafrost thaw===
{{excerpt|Permafrost#Impacts of climate change}}

=== Snow cover decrease ===
[[File:Duration of the yearly snow cover ring-width reconstruction together with modelled record for the Alps.webp|thumb|upright=1.35|Shrinkage of snow cover duration in the [[Alps]], starting ca. end of the 19th century, highlighting [[climate change adaptation]] needs<ref>{{cite journal |last1=Carrer |first1=Marco |last2=Dibona |first2=Raffaella |last3=Prendin |first3=Angela Luisa |last4=Brunetti |first4=Michele |title=Recent waning snowpack in the Alps is unprecedented in the last six centuries |journal=Nature Climate Change |date=February 2023 |volume=13 |issue=2 |pages=155–160 |doi=10.1038/s41558-022-01575-3 |bibcode=2023NatCC..13..155C |language=en |issn=1758-6798|doi-access=free|hdl=11577/3477269 |hdl-access=free }}</ref>]]
Studies in 2021 found that Northern Hemisphere snow cover has been decreasing since 1978, along with snow depth.<ref name=":AR6">{{Cite journal |last1=Fox-Kemper |first1=B. |last2=Hewitt |first2=H.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. |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. |title=Ocean, Cryosphere and Sea Level Change |url=https://www.vliz.be/imisdocs/publications/84/371584.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, Cambridge, UK and New York, NY, USA |volume=2021 |pages=1283–1285 |bibcode=<!-- not 2021AGUFM.U13B..09F --> |doi=10.1017/9781009157896.011 |isbn=9781009157896}}</ref> [[Paleoclimatology|Paleoclimate]] observations show that such changes are unprecedented over the last millennia in Western North America.<ref>{{Cite journal |last1=Pederson |first1=Gregory T. |last2=Gray |first2=Stephen T. |last3=Woodhouse |first3=Connie A. |author-link3=Connie Woodhouse |last4=Betancourt |first4=Julio L. |last5=Fagre |first5=Daniel B. |last6=Littell |first6=Jeremy S. |last7=Watson |first7=Emma |last8=Luckman |first8=Brian H. |last9=Graumlich |first9=Lisa J. |date=2011-07-15 |title=The Unusual Nature of Recent Snowpack Declines in the North American Cordillera |url=https://www.science.org/doi/10.1126/science.1201570 |journal=Science |language=en |volume=333 |issue=6040 |pages=332–335 |bibcode=2011Sci...333..332P |doi=10.1126/science.1201570 |issn=0036-8075 |pmid=21659569 |s2cid=29486298}}</ref><ref>{{Cite journal |last1=Belmecheri |first1=Soumaya |last2=Babst |first2=Flurin |last3=Wahl |first3=Eugene R. |last4=Stahle |first4=David W. |last5=Trouet |first5=Valerie |date=2016 |title=Multi-century evaluation of Sierra Nevada snowpack |url=https://www.nature.com/articles/nclimate2809 |journal=Nature Climate Change |language=en |volume=6 |issue=1 |pages=2–3 |bibcode=2016NatCC...6....2B |doi=10.1038/nclimate2809 |issn=1758-6798}}</ref><ref name=":AR6" />

[[North America]]n winter snow cover increased during the 20th century,<ref>{{Cite journal |last1=Brown |first1=Ross D. |last2=Goodison |first2=Barry E. |last3=Brown |first3=Ross D. |last4=Goodison |first4=Barry E. |date=1996-06-01 |title=Interannual Variability in Reconstructed Canadian Snow Cover, 1915–1992 |journal=Journal of Climate |language=EN |volume=9 |issue=6 |pages=1299–1318 |bibcode=1996JCli....9.1299B |doi=10.1175/1520-0442(1996)009<1299:ivircs>2.0.co;2 |doi-access=free}}</ref><ref>{{Cite book |last1=Hughes |first1=M. G. |title=Proceedings of the Annual Meeting - Eastern Snow Conference |last2=Frei |first2=A. |last3=Robinson |first3=D.A. |date=1996 |publisher=Eastern Snow Conference |isbn=9780920081181 |location=Williamsburg, Virginia |pages=21–31 |language=en |chapter=Historical analysis of North American snow cover extent: merging satellite and station-derived snow cover observations |chapter-url=https://books.google.com/books?id=PassAQAAMAAJ}}</ref> largely in response to an increase in precipitation.<ref name="groisman94">Groisman, P. Ya, and D. R. Easterling, 1994: Variability and trends of total precipitation and snowfall over the United States and Canada. J. Climate, 7, 184–205.</ref>

Because of its close relationship with hemispheric air temperature, snow cover is an important indicator of climate change.{{citation needed|date=September 2023}}

Global warming is expected to result in major changes to the partitioning of snow and rainfall, and to the timing of snowmelt, which will have important implications for water use and management.{{citation needed|date=September 2023}} These changes also involve potentially important decadal and longer time-scale [[feedback]]s to the climate system through temporal and spatial changes in [[soil moisture]] and runoff to the [[ocean]]s.(Walsh 1995). Freshwater fluxes from the snow cover into the marine environment may be important, as the total flux is probably of the same magnitude as desalinated ridging and rubble areas of sea ice.<ref name="prinsenberg">Prinsenberg, S. J. 1988: Ice-cover and ice-ridge contributions to the freshwater contents of Hudson Bay and Foxe Basin. Arctic, 41, 6–11.</ref> In addition, there is an associated pulse of precipitated pollutants which accumulate over the Arctic winter in snowfall and are released into the ocean upon [[ablation]] of the [[sea ice]].{{citation needed|date=September 2023}}

==See also==
* [[Cryobiology]]
* [[International Association of Cryospheric Sciences]] (IACS)
* [[Polar regions of Earth]]
* [[Special Report on the Ocean and Cryosphere in a Changing Climate]]
* [[Water cycle]]

== References ==
{{Reflist}}

==External links==
{{Commons category}}
* [https://www.ccin.ca/ Canadian Cryospheric Information Network]
* [https://web.archive.org/web/20050617080315/http://nsidc.org/cryosphere/glance/ Near-real-time overview of global ice concentration and snow extent]
* [https://nsidc.org/ National Snow and Ice Data Center]

{{climate change}}
{{Authority control}}

[[Category:Cryosphere| ]]
[[Category:Water ice]]