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{{Short description|Soil frozen for a duration of at least two years}}
{{About|frozen ground}}
{{Good article}}
{{Use dmy dates|date=January 2022}}
{{Infobox soil
|name=Permafrost
|alternative_name= 
|image= Circum-Arctic Map of Permafrost and Ground Ice Conditions.png
|image_size=250px
|image_caption= Extent and types of permafrost in the [[Northern Hemisphere]]
|classification_system=[[International Permafrost Association]]
|code=
|profile=
|process=
|parent_material=
|climate= High latitudes, alpine regions
}}

'''Permafrost''' ({{etymology||{{wikt-lang|en|perma-}}|[[clipping (morphology)|permanent]]||[[frost]]}}) is [[soil]] or underwater [[sediment]] which continuously remains below {{cvt|0|C|F}} for two years or more: the oldest permafrost had been continuously frozen for around 700,000 years.<ref name="MIT2022">{{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> Whilst the shallowest permafrost has a vertical extent of below a meter (3&nbsp;ft), the deepest is greater than {{convert|1500|m|ft|abbr=on}}.<ref name="IPADefinition" /> Similarly, the area of individual permafrost zones may be limited to narrow mountain [[summit]]s or extend across vast [[Arctic]] regions.<ref name="NRDC">{{cite web |url=https://nrdc.org/stories/permafrost-everything-you-need-know |last=Denchak|first=Melissa |title=Permafrost: Everything You Need to Know |date=26 June 2018 |publisher=[[Natural Resources Defense Council]] |access-date=27 September 2023 }}</ref> The ground beneath [[glacier]]s and [[ice sheet]]s is not usually defined as permafrost, so on land, permafrost is generally located beneath a so-called [[active layer]] of soil which freezes and thaws depending on the season.<ref name="Cooper2023">{{cite journal |last1=Cooper |first1=M. G. |last2=Zhou |first2=T. |last3=Bennett |first3=K. E. |last4=Bolton |first4=W. R. |last5=Coon |first5=E. T. |last6=Fleming |first6=S. W. |last7=Rowland |first7=J. C. |last8=Schwenk |first8=J. |date=4 January 2023 |title=Detecting Permafrost Active Layer Thickness Change From Nonlinear Baseflow Recession |journal=Water Resources Research |volume=57 |issue=1 |pages=e2022WR033154 |doi=10.1029/2022WR033154 |bibcode=2023WRR....5933154C |s2cid=255639677 }}</ref>

Around 15% of the [[Northern Hemisphere]] or 11% of the global surface is underlain by permafrost,<ref name="Obu2021">{{cite journal |last=Obu|first=J. |date=2021 |title=How Much of the Earth's Surface is Underlain by Permafrost? |journal=Journal of Geophysical Research: Earth Surface |volume=126 |issue=5 |pages=e2021JF006123 |doi=10.1029/2021JF006123 |bibcode=2021JGRF..12606123O |doi-access=free}}</ref> covering a total area of around {{convert|18|e6km2|e6sqmi|abbr=unit}}.<ref name="Sayedi2020">{{cite journal |last1=Sayedi |first1=Sayedeh Sara |last2=Abbott |first2=Benjamin W |last3=Thornton |first3=Brett F |last4=Frederick |first4=Jennifer M |last5=Vonk |first5=Jorien E |last6=Overduin |first6=Paul |last7=Schädel |first7=Christina |last8=Schuur |first8=Edward A G |last9=Bourbonnais |first9=Annie |last10=Demidov |first10=Nikita |last11=Gavrilov |first11=Anatoly |date=22 December 2020 |title=Subsea permafrost carbon stocks and climate change sensitivity estimated by expert assessment |journal=[[Environmental Research Letters]] |volume=15 |issue=12 |pages=B027-08 |doi=10.1088/1748-9326/abcc29 |bibcode=2020AGUFMB027...08S |s2cid=234515282 |doi-access=free}}</ref> This includes large areas of [[Alaska]], [[Canada]], [[Greenland]], and [[Siberia]]. It is also located in high mountain regions, with the [[Tibetan Plateau]] being a prominent example. Only a minority of permafrost exists in the [[Southern Hemisphere]], where it is consigned to mountain slopes like in the [[Andes]] of [[Patagonia]], the [[Southern Alps]] of New Zealand, or the highest mountains of [[Antarctica]].<ref name="NRDC" /><ref name="MIT2022" />

Permafrost contains large amounts of dead [[biomass]] that have accumulated throughout millennia without having had the chance to fully decompose and release their [[carbon]], making [[tundra]] soil a [[carbon sink]].<ref name="NRDC" /> As [[climate change|global warming]] heats the ecosystem, frozen soil thaws and becomes warm enough for decomposition to start anew, accelerating the [[permafrost carbon cycle]]. Depending on conditions at the time of thaw, decomposition can release either [[carbon dioxide]] or [[methane]], and these [[greenhouse gas emissions]] act as a [[climate change feedback]].<ref name="NOAA">{{cite web |url=https://arctic.noaa.gov/Report-Card/Report-Card-2019/ArtMID/7916/ArticleID/844/Permafrost-and-the-Global-Carbon-Cycle |last=Schuur|first=T. |title=Permafrost and the Global Carbon Cycle |date=November 22, 2019 |publisher=[[Natural Resources Defense Council]] |via=[[NOAA]]}}</ref><ref>{{cite journal |last1=Koven |first1=Charles D. |last2=Ringeval |first2=Bruno |last3=Friedlingstein |first3=Pierre |last4=Ciais |first4=Philippe |last5=Cadule |first5=Patricia |last6=Khvorostyanov |first6=Dmitry |last7=Krinner |first7=Gerhard |last8=Tarnocai |first8=Charles |title=Permafrost carbon-climate feedbacks accelerate global warming |journal=[[Proceedings of the National Academy of Sciences]] |date=6 September 2011 |volume=108 |issue=36 |pages=14769–14774 |doi=10.1073/pnas.1103910108 |pmid=21852573 |pmc=3169129 |bibcode=2011PNAS..10814769K |doi-access=free }}</ref><ref>{{Cite journal |last1=Galera |first1=L. A. |last2=Eckhardt |first2=T. |last3=Beer C. |first3=Pfeiffer E.-M. |last4=Knoblauch |first4=C. |date=22 March 2023 |title=Ratio of in situ CO2 to CH4 production and its environmental controls in polygonal tundra soils of Samoylov Island, Northeastern Siberia |journal=Journal of Geophysical Research: Biogeosciences |volume=128 |issue=4 |page=e2022JG006956 |doi=10.1029/2022JG006956|bibcode=2023JGRG..12806956G |s2cid=257700504 |doi-access=free }}</ref> The emissions from thawing permafrost will have a sufficient impact on the climate to impact global [[carbon budget]]s. It is difficult to accurately predict how much greenhouse gases the permafrost releases because of the different thaw processes are still uncertain. There is widespread agreement that the emissions will be smaller than human-caused emissions and not large enough to result in [[runaway greenhouse effect|runaway warming]].<ref name="AR6_WG1_Chapter92">Fox-Kemper, B., H.T. Hewitt, C. Xiao, G. Aðalgeirsdóttir, S.S. Drijfhout, T.L. Edwards, N.R. Golledge, M. Hemer, R.E. Kopp, G. Krinner, A. Mix, D. Notz, S. Nowicki, I.S. Nurhati, L. Ruiz, J.-B. Sallée, A.B.A. Slangen, and Y. Yu, 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter09.pdf Chapter 9: Ocean, Cryosphere and Sea Level Change]. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1211–1362.</ref> Instead, the annual permafrost emissions are likely comparable with global emissions from [[deforestation]], or to annual emissions of large countries such as [[Greenhouse gas emissions by Russia|Russia]], the [[Greenhouse gas emissions by the United States|United States]] or [[Greenhouse gas emissions by China|China]].<ref name="Schuur2022">{{Cite journal |last1=Schuur |first1=Edward A.G. |last2=Abbott |first2=Benjamin W. |last3=Commane |first3=Roisin |last4=Ernakovich |first4=Jessica |last5=Euskirchen |first5=Eugenie |last6=Hugelius |first6=Gustaf |last7=Grosse |first7=Guido |last8=Jones |first8=Miriam |last9=Koven |first9=Charlie |last10=Leshyk |first10=Victor |last11=Lawrence |first11=David |last12=Loranty |first12=Michael M. |last13=Mauritz |first13=Marguerite |last14=Olefeldt |first14=David |last15=Natali |first15=Susan |year=2022 |title=Permafrost and Climate Change: Carbon Cycle Feedbacks From the Warming Arctic |journal=Annual Review of Environment and Resources |volume=47 |pages=343–371 |doi=10.1146/annurev-environ-012220-011847 |s2cid=252986002 |last16=Rodenhizer |first16=Heidi |last17=Salmon |first17=Verity |last18=Schädel |first18=Christina |last19=Strauss |first19=Jens |last20=Treat |first20=Claire |last21=Turetsky |first21=Merritt}}</ref>

In addition to its climate impact, permafrost thaw brings additional risks. Formerly frozen ground often contains enough ice that when it thaws, [[Phreatic zone|hydraulic saturation]] is suddenly exceeded, so the ground shifts substantially and may even collapse outright. Many buildings and other infrastructure were built on permafrost when it was frozen and stable, and so are vulnerable to collapse if it thaws.<ref name="Nelson2002" /> Estimates suggest nearly 70% of such infrastructure is at risk by 2050, and that the associated costs could rise to tens of billions of dollars in the second half of the century.<ref name="Hjort2022" /> Furthermore, between 13,000 and 20,000 sites contaminated with [[toxic waste]] are present in the permafrost,<ref name="Langer2023" /> as well as the natural [[mercury (element)|mercury]] deposits,<ref name="Schaefer2020" /> which are all liable to leak and pollute the environment as the warming progresses.<ref name="Miner2021" /> Lastly, concerns have been raised about the potential for [[Pathogenic microorganisms in frozen environments|pathogenic microorganisms surviving the thaw]] and contributing to future [[pandemic]]s.<ref name="Alempic2023" /><ref name="Alund2023" /> However, the scientific consensus is that this particular risk is speculative and implausible.<ref name="Yong2014" /><ref name="Doucleff2020" /><ref name="Wu2022" />

== Classification and extent ==
[[File:Vertical Temperature Profile in Permafrost (English Text).jpg|thumb|upright=1.3|Permafrost temperature profile. Permafrost occupies the middle zone, with the active layer above it, while [[geothermal activity]] keeps the lowest layer above freezing. The vertical {{convert|0|°C|disp=or}} line denotes the average annual temperature that is crucial for the upper and lower limit of the permafrost zone, while the red lines represent seasonal temperature changes and seasonal temperature extremes. Solid curved lines at the top show seasonal maximum and minimum temperatures in the active layer, while the red dotted-to-solid line depicts the average temperature profile with depth of soil in a permafrost region.]]
Permafrost is [[soil]], [[Rock (geology)|rock]] or [[sediment]] that is frozen for more than two consecutive years. In practice, this means that permafrost occurs at a mean annual temperature of {{convert|−2|°C|1}} or below. In the coldest regions, the depth of continuous permafrost can exceed {{convert|1400|m|ft|abbr=on}}.<ref name="Desonie2008" /> It typically exists beneath the so-called [[active layer]], which freezes and thaws annually, and so can support plant growth, as the [[root]]s can only take hold in the soil that's thawed.<ref name="IPADefinition" /> Active layer thickness is measured during its maximum extent at the end of summer:<ref>{{cite journal |last1=Zhang |first1=Caiyun |last2=Douglas |first2=Thomas A. |last3=Anderson |first3=John E. |title=Modeling and mapping permafrost active layer thickness using field measurements and remote sensing techniques |journal=International Journal of Applied Earth Observation and Geoinformation |date=27 July 2021 |volume=102 |doi=10.1016/j.jag.2021.102455 |bibcode=2021IJAEO.10202455Z }}</ref> as of 2018, the average thickness in the [[Northern Hemisphere]] is ~{{convert|145|cm|ft}}, but there are significant regional differences. Northeastern [[Siberia]], [[Alaska]] and [[Greenland]] have the most solid permafrost with the lowest extent of active layer (less than {{convert|50|cm|ft}} on average, and sometimes only {{convert|30|cm|ft}}), while southern [[Norway]] and the [[Mongolian Plateau]] are the only areas where the average active layer is deeper than {{convert|600|cm|ft}}, with the record of {{convert|10|m|ft}}.<ref name="Li2022">{{cite journal |last1=Li |first1=Chuanhua |last2=Wei |first2=Yufei |last3=Liu |first3=Yunfan |last4=Li |first4=Liangliang |last5=Peng |first5=Lixiao |last6=Chen |first6=Jiahao |last7=Liu |first7=Lihui |last8=Dou |first8=Tianbao |last9=Wu |first9=Xiaodong |date=14 June 2022 |title=Active Layer Thickness in the Northern Hemisphere: Changes From 2000 to 2018 and Future Simulations |journal=JGR Atmospheres |volume=127 |issue=12 |pages=e2022JD036785 |doi=10.1029/2022JD036785 |bibcode=2022JGRD..12736785L |s2cid=249696017 }}</ref><ref>{{cite journal |last1=Luo |first1=Dongliang |last2=Wu |first2=Qingbai |last3=Jin |first3=Huijun |last4=Marchenko |first4=Sergey S. |last5=Lü |first5=Lanzhi |last6=Gao |first6=Siru |title=Recent changes in the active layer thickness across the northern hemisphere |journal=Environmental Earth Sciences |date=26 March 2016 |volume=75 |issue=7 |page=555 |doi=10.1007/s12665-015-5229-2 |bibcode=2016EES....75..555L |s2cid=130353989 }}</ref> The border between active layer and permafrost itself is sometimes called permafrost table.<ref name="Lacelle2022" />

Around 15% of [[Northern Hemisphere]] land that is not completely covered by ice is directly underlain by permafrost; 22% is defined as part of a permafrost zone or region.<ref name="Obu2021" /> This is because only slightly more than half of this area is defined as a continuous permafrost zone, where 90%–100% of the land is underlain by permafrost. Around 20% is instead defined as discontinuous permafrost, where the coverage is between 50% and 90%. Finally, the remaining <30% of permafrost regions consists of areas with 10%–50% coverage, which are defined as sporadic permafrost zones, and some areas that have isolated patches of permafrost covering 10% or less of their area.<ref name="Brown1997">{{cite report |last1=Brown |first1=J. |last2=Ferrians Jr. |first2=O. J. |last3=Heginbottom |first3=J. A. |last4=Melnikov |first4=E. S. |title=Circum-Arctic map of permafrost and ground-ice conditions |year=1997 |publisher=[[USGS]] |doi=10.3133/cp45 |doi-access=free }}</ref><ref>{{cite report |last1=Heginbottom |first1=J. Alan |last2=Brown |first2=Jerry |last3=Humlum |first3=Ole |last4=Svensson |first4=Harald |title=State of the Earth's Cryosphere at the Beginning of the 21st Century: Glaciers, Global Snow Cover, Floating Ice, and Permafrost and Periglacial Environments |year=2012 |publisher=[[USGS]] |url=https://pubs.usgs.gov/pp/p1386a/pdf/pp1386a-5-web.pdf |doi=10.3133/pp1386A }}</ref>{{rp|435}} Most of this area is found in Siberia, northern Canada, Alaska and Greenland. Beneath the active layer annual temperature swings of permafrost become smaller with depth. The greatest depth of permafrost occurs right before the point where geothermal heat maintains a temperature above freezing. Above that bottom limit there may be permafrost with a consistent annual temperature—"isothermal permafrost".<ref name="Degradation">{{cite journal|last=Delisle |first=G. |title=Near-surface permafrost degradation: How severe during the 21st century? |journal=Geophysical Research Letters |volume=34 |issue=L09503 |pages=4 |date=10 May 2007 |doi=10.1029/2007GL029323 |bibcode=2007GeoRL..34.9503D| doi-access=free }}</ref>

=== Continuity of coverage ===
Permafrost typically forms in any [[climate]] where the mean annual air temperature is lower than the freezing point of water. Exceptions are found in [[taiga|humid boreal forests]], such as in Northern [[Scandinavia]] and the North-Eastern part of [[European Russia]] west of the [[Ural Mountains|Urals]], where snow acts as an insulating blanket. Glaciated areas may also be exceptions. Since all glaciers are warmed at their base by geothermal heat, [[Glacier#Types|temperate glaciers]], which are near the [[pressure melting point]] throughout, may have liquid water at the interface with the ground and are therefore free of underlying permafrost.<ref>{{cite book |last=Sharp |first=Robert Phillip |author-link=Robert P. Sharp |title=Living Ice: Understanding Glaciers and Glaciation |publisher=Cambridge University Press |page=[https://archive.org/details/livingiceunderst0000shar/page/27 27] |url=https://archive.org/details/livingiceunderst0000shar |url-access=registration |isbn=978-0-521-33009-1 |date=1988 }}</ref> "Fossil" cold anomalies in the [[geothermal gradient]] in areas where deep permafrost developed during the Pleistocene persist down to several hundred metres. This is evident from temperature measurements in [[borehole]]s in North America and Europe.<ref>{{Cite journal |last=Majorowicz |first=Jacek |title=Permafrost at the ice base of recent pleistocene glaciations – Inferences from borehole temperatures profiles |journal=Bulletin of Geography. Physical Geography Series |series=Physical Geography Series |date=28 December 2012 |doi=10.2478/v10250-012-0001-x |volume=5 |pages=7–28 |doi-access = free }}</ref>

==== Discontinuous permafrost ====
[[File:Digging in permafrost.jpg|thumb|left|Excavating ice-rich permafrost with a [[jackhammer]] in [[Alaska]].]]
The below-ground temperature varies less from season to season than the air temperature, with mean annual temperatures tending to increase with depth as a result of the geothermal crustal gradient. Thus, if the mean annual air temperature is only slightly below {{convert|0|°C|°F|abbr=on}}, permafrost will form only in spots that are sheltered (usually with a northern or southern [[aspect (geography)|aspect]], in north and south hemispheres respectively) creating discontinuous permafrost. Usually, permafrost will remain discontinuous in a climate where the mean annual soil surface temperature is between {{convert|-5|and|0|C|F}}. In the moist-wintered areas mentioned before, there may not be even discontinuous permafrost down to {{convert|-2|°C|°F}}. Discontinuous permafrost is often further divided into extensive discontinuous permafrost, where permafrost covers between 50 and 90 percent of the landscape and is usually found in areas with mean annual temperatures between {{convert|-2|and|-4|C|F}}, and sporadic permafrost, where permafrost cover is less than 50 percent of the landscape and typically occurs at mean annual temperatures between {{convert|0|and|-2|C|F}}.<ref name="BrownPéwé">{{Cite journal |last1=Brown |first1=Roger J.E. |last2=Péwé |first2=Troy L. |title=Distribution of permafrost in North America and its relationship to the environment: A review, 1963–1973 |journal=Permafrost: North American Contribution – Second International Conference |volume=2 |pages=71–100 |year=1973 |isbn=978-0-309-02115-9 |url=https://books.google.com/books?id=SjErAAAAYAAJ&pg=PA72}}</ref>

In soil science, the sporadic permafrost zone is abbreviated '''SPZ''' and the extensive discontinuous permafrost zone '''DPZ'''.<ref>{{Cite report |first= S.D. |last= Robinson |editor-last=Phillips |contribution= Permafrost and peatland [[carbon sink]] capacity with increasing latitude |title= Permafrost |year=2003 |pages=965–970 |publisher=Swets & Zeitlinger |url=http://www.arlis.org/docs/vol1/ICOP/55700698/Pdf/Chapter_169.pdf |isbn=90-5809-582-7 |display-authors=etal |display-editors=etal |access-date=18 August 2023 |archive-url=https://web.archive.org/web/20140302190815/http://www.arlis.org/docs/vol1/ICOP/55700698/Pdf/Chapter_169.pdf |archive-date=2 March 2014 |url-status=live }}</ref> Exceptions occur in un-glaciated [[Siberia]] and [[Alaska]] where the present depth of permafrost is a [[Relict (geology)|relic]] of climatic conditions during glacial ages where winters were up to {{convert|11|C-change}} colder than those of today.

==== Continuous permafrost ====
{| class="wikitable floatright"
|+ Estimated extent of alpine permafrost by region<ref name="BockhMunr" />
|-
! Locality
! Area 
|-
| [[Qinghai-Tibet Plateau]]
| style="text-align:right;" | {{convert|1300000|km2|mi2|abbr=on}}
|-
| [[Khangai Mountains|Khangai]]-[[Altai Mountains]]
| style="text-align:right;" | {{convert|1000000|km2|mi2|abbr=on}}
|-
| [[Brooks Range]]
| style="text-align:right;" | {{convert|263000|km2|mi2|abbr=on}}
|-
| [[Siberia#Mountain ranges|Siberian Mountains]]
| style="text-align:right;" | {{convert|255000|km2|mi2|abbr=on}}
|-
| [[Greenland]]
| style="text-align:right;" | {{convert|251000|km2|mi2|abbr=on}}
|-
| [[Ural Mountains]]
| style="text-align:right;" | {{convert|125000|km2|mi2|abbr=on}}
|-
| [[Andes]]
| style="text-align:right;" | {{convert|100000|km2|mi2|abbr=on}}
|-
| [[Rocky Mountains]] (US and Canada)
| style="text-align:right;" | {{convert|100000|km2|mi2|abbr=on}}
|-
| [[Alps]]
| style="text-align:right;" | {{convert|80000|km2|mi2|abbr=on}}
|-
| [[Fennoscandian]] mountains
| style="text-align:right;" | {{convert|75000|km2|mi2|abbr=on}}
|-
| Remaining
| style="text-align:right;" | <{{convert|50000|km2|mi2|abbr=on}}
|}
At mean annual soil surface temperatures below {{convert|-5|C}} the influence of aspect can never be sufficient to thaw permafrost and a zone of continuous permafrost (abbreviated to '''CPZ''') forms. A line of continuous permafrost in the [[Northern Hemisphere]]<ref>{{cite book |title=Frozen ground engineering |first1=Orlando B. |last1=Andersland |first2=Branko |last2=Ladanyi |publisher=Wiley |year=2004 |page=5 |isbn=978-0-471-61549-1 |edition=2nd}}</ref> represents the most southern border where land is covered by continuous permafrost or glacial ice. The line of continuous permafrost varies around the world northward or southward due to regional climatic changes. In the [[southern hemisphere]], most of the equivalent line would fall within the [[Southern Ocean]] if there were land there. Most of the [[Antarctica|Antarctic continent]] is overlain by glaciers, under which much of the terrain is subject to basal [[pressure melting point|melting]].<ref>{{Cite journal |last=Zoltikov |first=I.A. |title=Heat regime of the central Antarctic glacier |journal=Antarctica, Reports of the Commission, 1961 |pages=27–40 |year=1962 |language=ru }}</ref> The exposed land of Antarctica is substantially underlain with permafrost,<ref>{{Cite book |first1=Iain B. |last1=Campbell |first2=Graeme G. C. |last2=Claridge |editor-last=Margesin |editor-first=Rosa |contribution=Antarctic Permafrost Soils |isbn=978-3-540-69370-3 |title = Permafrost Soils |volume=16 |year=2009 |pages=17–31 |place = Berlin |publisher=Springer |doi=10.1007/978-3-540-69371-0_2 |series=Soil Biology }}</ref> some of which is subject to warming and thawing along the coastline.<ref>{{Cite news |last=Heinrich |first=Holly |title=Permafrost Melting Faster Than Expected in Antarctica |publisher=[[National Public Radio]] |date=25 July 2013 |url=https://stateimpact.npr.org/texas/2013/07/25/permafrost-melting-faster-than-expected-in-antarctica/ |access-date=23 April 2016 |archive-url=https://web.archive.org/web/20160503120018/https://stateimpact.npr.org/texas/2013/07/25/permafrost-melting-faster-than-expected-in-antarctica/ |archive-date=3 May 2016 |url-status=live }}</ref>

=== Alpine permafrost ===
A range of elevations in both the [[Northern Hemisphere|Northern]] and [[Southern Hemisphere]] are cold enough to support perennially frozen ground: some of the best-known examples include the [[Canadian Rockies]], the [[European Alps]], [[Himalaya]] and the [[Tien Shan]]. In general, it has been found that extensive alpine permafrost requires mean annual air temperature of {{cvt|-3|C|F}}, though this can vary depending on local [[topography]], and some mountain areas are known to support permafrost at {{cvt|-1|C|F}}. It is also possible for subsurface alpine permafrost to be covered by warmer, vegetation-supporting soil.<ref name="Haeberli2010">{{cite journal |last1=Haeberli |first1=Wilfried |last2=Noetzli |first2=Jeannette |last3=Arenson |first3=Lukas |last4=Delaloye |first4=Reynald |last5=Gärtner-Roer |first5=Isabelle |last6=Gruber |first6=Stephan |last7=Isaksen |first7=Ketil |last8=Kneisel |first8=Christof |last9=Krautblatter |first9=Michael |last10=Phillips |first10=Marcia |year=2010 |title=Mountain permafrost: development and challenges of a young research field |journal=Journal of Glaciology |volume=56 |issue=200 |pages=1043–1058 |publisher=Cambridge University Press |doi=10.3189/002214311796406121 |bibcode=2010JGlac..56.1043H |s2cid=33659636 }}</ref>
[[File:Sayedi 2020 post LGM permafrost.jpg|thumb|Changes in subsea permafrost extent and structure between the Last Glacial Maximum and now.<ref name="Sayedi2020" />]]
Alpine permafrost is particularly difficult to study, and systematic research efforts did not begin until the 1970s.<ref name="Haeberli2010" /> Consequently, there remain uncertainties about its geography. As recently as 2009, permafrost had been discovered in a new area – Africa's highest peak, [[Mount Kilimanjaro]] ({{Convert|4700|m|ft|abbr=on}} above sea level and approximately 3° south of the [[equator]]).<ref>{{Cite news |last=Rozell |first=Ned |title=Permafrost near equator; hummingbirds near subarctic |newspaper=Capitol City Weekly |place=Juneau, Alaska |date=18 November 2009 |url=http://www.capitalcityweekly.com/stories/111809/out_522300722.shtml| archive-url=https://web.archive.org/web/20180305063150/http://www.capitalcityweekly.com/stories/111809/out_522300722.shtml | archive-date=5 March 2018}}</ref> In 2014, a collection of regional estimates of alpine permafrost extent had established a global extent of {{convert|3560000|km2|mi2|abbr=on}}.<ref name=BockhMunr>{{cite journal |last1=Bockheim |first1=James G. |last2=Munroe |first2=Jeffrey S. |title=Organic Carbon Pools and Genesis of Alpine Soils with Permafrost: A Review |journal=Arctic, Antarctic, and Alpine Research |date=November 2014 |volume=46 |issue=4 |pages=987–1006 |doi=10.1657/1938-4246-46.4.987 |bibcode=2014AAAR...46..987B |s2cid=53400041 |doi-access=free }}</ref> Yet, by 2014, alpine permafrost in the [[Andes]] has not been fully mapped,<ref>{{cite thesis |last1=Azocar |first1=Guillermo |title=Modeling of Permafrost Distribution in the Semi-arid Chilean Andes |date=2 January 2014 |hdl=10012/8109 }}</ref> although its extent has been modeled to assess the amount of water bound up in these areas.<ref>{{Cite report |last1=Ruiz |first1= Lucas |last2=Liaudat |first2 =Dario Trombotto |title=Mountain Permafrost Distribution in the Andes of Chubut (Argentina) Based on a Statistical Model |place= Mendoza, Argentina |publisher=Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales |series=Tenth International Conference on Permafrost |year=2012 |pages=365–370 |url=http://www.geocriologia.com.ar/wp-content/uploads/2011/11/Pages-from-TICOP2012.pdf |access-date=24 April 2016 |archive-url =https://web.archive.org/web/20160513180525/http://www.geocriologia.com.ar/wp-content/uploads/2011/11/Pages-from-TICOP2012.pdf |archive-date=13 May 2016 |url-status=live }}</ref>

=== Subsea permafrost ===
Subsea permafrost occurs beneath the [[seabed]] and exists in the [[continental shelf|continental shelves]] of the polar regions.<ref name="IPADefinition">{{cite web |title=What is Permafrost? |url=https://www.permafrost.org/what-is-permafrost/ |access-date=27 September 2023 |publisher=International Permafrost Association}}</ref> These areas formed during the last [[Last Glacial Period|Ice Age]], when a larger portion of Earth's water was bound up in [[ice sheet]]s on land and when sea levels were low. As the ice sheets melted to again become seawater during the [[Holocene glacial retreat]], coastal permafrost became submerged shelves under relatively warm and salty boundary conditions, compared to surface permafrost. Since then, these conditions led to the gradual and ongoing decline of subsea permafrost extent.<ref name="Sayedi2020" /> Nevertheless, its presence remains an important consideration for the "design, construction, and operation of coastal facilities, structures founded on the seabed, [[artificial island]]s, [[submarine pipeline|sub-sea pipelines]], and [[oil well|wells]] drilled for [[mineral exploration|exploration]] and production".<ref name="Osterkamp2001">{{Cite book |last=Osterkamp |first=T. E. |chapter=Sub-Sea Permafrost |title=Encyclopedia of Ocean Sciences |pages=2902–12 |year=2001 |doi=10.1006/rwos.2001.0008 |isbn=978-0-12-227430-5 |chapter-url=https://archive.org/details/encyclopediaofoc0000unse }}</ref> Subsea permafrost can also overlay deposits of [[methane clathrate]], which were once speculated to be a major [[tipping points in the climate system|climate tipping point]] in what was known as a [[clathrate gun hypothesis]], but are now no longer believed to play any role in projected climate change.<ref name="IPCC AR6 WG1 Ch.5">{{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=Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks |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 |url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter05.pdf |publisher=Cambridge University Press, Cambridge, UK and New York, NY, USA |page=5 |doi=10.1017/9781009157896.011 |quote=It is very unlikely that gas clathrates (mostly methane) in deeper terrestrial permafrost and subsea clathrates will lead to a detectable departure from the emissions trajectory during this century. }}</ref>

=== Past extent of permafrost ===
At the [[Last Glacial Maximum]], continuous permafrost covered a much greater area than it does today, covering all of ice-free Europe south to about [[Szeged]] (southeastern [[Hungary]]) and the [[Sea of Azov]] (then dry land)<ref>{{cite journal |last1=Sidorchuk |first1=Aleksey |last2=Borisova |first2=Olga |last3=Panin |first3=Andrey |date=20 February 2001 |title=Fluvial response to the late Valdai/Holocene environmental change on the East European plain |url=http://www.fluvial-systems.net/present_en/global.pdf |archive-url=https://web.archive.org/web/20131226230314/http://www.fluvial-systems.net/present_en/global.pdf |archive-date=26 December 2013 |journal=Quaternary International |volume=118–119 |issue=1–4 |pages=13–22 |doi=10.1016/S0921-8181(00)00081-3 |bibcode=2001GPC....28..303S }}</ref> and East Asia south to present-day [[Changchun]] and [[Abashiri, Hokkaidō|Abashiri]].<ref>{{cite journal |last1=Ono |first1=Yugo |last2=Irino |first2=Tomohisa |date=16 September 2003 |title=Southern migration of westerlies in the Northern Hemisphere PEP II transect during the Last Glacial Maximum |journal=Quaternary International |volume=118–119 |pages=13–22 |doi=10.1016/S1040-6182(03)00128-9 }}</ref> In North America, only an extremely narrow belt of permafrost existed south of the [[ice sheet]] at about the latitude of [[New Jersey]] through southern [[Iowa]] and northern [[Missouri]], but permafrost was more extensive in the drier western regions where it extended to the southern border of [[Idaho]] and [[Oregon]].<ref>{{cite journal |last1=Malde |first1=Harold E. |date=1 March 1964 |title=Patterned Ground in the Western Snake River Plain, Idaho, and Its Possible Cold-Climate Origin |journal=Geological Society of America Bulletin |url=https://core.ac.uk/download/pdf/159286331.pdf |volume=75 |issue=3 |pages=191–208 |doi=10.1130/0016-7606(1964)75[191:PGITWS]2.0.CO;2 }}</ref> In the [[Southern Hemisphere]], there is some evidence for former permafrost from this period in central [[Otago]] and [[Argentina|Argentine]] [[Patagonia]], but was probably discontinuous, and is related to the tundra. Alpine permafrost also occurred in the [[Drakensberg]] during glacial maxima above about {{convert|3000|m|ft|-1}}.<ref>{{cite journal |last1=Grab |first1=Stefan |date=17 December 2001 |title=Characteristics and palaeoenvironmental significance of relict sorted patterned ground, Drakensberg plateau, southern Africa |journal=Quaternary Science Reviews |volume=21 |issue=14–15 |pages=1729–1744 |doi=10.1016/S0277-3791(01)00149-4 }}</ref><ref>{{cite journal |last1=Trombotto |first1=Dario |date=17 December 2001 |title=Inventory of fossil cryogenic forms and structures in Patagonia and the mountains of Argentina beyond the Andes |journal=South African Journal of Science |url=https://core.ac.uk/download/pdf/159286331.pdf |volume=98 |pages=171–180 }}</ref>

== Manifestations ==
{| class="wikitable floatright" style="margin: 1em auto; text-align:center;"
|+ Time required for permafrost to reach depth at [[Prudhoe Bay, Alaska]]<ref name="Lunardini1995" />{{rp|35}}
! Time (yr) !! Permafrost depth
|-
| 1 || {{Convert|4.44|m|ft|abbr=on}}
|-
| 350 || {{Convert|79.9|m|ft|abbr=on}}
|-
| 3,500 || {{Convert|219.3|m|ft|abbr=on}}
|-
| 35,000 || {{Convert|461.4|m|ft|abbr=on}}
|-
| 100,000 || {{Convert|567.8|m|ft|abbr=on}}
|-
| 225,000 || {{Convert|626.5|m|ft|abbr=on}}
|-
| 775,000 || {{Convert|687.7|m|ft|abbr=on}}
|}

=== Base depth ===
Permafrost extends to a base depth where geothermal heat from the Earth and the mean annual temperature at the surface achieve an equilibrium temperature of {{convert|0|°C|°F|abbr=on}}.<ref name="Ostercamp-Burn2003">{{Cite book |last1=Osterkamp |first1=T.E. |last2=Burn |first2=C.R. |contribution=Permafrost |title=Encyclopedia of Atmospheric Sciences |year=2003 |editor-last=North |editor-first=Gerald R. |editor-last2=Pyle |editor-first2=John A. |editor-last3=Zhang |editor-first3=Fuqing |volume=4 |pages=1717–1729 |url=http://curry.eas.gatech.edu/Courses/6140/ency/Chapter11/Ency_Atmos/Permafrost.pdf |publisher=Elsevier |isbn=978-0-12-382226-0 |access-date=8 March 2016 |archive-url=https://web.archive.org/web/20161130124841/http://curry.eas.gatech.edu/Courses/6140/ency/Chapter11/Ency_Atmos/Permafrost.pdf |archive-date=30 November 2016 |url-status=live }}</ref> This base depth of permafrost can vary wildly – it is less than a meter (3&nbsp;ft) in the areas where it is shallowest,<ref name="IPADefinition" /> yet reaches {{convert|1493|m|ft|abbr=on}} in the northern [[Lena River|Lena]] and [[Yana River]] basins in [[Siberia]].<ref name="Desonie2008">{{cite book| last=Desonie |first=Dana |title=Polar Regions: Human Impacts |publisher=Chelsea Press |year=2008 |location= New York |isbn=978-0-8160-6218-8 |url=https://archive.org/details/polarregionshuma0000deso }}</ref> Calculations indicate that the formation time of permafrost greatly slows past the first several metres. For instance, over half a million years was required to form the deep permafrost underlying [[Prudhoe Bay, Alaska]], a time period extending over several glacial and interglacial cycles of the [[Pleistocene]].<ref name="Lunardini1995">{{cite report |last=Lunardini |first=Virgil J. |title=Permafrost Formation Time |date=April 1995 |work=CRREL Report 95-8 |publisher=US Army Corps of Engineers Cold Regions Research and Engineering Laboratory |id={{DTIC|ADA295515}} |location=Hanover NH }}</ref>{{rp|18}}

Base depth is affected by the underlying geology, and particularly by [[thermal conductivity]], which is lower for permafrost in soil than in [[bedrock]].<ref name="Ostercamp-Burn2003" /> Lower conductivity leaves permafrost less affected by the [[geothermal gradient]], which is the rate of increasing temperature with respect to increasing depth in the Earth's interior. It occurs as the Earth's internal [[thermal energy]] is generated by [[radioactive decay]] of unstable [[isotope]]s and flows to the surface by conduction at a rate of ~47 [[terawatts]] (TW).<ref>{{cite journal |last1=Davies |first1=J.H. |last2=Davies |first2=D.R. |date=22 February 2010 |title=Earth's surface heat flux |volume=1 |issue=1 |pages=5–24 |journal=Solid Earth |doi=10.5194/se-1-5-2010 |bibcode=2010SolE....1....5D |doi-access=free }}</ref> Away from tectonic plate boundaries, this is equivalent to an average heat flow of 25–30&nbsp;°C/km (124–139&nbsp;°F/mi) near the surface.<ref name="IPCC2008">{{cite report |first1=Ingvar B. |last1=Fridleifsson |first2=Ruggero |last2=Bertani |first3=Ernst |last3=Huenges |first4=John W. |last4=Lund |first5=Arni |last5=Ragnarsson |first6=Ladislaus |last6=Rybach |date=11 February 2008 |title=The possible role and contribution of geothermal energy to the mitigation of climate change |editor=O. Hohmeyer and T. Trittin |location=IPCC Scoping Meeting on Renewable Energy Sources, Luebeck, Germany |pages=59–80 |url=https://www.researchgate.net/publication/284685252 |access-date=27 September 2023 |archive-url=https://web.archive.org/web/20130312182133/http://ipcc.ch/pdf/supporting-material/proc-renewables-lubeck.pdf | archive-date=12 March 2013 }}</ref>

=== Massive ground ice ===
[[File:Coulombe 2019 ground ice diagram.png|thumb|Labelled example of a massive buried ice deposit in [[Bylot Island]], Canada.<ref name="Coulombe2019" />]]

When the ice content of a permafrost exceeds 250 percent (ice to dry soil by mass) it is classified as massive ice. Massive ice bodies can range in composition, in every conceivable gradation from icy [[mud]] to pure ice. Massive icy beds have a minimum thickness of at least 2&nbsp;m and a short [[diameter]] of at least 10&nbsp;m.<ref name="Mackay1973">{{Cite conference |last=Mackay |first=J. Ross |title=Problems in the origins of massive icy beds, Western Arctic, Canada |conference=Permafrost: North American Contribution – Second International Conference |volume=2 |pages=223–228 |year=1973 |isbn=978-0-309-02115-9 |url=https://books.google.com/books?id=SjErAAAAYAAJ&pg=PA191 }}</ref> First recorded North American observations of this phenomenon were by European scientists at [[Canning River (Alaska)]] in 1919.<ref name="French2007">{{cite book |last=French |first=H.M. |title=The Periglacial Environment |publisher=Wiley |edition=3 |date=26 January 2007 |location=Chichester |chapter=5 |pages=83–115 |isbn=978-1-118-68493-1 |doi=10.1002/9781118684931.ch5 }}</ref> Russian literature provides an earlier date of 1735 and 1739 during the Great North Expedition by P. Lassinius and [[Khariton Laptev]], respectively. Russian investigators including I.A. Lopatin, B. Khegbomov, S. Taber and G. Beskow had also formulated the original theories for ice inclusion in freezing soils.<ref name="Shumskiy-Vtyurin1963">{{Cite conference |last1=Shumskiy |first1=P.A. |last2=Vtyurin |first2=B.I. |title=Underground ice |conference=Permafrost International Conference |issue=1287 |pages=108–113 |year=1963 |url=https://books.google.com/books?id=3jErAAAAYAAJ&q=utilidors+in+permafrost&pg=PA441 }}</ref>

While there are four categories of ice in permafrost – pore ice, ice wedges (also known as vein ice), buried surface ice and intrasedimental (sometimes also called constitutional<ref name="Shumskiy-Vtyurin1963" />) ice – only the last two tend to be large enough to qualify as massive ground ice.<ref name="Mackay1992">{{Cite journal |last1=Mackay |first1=J.R. |last2=Dallimore |first2=S.R. |title=Massive ice of Tuktoyaktuk area, Western Arctic coast, Canada |journal=Canadian Journal of Earth Sciences |volume=29 |issue=6 |pages=1234–1242 |doi=10.1139/e92-099 |year=1992 |bibcode=1992CaJES..29.1235M }}</ref><ref name="Lacelle2022">{{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 }}</ref> These two types usually occur separately, but may be found together, like on the coast of [[Tuktoyaktuk]] in western [[Arctic Canada]], where the remains of [[Laurentide Ice Sheet]] are located.<ref>{{cite journal |last1=Murton |first1=J. B. |last2=Whiteman |first2=C. A. |last3=Waller |first3=R. I. |last4=Pollard |first4=W. H. |last5=Clark |first5=I. D. |last6=Dallimore |first6=S. R. |date=12 August 2004 |title=Basal ice facies and supraglacial melt-out till of the Laurentide Ice Sheet, Tuktoyaktuk Coastlands, western Arctic Canada |journal=Quaternary Science Reviews |volume=24 |issue=5–6 |pages=681–708 |doi=10.1016/S0277-3791(01)00149-4 }}</ref>

Buried surface ice may derive from snow, frozen lake or [[sea ice]], [[aufeis]] (stranded river ice) and even buried glacial ice from the former [[Pleistocene]] ice sheets. The latter hold enormous value for paleoglaciological research, yet even as of 2022, the total extent and volume of such buried ancient ice is unknown.<ref name="Coulombe2022">{{cite journal |last1=Coulombe |first1=Stephanie |last2=Fortier |first2=Daniel |last3=Bouchard |first3=Frédéric |last4=Paquette |first4=Michel |last5=Charbonneau |first5=Simon |last6=Lacelle |first6=Denis |last7=Laurion |first7=Isabelle |last8=Pienitz |first8=Reinhard |title=Contrasted geomorphological and limnological properties of thermokarst lakes formed in buried glacier ice and ice-wedge polygon terrain |journal=The Cryosphere |date=19 July 2022 |volume=16 |issue=7 |pages=2837–2857 |doi=10.5194/tc-16-2837-2022 |bibcode=2022TCry...16.2837C |doi-access=free }}</ref> Notable sites with known ancient ice deposits include [[Yenisei River]] valley in [[Siberia]], Russia as well as [[Banks Island|Banks]] and [[Bylot Island]] in Canada's [[Nunavut]] and [[Northwest Territories]].<ref>{{Cite journal |last1=Astakhov |first1=Valery I. |last2=Isayeva |first2=Lia L. |title=The 'Ice Hill': An example of 'retarded deglaciation' in siberia |journal=Quaternary Science Reviews |year=1988 |volume=7 |issue=1 |pages=29–40 |doi=10.1016/0277-3791(88)90091-1 |bibcode=1988QSRv....7...29A }}</ref><ref>{{Cite journal |last1=French |first1=H. M. |last2=Harry |first2=D. G. |title=Observations on buried glacier ice and massive segregated ice, western arctic coast, Canada |journal=Permafrost and Periglacial Processes |year=1990 |volume=1 |issue=1 |pages=31–43 |doi=10.1002/ppp.3430010105 |bibcode=1990PPPr....1...31F }}</ref><ref name="Coulombe2019">{{cite journal |last1=Coulombe |first1=Stephanie |last2=Fortier |first2=Daniel |last3=Lacelle |first3=Denis |last4=Kanevskiy |first4=Mikhail |last5=Shur |first5=Yuri |title=Origin, burial and preservation of late Pleistocene-age glacier ice in Arctic permafrost (Bylot Island, NU, Canada) |journal=The Cryosphere |date=11 January 2019 |volume=13 |issue=1 |pages=97–111 |doi=10.5194/tc-13-97-2019 |bibcode=2019TCry...13...97C |doi-access=free }}</ref> Some of the buried ice sheet remnants are known to host [[Thermokarst#Thermokarst lakes|thermokarst lake]]s.<ref name="Coulombe2022" />

Intrasedimental or constitutional ice has been widely observed and studied across Canada. It forms when subterranean waters freeze in place, and is subdivided into intrusive, injection and segregational ice. The latter is the dominant type, formed after crystallizational differentiation in wet [[sediment]]s, which occurs when water migrates to the freezing front under the influence of [[van der Waals force]]s.<ref name="French2007" /><ref name="Mackay1973" /><ref name="Mackay1992" /> This is a slow process, which primarily occurs in [[silt]]s with [[salinity]] less than 20% of [[seawater]]: silt sediments with higher salinity and [[clay]] sediments instead have water movement prior to ice formation dominated by [[rheological]] processes. Consequently, it takes between 1 and 1000 years to form intrasedimental ice in the top 2.5 meters of clay sediments, yet it takes between 10 and 10,000 years for [[peat]] sediments and between 1,000 and 1,000,000 years for silt sediments.<ref name="Lacelle2022" />

[[File:Massive ice - retrogressive thaw slump - Herschel Island.png|thumb|center|900px|Cliff wall of a retrogressive thaw slump located on the southern coast of [[Herschel Island]] within an approximately {{convert|22|m|ft|adj=on}} by {{convert|1300|m|ft|adj=on}} headwall.]]

=== Landforms ===
{{See also|Patterned ground}}
Permafrost processes such as [[thermal contraction]] generating cracks which eventually become [[ice wedge]]s and [[solifluction]] – gradual movement of soil down the slope as it repeatedly freezes and thaws – often lead to the formation of ground polygons, rings, steps and other forms of [[patterned ground]] found in arctic, periglacial and alpine areas.<ref>{{cite journal |last1=Black |first1=Robert F. |year=1976 |title=Periglacial Features Indicative of Permafrost: Ice and Soil Wedges |journal=Quaternary Research |volume=6 |issue=1 |pages=3–26 |doi=10.1016/0033-5894(76)90037-5 |bibcode=1976QuRes...6....3B |s2cid=128393192 }}</ref><ref>{{cite journal |last1=Kessler |first1=M. A. |last2=Werner |first2=B. T. |title=Self-organization of sorted patterned ground |journal=Science |volume=299 |issue=5605 |pages=380–383 |date=17 January 2003 |pmid=12532013 |doi=10.1126/science.1077309 |bibcode=2003Sci...299..380K |s2cid=27238820 }}</ref> In ice-rich permafrost areas, melting of ground ice initiates [[thermokarst]] landforms such as [[thermokarst lake]]s, thaw slumps, thermal-erosion gullies, and active layer detachments.<ref>{{cite journal |last1=Li |first1=Dongfeng |last2=Overeem |first2=Irina |last3=Kettner |first3=Albert J. |last4=Zhou |first4=Yinjun |last5=Lu |first5=Xixi |title=Air Temperature Regulates Erodible Landscape, Water, and Sediment Fluxes in the Permafrost-Dominated Catchment on the Tibetan Plateau |journal=Water Resources Research |date=February 2021 |volume=57 |issue=2 |pages=e2020WR028193 |doi=10.1029/2020WR028193 |bibcode=2021WRR....5728193L |s2cid=234044271 }}</ref><ref>{{cite journal |last1=Zhang |first1=Ting |last2=Li |first2=Dongfeng |last3=Kettner |first3=Albert J. |last4=Zhou |first4=Yinjun |last5=Lu |first5=Xixi |title=Constraining Dynamic Sediment-Discharge Relationships in Cold Environments: The Sediment-Availability-Transport (SAT) Model |journal=Water Resources Research |date=October 2021 |volume=57 |issue=10 |pages=e2021WR030690 |doi=10.1029/2021WR030690 |bibcode=2021WRR....5730690Z |s2cid=242360211 }}</ref> Notably, unusually deep permafrost in Arctic [[moorland]]s and [[bog]]s often attracts meltwater in warmer seasons, which pools and freezes to form [[ice lense]]s, and the surrounding ground begins to jut outward at a slope. This can eventually result in the formation of large-scale land forms around this core of permafrost, such as [[palsa]]s – long ({{cvt|15|-|150|m|abbr=on|0}}), wide ({{cvt|10|-|30|m|abbr=on|0}}) yet shallow (<{{cvt|1|-|6|m|abbr=on|0}} tall) [[peat]] [[mound]]s – and the even larger [[pingo]]s, which can be {{cvt|3|-|70|m|abbr=on|0}} high and {{cvt|30|-|1000|m|abbr=on}} in [[diameter]].<ref>{{cite web|last=Pidwirny|first=M|title=Periglacial Processes and Landforms|url=http://www.physicalgeography.net/fundamentals/10ag.html|work=Fundamentals of Physical Geography|year=2006}}</ref><ref>{{Cite journal|last1=Kujala|first1=Kauko|last2=Seppälä |first2=Matti|last3=Holappa|first3=Teuvo|date=2008|title=Physical properties of peat and palsa formation |url=http://www.sciencedirect.com/science/article/pii/S0165232X07001644 |journal=Cold Regions Science and Technology|language=en|volume=52|issue=3|pages=408–414|doi=10.1016/j.coldregions.2007.08.002|bibcode=2008CRST...52..408K |issn=0165-232X}}</ref>

<gallery mode="packed" heights="150px">
File:Palsaaerialview.jpg|A group of [[palsa]]s, as seen from above, formed by the growth of ice lenses.
File:Pingos near Tuk.jpg|[[Pingo]]s near [[Tuktoyaktuk]], [[Northwest Territories]], Canada
File:Permafrost - polygon.jpg|[[Patterned ground#Polygons|Ground polygons]]
File:Permafrost stone-rings hg.jpg|[[Patterned ground#Circles|Stone rings]] on [[Spitsbergen]]
File:Polygons in Padjelanta.jpg|[[Helicopter]] view of ground polygons and ice lenses at [[Padjelanta National Park]], Sweden
File:Ice-wedge hg.jpg|[[Ice wedge]]s seen from top
File:Permafrost soil-flow hg.jpg|[[Solifluction]] on [[Svalbard]]
File:Permafrost pattern.jpg|Contraction crack ([[ice wedge]]) polygons on Arctic sediment.
</gallery>

=== Ecology ===
[[File:Peat Plateau Complex.jpg|thumb|A peat plateau complex south of [[Fort Simpson]], [[Northwest Territories]].]]
Only plants with shallow [[root]]s can survive in the presence of permafrost. [[Black spruce]] tolerates limited rooting zones, and dominates [[flora]] where permafrost is extensive. Likewise, animal [[species]] which live in dens and [[burrow]]s have their habitat constrained by the permafrost, and these constraints also have a secondary impact on interactions between species within the [[ecosystem]].<ref>{{cite web |url=https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_1/picea/mariana.htm |title=Black Spruce |publisher=[[USDA]] |access-date=27 September 2023 }}</ref>
[[File:Storflaket.JPG|thumb|left|Cracks forming at the edges of the [[Storflaket]] permafrost bog in Sweden.]]
While permafrost soil is frozen, it is not completely inhospitable to [[microorganism]]s, though their numbers can vary widely, typically from 1 to 1000&nbsp;million per gram of soil.<ref>{{cite journal | last1 = Hansen |display-authors=etal | year = 2007 | title = Viability, diversity and composition of the bacterial community in a high Arctic permafrost soil from Spitsbergen, Northern Norway | journal = Environmental Microbiology | volume = 9 | issue = 11| pages = 2870–2884 | doi=10.1111/j.1462-2920.2007.01403.x| pmid = 17922769|bibcode=2007EnvMi...9.2870H }}</ref><ref>{{cite journal | last1 = Yergeau |display-authors=etal | year = 2010 | title = The functional potential of high Arctic permafrost revealed by metagenomic sequencing, qPCR and microarray analyses | journal = The ISME Journal | volume = 4 | issue = 9| pages = 1206–1214 | doi=10.1038/ismej.2010.41| pmid = 20393573| doi-access = free |bibcode=2010ISMEJ...4.1206Y }}</ref>
The [[permafrost carbon cycle]] (Arctic Carbon Cycle) deals with the transfer of carbon from permafrost soils to terrestrial vegetation and microbes, to the atmosphere, back to vegetation, and finally back to permafrost soils through burial and sedimentation due to cryogenic processes. Some of this carbon is transferred to the ocean and other portions of the globe through the global carbon cycle. The cycle includes the exchange of [[carbon dioxide]] and [[methane]] between terrestrial components and the atmosphere, as well as the transfer of carbon between land and water as methane, [[dissolved organic carbon]], [[dissolved inorganic carbon]], [[particulate inorganic carbon]] and [[particulate organic carbon]].<ref name=mcguire>{{Cite journal |doi=10.1890/08-2025.1 |author1=McGuire, A.D. |author2=Anderson, L.G. |author3=Christensen, T.R. |author4=Dallimore, S. |author5=Guo, L. |author6=Hayes, D.J. |author7=Heimann, M. |author8=Lorenson, T.D. |author9=Macdonald, R.W. |author10=Roulet, N. |title=Sensitivity of the carbon cycle in the Arctic to climate change |journal=Ecological Monographs |volume=79 |issue=4 |pages=523–555 |year=2009 |bibcode=2009EcoM...79..523M |hdl=11858/00-001M-0000-000E-D87B-C |s2cid=1779296 |hdl-access=free }}</ref>

Most of the bacteria and fungi found in permafrost cannot be cultured in the laboratory, but the identity of the microorganisms can be revealed by [[DNA]]-based techniques. For instance, analysis of 16S [[rRNA]] genes from late [[Pleistocene]] permafrost samples in eastern [[Siberia]]'s [[Kolyma Lowland]] revealed eight [[phylotype]]s, which belonged to the phyla [[Actinomycetota]] and [[Pseudomonadota]].<ref>{{Cite journal|last1=Kudryashova|first1=E. B.|last2=Chernousova|first2=E. Yu.|last3=Suzina|first3=N. E.|last4=Ariskina|first4=E. V.|last5=Gilichinsky|first5=D. A.|date=2013-05-01|title=Microbial diversity of Late Pleistocene Siberian permafrost samples|journal=Microbiology |volume=82|issue=3|pages=341–351 |doi=10.1134/S0026261713020082|s2cid=2645648 }}</ref> "Muot-da-Barba-Peider", an alpine permafrost site in eastern Switzerland, was found to host a diverse microbial community in 2016. Prominent bacteria groups included phylum [[Acidobacteriota]], [[Actinomycetota]], AD3, [[Bacteroidota]], [[Chloroflexota]], [[Gemmatimonadota]], OD1, [[Nitrospirota]], [[Planctomycetota]], [[Pseudomonadota]], and [[Verrucomicrobiota]], in addition to [[eukaryotic]] fungi like [[Ascomycota]], [[Basidiomycota]], and [[Zygomycota]]. In the presently living species, scientists observed a variety of adaptations for sub-zero conditions, including reduced and anaerobic metabolic processes.<ref>{{Cite journal|last1=Frey|first1=Beat|last2=Rime|first2=Thomas|last3=Phillips|first3=Marcia|last4=Stierli|first4=Beat|last5=Hajdas|first5=Irka|last6=Widmer|first6=Franco|last7=Hartmann|first7=Martin|date=March 2016|editor-last=Margesin|editor-first=Rosa|title=Microbial diversity in European alpine permafrost and active layers|journal=FEMS Microbiology Ecology |volume=92|issue=3|pages=fiw018|doi=10.1093/femsec/fiw018|pmid=26832204 |doi-access=free}}</ref>

=== Construction on permafrost ===

There are only two large cities in the world built in areas of continuous permafrost (where the frozen soil forms an unbroken, below-zero sheet) and both are in Russia – [[Norilsk]] in [[Krasnoyarsk Krai]] and [[Yakutsk]] in the [[Sakha Republic]].<ref name="NY11022">{{cite magazine|author1=Joshua Yaffa|date=January 20, 2022|title=The Great Siberian Thaw|magazine=The New Yorker|url=https://www.newyorker.com/magazine/2022/01/17/the-great-siberian-thaw|access-date=January 20, 2022}}</ref> Building on permafrost is difficult because the heat of the building (or [[pipeline transport|pipeline]]) can spread to the soil, thawing it. As ice content turns to water, the ground's ability to provide structural support is weakened, until the building is destabilized. For instance, during the construction of the [[Trans-Siberian Railway]], a [[steam engine]] factory complex built in 1901 began to crumble within a month of operations for these reasons.<ref name="Chu2020" />{{rp|47}} Additionally, there is no [[groundwater]] available in an area underlain with permafrost. Any substantial settlement or installation needs to make some alternative arrangement to obtain water.<ref name="NY11022" /><ref name="Chu2020" />{{rp|25}}

A common solution is placing [[foundation (architecture)|foundations]] on wood [[Deep foundation|piles]], a technique pioneered by Soviet engineer [[Mikhail Kim]] in Norilsk.<ref>{{Cite magazine|last=Yaffa|first=Joshua|date=2022-01-07|title=The Great Siberian Thaw|url=https://www.newyorker.com/magazine/2022/01/17/the-great-siberian-thaw|access-date=2022-01-12|magazine=The New Yorker }}</ref> However, warming-induced change of [[friction]] on the piles can still cause movement through [[Creep (deformation)|creep]], even as the soil remains frozen.<ref>{{Cite book|last=Fang|first=Hsai-Yang|url=https://books.google.com/books?id=X8hEt3l1SPQC&q=foundations+on+permafrost&pg=PA735|title=Foundation Engineering Handbook|date=1990-12-31|publisher=Springer Science & Business Media|isbn=978-0-412-98891-2|page=735 }}</ref> The [[Melnikov Permafrost Institute]] in Yakutsk found that pile foundations should extend down to {{convert|15|m}} to avoid the risk of buildings sinking. At this depth the temperature does not change with the seasons, remaining at about {{convert|-5|C}}.<ref>{{Cite book|last1=Sanger|first1=Frederick J.|url=https://books.google.com/books?id=YDArAAAAYAAJ&q=yakutsk+pile+foundations+on+permafrost&pg=PA786|title=Permafrost: Second International Conference, July 13–28, 1973 : USSR Contribution|last2=Hyde|first2=Peter J.|date=1978-01-01|publisher=National Academies|isbn=978-0-309-02746-5|page=786 }}</ref>

Two other approaches are building on an extensive [[gravel]] pad (usually {{cvt|1-2|m}} thick); or using [[anhydrous ammonia]] [[heat pipe]]s.<ref name="ASCE">{{cite book |last=Clarke |first=Edwin S. |title=Permafrost Foundations—State of the Practice |series=Monograph Series |publisher=American Society of Civil Engineers |year=2007 |url=https://books.google.com/books?id=O-voTug5apsC&pg=PA34 |isbn=978-0-7844-0947-3}}</ref> The [[Trans-Alaska Pipeline System]] uses [[Heat pipe#Permafrost cooling|heat pipes built into vertical supports]] to prevent the pipeline from sinking and the [[Qingzang railway]] in Tibet employs a variety of methods to keep the ground cool, both in areas with [[Frost heaving#Frost-susceptible soils|frost-susceptible soil]]. Permafrost may necessitate special enclosures for buried utilities, called "[[Utility tunnel#In Arctic towns|utilidors]]".<ref>{{Cite book|last=Woods|first=Kenneth B.|url=https://books.google.com/books?id=3jErAAAAYAAJ&q=utilidors+in+permafrost&pg=PA441|title=Permafrost International Conference: Proceedings|date=1966|publisher=National Academies|pages=418–57 }}</ref>

{{Clear}}
<gallery mode="packed" heights="150px">
File:PICT4417Sykhus.JPG|A building on elevated piles in permafrost zone.
File:Trans-Alaska Pipeline (1).jpg|[[Heat pipe#Permafrost cooling|Heat pipes in vertical supports]] maintain a frozen bulb around portions of the [[Trans-Alaska Pipeline]] that are at risk of thawing.<ref>{{Cite web |url=http://apps.dtic.mil/dtic/tr/fulltext/u2/a073597.pdf |title=C. E Heuer, "The Application of Heat Pipes on the Trans-Alaska Pipeline" Special Report 79-26, United States Army Corps of Engineers, Sept. 1979. |access-date=2013-10-22 |archive-date=2013-10-22 |archive-url=https://web.archive.org/web/20131022022419/http://www.dtic.mil/dtic/tr/fulltext/u2/a073597.pdf |url-status=live }}</ref>
File:Yakoutsk Construction d'immeuble.jpg|Pile foundations in [[Yakutsk]], a city underlain with continuous permafrost.
File:Raised pipes in permafrost.jpg|[[District heating]] pipes run above ground in Yakutsk.
</gallery>

== Impacts of climate change ==
{{See also|Effects of climate change}}
[[File:Beaufort Permafrost2.JPG|thumb|left|Recently thawed Arctic permafrost and coastal erosion on the Beaufort Sea, Arctic Ocean, near [[Point Lonely Short Range Radar Site|Point Lonely, Alaska]] in 2013.]]

Globally, permafrost warmed by about {{cvt|0.3|C-change}} between 2007 and 2016, with stronger warming observed in the continuous permafrost zone relative to the discontinuous zone. Observed warming was up to {{convert|3|C-change|F-change}} in parts of [[Northern Alaska]] (early 1980s to mid-2000s) and up to {{convert|2|C-change|F-change}} in parts of the Russian European North (1970–2020). This warming inevitably causes permafrost to thaw: [[active layer]] thickness has increased in the European and [[Russian Arctic]] across the 21st century and at high elevation areas in Europe and Asia since the 1990s.<ref name="AR6_WG1_Chapter922">Fox-Kemper, B., H.T. Hewitt, C. Xiao, G. Aðalgeirsdóttir, S.S. Drijfhout, T.L. Edwards, N.R. Golledge, M. Hemer, R.E. Kopp, G.&nbsp; Krinner, A. Mix, D. Notz, S. Nowicki, I.S. Nurhati, L. Ruiz, J.-B. Sallée, A.B.A. Slangen, and Y. Yu, 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter09.pdf Chapter 9: Ocean, Cryosphere and Sea Level Change]. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L.&nbsp; Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1211–1362, doi:10.1017/9781009157896.011.</ref>{{rp|1237}} Between 2000 and 2018, the average active layer thickness had increased from ~{{convert|127|cm|ft}} to ~{{convert|145|cm|ft}}, at an average annual rate of ~{{convert|0.65|cm|in}}.<ref name="Li2022" /> In [[Yukon]], the zone of continuous permafrost might have moved {{convert|100|km}} poleward since 1899, but accurate records only go back 30 years. The extent of subsea permafrost is decreasing as well; as of 2019, ~97% of permafrost under Arctic ice shelves is becoming warmer and thinner.<ref>{{Cite journal |last1=Overduin |first1=P. P. |last2=Schneider von Deimling |first2=T. |last3=Miesner |first3=F. |last4=Grigoriev |first4=M. N. |last5=Ruppel |first5=C. |last6=Vasiliev |first6=A. |last7=Lantuit |first7=H. |last8=Juhls |first8=B. |last9=Westermann |first9=S. |date=17 April 2019 |title=Submarine Permafrost Map in the Arctic Modeled Using 1-D Transient Heat Flux (SuPerMAP) |journal=Journal of Geophysical Research: Oceans |volume=124 |issue=6 |pages=3490–3507 |doi=10.1029/2018JC014675 |bibcode=2019JGRC..124.3490O |hdl=1912/24566 |s2cid=146331663 |url=https://epic.awi.de/id/eprint/49740/1/Overduin_etal2019_ePIC.pdf }}</ref><ref name="AR6_WG1_Chapter92" />{{rp|1281}} Based on high agreement across model projections, fundamental process understanding, and paleoclimate evidence, it is virtually certain that permafrost extent and volume will continue to shrink as the global climate warms, with the extent of the losses determined by the magnitude of warming.<ref name="AR6_WG1_Chapter922" />{{rp|1283}}

Permafrost thaw is associated with a wide range of issues, and [[International Permafrost Association]] (IPA) exists to help address them. It convenes International Permafrost Conferences and maintains [[Global Terrestrial Network for Permafrost]], which undertakes special projects such as preparing databases, maps, bibliographies, and glossaries, and coordinates international field programmes and networks.<ref>{{cite web|author= |url=https://www.permafrost.org/frozen-ground-newsletter/ |title=Frozen Ground, the News Bulletin of the IPA |language= |website=International Permafrost Association |date= 2014-02-10|accessdate=2016-04-28}}</ref>

=== Climate change feedback ===
{{Main|Permafrost carbon cycle}}
[[File:Hugelius 2020 peatland projections.jpg|thumb|Permafrost peatlands (a smaller, carbon-rich subset of permafrost areas) under varying extent of global warming, and the resultant emissions as a fraction of anthropogenic emissions needed to cause that extent of warming.<ref name="Hugelius2020">{{Cite journal |last1=Hugelius |first1=Gustaf |last2=Loisel |first2=Julie |last3=Chadburn |first3=Sarah |display-authors=etal |date=10 August 2020 |title=Large stocks of peatland carbon and nitrogen are vulnerable to permafrost thaw |journal=Proceedings of the National Academy of Sciences |volume=117 |issue=34 |pages=20438–20446 |bibcode=2020PNAS..11720438H |doi=10.1073/pnas.1916387117 |pmc=7456150 |pmid=32778585 |doi-access=free}}</ref>
]]

As recent warming deepens the active layer subject to permafrost thaw, this exposes formerly stored [[carbon]] to biogenic processes which facilitate its entrance into the atmosphere as [[carbon dioxide]] and [[methane]].<ref name="Schuur2022" /> Because carbon emissions from permafrost thaw contribute to the same warming which facilitates the thaw, it is a well-known example of a [[Climate change feedback#Positive feedbacks|positive climate change feedback]],<ref name="Natali2020">{{Cite journal |last1=Natali |first1=Susan M. |last2=Holdren |first2=John P. |last3=Rogers |first3=Brendan M. |last4=Treharne |first4=Rachael |last5=Duffy |first5=Philip B. |last6=Pomerance |first6=Rafe |last7=MacDonald |first7=Erin |date=10 December 2020 |title=Permafrost carbon feedbacks threaten global climate goals |journal=Biological Sciences |volume=118 |issue=21 |doi=10.1073/pnas.2100163118 |pmc=8166174 |pmid=34001617 |doi-access=free}}</ref> and because widespread permafrost thaw is effectively irreversible, it is also considered one of [[tipping points in the climate system]].<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 |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 |pages=eabn7950 |doi=10.1126/science.abn7950 |issn=0036-8075 |pmid=36074831 |s2cid=252161375 |hdl-access=free |hdl=10871/131584}}</ref>

In the northern circumpolar region, permafrost contains organic matter equivalent to 1400–1650&nbsp;billion tons of pure carbon, which was built up over thousands of years. This amount equals almost half of all organic material in all [[soil]]s,<ref name="Tarnocai2009">{{cite journal |last1=Tarnocai, C. |author2=Canadell, J.G. |author3=Schuur, E.A.G. |author4=Kuhry, P. |author5=Mazhitova, G. |author6=Zimov, S. |date=June 2009 |title=Soil organic carbon pools in the northern circumpolar permafrost region |journal=Global Biogeochemical Cycles |volume=23 |issue=2 |page=GB2023 |bibcode=2009GBioC..23.2023T |doi=10.1029/2008gb003327 |doi-access=free}}</ref><ref name="Schuur2022" /> and it is about twice the carbon content of the [[atmosphere]], or around four times larger than the human emissions of carbon between the start of the [[Industrial Revolution]] and 2011.<ref name="Schuur2011">{{cite journal |last1=Schuur |display-authors=etal |year=2011 |title=High risk of permafrost thaw |url=https://digital.library.unt.edu/ark:/67531/metadc836756/ |journal=Nature |volume=480 |issue=7375 |pages=32–33 |bibcode=2011Natur.480...32S |doi=10.1038/480032a |pmid=22129707 |s2cid=4412175 |doi-access=free}}</ref> Further, most of this carbon (~1,035&nbsp;billion tons) is stored in what is defined as the near-surface permafrost, no deeper than {{convert|3|m|ft}} below the surface.<ref name="Tarnocai2009" /><ref name="Schuur2022" /> However, only a fraction of this stored carbon is expected to enter the atmosphere.<ref name="Bockheim2007">{{Cite journal |author1=Bockheim, J.G. |author2=Hinkel, K.M. |name-list-style=amp |year=2007 |title=The importance of "Deep" organic carbon in permafrost-affected soils of Arctic Alaska |url=http://soil.scijournals.org/cgi/content/abstract/71/6/1889 |url-status=dead |journal=Soil Science Society of America Journal |volume=71 |issue=6 |pages=1889–92 |bibcode=2007SSASJ..71.1889B |doi=10.2136/sssaj2007.0070N |archive-url=https://web.archive.org/web/20090717063627/http://soil.scijournals.org/cgi/content/abstract/71/6/1889 |archive-date=17 July 2009 |access-date=5 June 2010}}</ref> In general, the volume of permafrost in the upper 3&nbsp;m of ground is expected to decrease by about 25% per {{convert|1|C-change|F-change}} of global warming,<ref name="AR6_WG1_Chapter922" />{{rp|1283}} yet even under the [[Representative Concentration Pathway#RCP8.5|RCP8.5]] scenario associated with over {{convert|4|C-change|F-change}} of global warming by the end of the 21st century,<ref name="ar5 21st century projections">IPCC: Table SPM-2, in: [http://www.climatechange2013.org/images/report/WG1AR5_SPM_FINAL.pdf Summary for Policymakers] (archived [https://web.archive.org/web/20140716042158/http://www.climatechange2013.org/images/report/WG1AR5_SPM_FINAL.pdf 16 July 2014]), in: {{harvnb|IPCC AR5 WG1|2013|p=21}}</ref> about 5% to 15% of permafrost carbon is expected to be lost "over decades and centuries".<ref name="Schuur2022" />

The exact amount of carbon that will be released due to warming in a given permafrost area depends on depth of thaw, carbon content within the thawed soil, physical changes to the environment, and microbial and vegetation activity in the soil.<ref name="Nowinski2010">{{Cite journal |vauthors=Nowinski NS, Taneva L, [[Susan Trumbore|Trumbore SE]], Welker JM |date=January 2010 |title=Decomposition of old organic matter as a result of deeper active layers in a snow depth manipulation experiment |journal=Oecologia |volume=163 |issue=3 |pages=785–92 |bibcode=2010Oecol.163..785N |doi=10.1007/s00442-009-1556-x |pmc=2886135 |pmid=20084398}}</ref> Notably, estimates of carbon release alone do not fully represent the impact of permafrost thaw on climate change. This is because carbon can be released through either [[aerobic respiration|aerobic]] or [[anaerobic respiration]], which results in carbon dioxide (CO2) or methane (CH4) emissions, respectively. While methane lasts less than 12 years in the atmosphere, its [[global warming potential]] is around 80 times larger than that of CO2 over a 20-year period and about 28 times larger over a 100-year period.<ref>{{Cite book |last1=Forster |first1=Piers |title={{Harvnb|IPCC AR6 WG1|2021}} |last2=Storelvmo |first2=Trude |year=2021 |chapter=Chapter 7: The Earth's Energy Budget, Climate Feedbacks, and Climate Sensitivity |ref={{harvid|IPCC AR6 WG1 Ch7|2021}} |chapter-url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter07.pdf}}</ref><ref>{{Cite journal |last1=Allen |first1=Robert J. |last2=Zhao |first2=Xueying |last3=Randles |first3=Cynthia A. |last4=Kramer |first4=Ryan J. |last5=Samset |first5=Bjørn H. |last6=Smith |first6=Christopher J. |date=16 March 2023 |title=Surface warming and wetting due to methane's long-wave radiative effects muted by short-wave absorption |journal=Nature Geoscience |volume=16 |issue=4 |pages=314–320 |bibcode=2023NatGe..16..314A |doi=10.1038/s41561-023-01144-z |s2cid=257595431}}</ref> While only a small fraction of permafrost carbon will enter the atmosphere as methane, those emissions will cause 40-70% of the total warming caused by permafrost thaw during the 21st century. Much of the uncertainty about the eventual extent of permafrost methane emissions is caused by the difficulty of accounting for the recently discovered abrupt thaw processes, which often increase the fraction of methane emitted over carbon dioxide in comparison to the usual gradual thaw processes.<ref>{{Cite journal |last1=Miner |first1=Kimberley R. |last2=Turetsky |first2=Merritt R. |last3=Malina |first3=Edward |last4=Bartsch |first4=Annett |last5=Tamminen |first5=Johanna |last6=McGuire |first6=A. David |last7=Fix |first7=Andreas |last8=Sweeney |first8=Colm |last9=Elder |first9=Clayton D. |last10=Miller |first10=Charles E. |date=11 January 2022 |title=Permafrost carbon emissions in a changing Arctic |url=https://www.nature.com/articles/s43017-021-00230-3 |journal=Nature Reviews Earth & Environment |volume=13 |issue=1 |pages=55–67 |bibcode=2022NRvEE...3...55M |doi=10.1038/s43017-021-00230-3 |s2cid=245917526}}</ref><ref name="Schuur2022" />
[[File:Permafrost thaw ponds in Hudson Bay Canada near Greenland.jpg|thumb|left|Permafrost thaw ponds on peatland in [[Hudson Bay]], Canada in 2008.<ref>{{cite journal |last1=Dyke |first1=Larry D. |last2=Sladen |first2=Wendy E. |date=3 December 2010 |title=Permafrost and Peatland Evolution in the Northern Hudson Bay Lowland, Manitoba |journal=Arctic |volume=63 |issue=4 |pages=429–441 |doi=10.14430/arctic3332 |doi-access=free}}</ref>]]
Another factor which complicates projections of permafrost carbon emissions is the ongoing "greening" of the Arctic. As climate change warms the air and the soil, the region becomes more hospitable to plants, including larger [[shrub]]s and trees which could not survive there before. Thus, the Arctic is losing more and more of its [[tundra]] biomes, yet it gains more plants, which proceed to absorb more carbon. Some of the emissions caused by permafrost thaw will be offset by this increased plant growth, but the exact proportion is uncertain. It is considered very unlikely that this greening could offset all of the emissions from permafrost thaw during the 21st century, and even less likely that it could continue to keep pace with those emissions after the 21st century.<ref name="Schuur2022" /> Further, climate change also increases the risk of [[wildfire]]s in the Arctic, which can substantially accelerate emissions of permafrost carbon.<ref name="Natali2020" /><ref>{{Cite journal |last1=Estop-Aragonés |first1=Cristian |last2=Czimczik |first2=Claudia I |last3=Heffernan |first3=Liam |last4=Gibson |first4=Carolyn |last5=Walker |first5=Jennifer C |last6=Xu |first6=Xiaomei |last7=Olefeldt |first7=David |date=13 August 2018 |title=Respiration of aged soil carbon during fall in permafrost peatlands enhanced by active layer deepening following wildfire but limited following thermokarst |journal=Environmental Research Letters |volume=13 |issue=8 |doi=10.1088/1748-9326/aad5f0|bibcode=2018ERL....13h5002E |s2cid=158857491 |doi-access=free }}</ref>

==== Impact on global temperatures ====
[[File:Schuur 2022 century-scale permafrost projections.jpeg|thumb|Nine probable scenarios of [[greenhouse gas emission]]s from permafrost thaw during the 21st century, which show a limited, moderate and intense {{CO2}} and {{CH4}} emission response to low, medium and high-emission [[Representative Concentration Pathway]]s. The vertical bar uses emissions of selected large countries as a comparison: the right-hand side of the scale shows their cumulative emissions since the start of the [[Industrial Revolution]], while the left-hand side shows each country's cumulative emissions for the rest of the 21st century if they remained unchanged from their 2019 levels.<ref name="Schuur2022" />]]

Altogether, it is expected that cumulative greenhouse gas emissions from permafrost thaw will be smaller than the cumulative anthropogenic emissions, yet still substantial on a global scale, with some experts comparing them to emissions caused by [[deforestation]].<ref name="Schuur2022" /> The [[IPCC Sixth Assessment Report]] estimates that carbon dioxide and methane released from permafrost could amount to the equivalent of 14–175&nbsp;billion tonnes of carbon dioxide per {{convert|1|C-change|F-change}} of warming.<ref name="AR6_WG1_Chapter922" />{{rp|1237}} For comparison, by 2019, annual anthropogenic emissions of carbon dioxide alone stood around 40&nbsp;billion tonnes.<ref name="AR6_WG1_Chapter922" />{{rp|1237}} A major review published in the year 2022 concluded that if the goal of preventing {{convert|2|C-change|F-change}} of warming was realized, then the average annual permafrost emissions throughout the 21st century would be equivalent to the year 2019 annual emissions of Russia. Under RCP4.5, a scenario considered close to the current trajectory and where the warming stays slightly below {{convert|3|C-change|F-change}}, annual permafrost emissions would be comparable to year 2019 emissions of Western Europe or the United States, while under the scenario of high global warming and worst-case permafrost feedback response, they would approach year 2019 emissions of China.<ref name="Schuur2022" />

Fewer studies have attempted to describe the impact directly in terms of warming. A 2018 paper estimated that if global warming was limited to {{convert|2|C-change|F-change}}, gradual permafrost thaw would add around {{convert|0.09|C-change|F-change}} to global temperatures by 2100,<ref>{{Cite journal |last1=Schellnhuber |first1=Hans Joachim |last2=Winkelmann |first2=Ricarda |last3=Scheffer |first3=Marten |last4=Lade |first4=Steven J. |last5=Fetzer |first5=Ingo |last6=Donges |first6=Jonathan F. |last7=Crucifix |first7=Michel |last8=Cornell |first8=Sarah E. |last9=Barnosky |first9=Anthony D. |author-link9=Anthony David Barnosky |date=2018 |title=Trajectories of the Earth System in the Anthropocene |journal=[[Proceedings of the National Academy of Sciences]] |volume=115 |issue=33 |pages=8252–8259 |bibcode=2018PNAS..115.8252S |doi=10.1073/pnas.1810141115 |issn=0027-8424 |pmc=6099852 |pmid=30082409 |doi-access=free}}</ref> while a 2022 review concluded that every {{convert|1|C-change|F-change}} of global warming would cause {{convert|0.04|C-change|F-change}} and {{convert|0.11|C-change|F-change}} from abrupt thaw by the year 2100 and 2300. Around {{convert|4|C-change|F-change}} of global warming, abrupt (around 50 years) and widespread collapse of permafrost areas could occur, resulting in an additional warming of {{convert|0.2-0.4|C-change|F-change}}.<ref name="ArmstrongMcKay2022" /><ref>{{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>

=== Thaw-induced ground instability ===
[[File:Permafrost coastal erosion USGS.png|thumb|Severe [[coastal erosion]] on the Arctic Ocean coast of [[Alaska]].]]
As the water drains or evaporates, soil structure weakens and sometimes becomes viscous until it regains strength with decreasing moisture content. One visible sign of permafrost degradation is the [[Drunken trees|random displacement of trees from their vertical orientation]] in permafrost areas.<ref>{{Cite book|last=Huissteden|first=J. van|url=https://books.google.com/books?id=mZPHDwAAQBAJ&q=permafrost+thaw|title=Thawing Permafrost: Permafrost Carbon in a Warming Arctic|date=2020|publisher=Springer Nature|isbn=978-3-030-31379-1|page=296 }}</ref> Global warming has been increasing permafrost slope disturbances and sediment supplies to fluvial systems, resulting in exceptional increases in river sediment.<ref>{{cite journal |last1=Li |first1=Dongfeng |last2=Lu |first2=Xixi |last3=Overeem |first3=Irina |last4=Walling |first4=Desmond E. |last5=Syvitski |first5=Jaia |last6=Kettner |first6=Albert J. |last7=Bookhagen |first7=Bodo |last8=Zhou |first8=Yinjun |last9=Zhang |first9=Ting |title=Exceptional increases in fluvial sediment fluxes in a warmer and wetter High Mountain Asia |journal=Science |date=29 October 2021 |volume=374 |issue=6567 |pages=599–603 |doi=10.1126/science.abi9649 |pmid=34709922 |bibcode=2021Sci...374..599L |s2cid=240152765 }}</ref> On the other hands, disturbance of formerly hard soil increases drainage of water reservoirs in northern [[wetland]]s. This can dry them out and compromise the survival of plants and animals used to the wetland ecosystem.<ref>{{Cite journal|last1=Koven|first1=Charles D.|last2=Riley|first2=William J.|last3=Stern|first3=Alex|date=2012-10-01|title=Analysis of Permafrost Thermal Dynamics and Response to Climate Change in the CMIP5 Earth System Models|journal=Journal of Climate|volume=26|issue=6|pages=1877–1900|doi=10.1175/JCLI-D-12-00228.1|osti=1172703 |url=http://www.escholarship.org/uc/item/9cv093s8|doi-access=free}}</ref>

In high mountains, much of the structural stability can be attributed to [[glacier]]s and permafrost.<ref>{{Cite journal |last1=Huggel |first1=C. |last2=Allen |first2=S. |last3=Deline |first3=P. |title=Ice thawing, mountains falling; are alpine rock slope failures increasing? |journal=Geology Today |volume=28 |issue=3 |pages=98–104 |date=June 2012 |doi=10.1111/j.1365-2451.2012.00836.x |bibcode=2012GeolT..28...98H |s2cid=128619284 }}</ref> As climate warms, permafrost thaws, decreasing slope stability and increasing stress through buildup of [[pore-water]] pressure, which may ultimately lead to slope failure and [[rockfall]]s.<ref>{{cite book|last1=Nater|first1=P.|last2=Arenson|first2=L.U.|last3=Springman|first3=S.M.|title=Choosing geotechnical parameters for slope stability assessments in alpine permafrost soils. In 9th international conference on permafrost.|date=2008|publisher=University of Alaska|location=Fairbanks, USA|isbn=978-0-9800179-3-9|pages=1261–1266}}</ref><ref name=Arnaud>{{Cite journal|last=Temme|first=Arnaud J. A. M.|date=2015|title=Using Climber's Guidebooks to Assess Rock Fall Patterns Over Large Spatial and Decadal Temporal Scales: An Example from the Swiss Alps|journal=Geografiska Annaler: Series A, Physical Geography |volume=97|issue=4|pages=793–807|doi=10.1111/geoa.12116|bibcode=2015GeAnA..97..793T |s2cid=55361904}}</ref> Over the past century, an increasing number of alpine rock slope failure events in mountain ranges around the world have been recorded, and some have been attributed to permafrost thaw induced by climate change. The 1987 [[Val Pola landslide]] that killed 22 people in the [[Italian Alps]] is considered one such example.<ref>{{Cite journal|last1=F.|first1=Dramis|last2=M.|first2=Govi|last3=M.|first3=Guglielmin|last4=G.|first4=Mortara|date=1995-01-01|title=Mountain permafrost and slope instability in the Italian Alps: The Val Pola Landslide|journal=Permafrost and Periglacial Processes|volume=6|issue=1|doi=10.1002/ppp.3430060108 |pages=73–81|bibcode=1995PPPr....6...73D }}</ref> In 2002, massive rock and ice falls (up to 11.8&nbsp;million m3), earthquakes (up to 3.9 [[Richter scale|Richter]]), floods (up to 7.8&nbsp;million m3 water), and rapid rock-ice flow to long distances (up to 7.5&nbsp;km at 60&nbsp;m/s) were attributed to slope instability in high mountain permafrost.<ref>{{cite book |doi=10.1130/REG15 |title=Catastrophic Landslides: Effects, Occurrence, and Mechanisms |series=Reviews in Engineering Geology |year=2002 |volume=15 |isbn=0-8137-4115-7 }}</ref>
[[File:Permafrost in Herschel Island 001.jpg|thumb|left|Thawing permafrost in [[Herschel Island]], Canada, 2013.]]
Permafrost thaw can also result in the formation of frozen debris lobes (FDLs), which are defined as "slow-moving landslides composed of soil, rocks, trees, and ice".<ref name="UAF FDLs 2022">{{Cite web| title = FDL: Frozen Debris Lobes | date = 7 January 2022| access-date = 7 January 2022 |series=FDLs |work=[[University of Alaska Fairbanks]]| url = https://fdlalaska.org/}}</ref> This is a notable issue in the [[Alaska]]'s southern [[Brooks Range]], where some FDLs measured over {{convert|100|metre|yards|abbr=on}} in width, {{convert|20|metre|yards|abbr=on}} in height, and {{convert|1000|metre|yards|abbr=on}} in length by 2012.<ref name="Daanen 2012">{{Cite journal | doi = 10.5194/nhess-12-1521-2012 | volume = 12 | pages = 1521–1537 | last1 = Daanen | first1 = Ronald | last2 = Grosse | first2 = Guido | last3 = Darrow | first3 = Margaret | last4 = Hamilton | first4 = T. | last5 = Jones
| first5 = Benjamin | title = Rapid movement of frozen debris-lobes: Implications for permafrost degradation and slope instability in the south-central Brooks Range, Alaska | journal = Natural Hazards and Earth System Sciences
| date = 21 May 2012| issue = 5 | bibcode = 2012NHESS..12.1521D | doi-access = free }}</ref><ref name="Darrow 2016">{{cite journal |last1=Darrow |first1=Margaret M. |last2=Gyswyt |first2=Nora L. |last3=Simpson |first3=Jocelyn M. |last4=Daanen |first4=Ronald P. |last5=Hubbard |first5=Trent D. |title=Frozen debris lobe morphology and movement: an overview of eight dynamic features, southern Brooks Range, Alaska |journal=The Cryosphere |date=12 May 2016 |volume=10 |issue=3 |pages=977–993 |doi=10.5194/tc-10-977-2016 |bibcode=2016TCry...10..977D |doi-access=free }}</ref> As of December 2021, there were 43 frozen debris lobes identified in the southern Brooks Range, where they could potentially threaten both the [[Trans Alaska Pipeline System]] (TAPS) corridor and the [[Dalton Highway]], which is the main transport link between the [[Interior Alaska]] and the [[Alaska North Slope]].<ref name="Hasemyer 2021">{{Cite web | last = Hasemyer| first = David| title = Unleashed by Warming, Underground Debris Fields Threaten to 'Crush' Alaska's Dalton Highway and the Alaska Pipeline | work = Inside Climate News | access-date = 7 January 2022| date = 20 December 2021| url = https://insideclimatenews.org/news/20122021/alaska-frozen-debris-lobes-dalton-highway-pipeline-climate-change/}}</ref>

==== Infrastructure ====
[[File:Hjort 2018 permafrost infrastructure.png|thumb|Map of likely risk to infrastructure from permafrost thaw expected to occur by 2050.<ref name="Hjort2018" />]]
As of 2021, there are 1162 settlements located directly atop the Arctic permafrost, which host an estimated 5 million people. By 2050, permafrost layer below 42% of these settlements is expected to thaw, affecting all their inhabitants (currently 3.3&nbsp;million people).<ref>{{Cite journal |last1=Ramage |first1=Justine |last2=Jungsberg |first2=Leneisja |last3=Wang |first3=Shinan |last4=Westermann |first4=Sebastian |last5=Lantuit |first5=Hugues |last6=Heleniak |first6=Timothy |date=6 January 2021 |title=Population living on permafrost in the Arctic |journal=Population and Environment |volume=43 |pages=22–38 |doi=10.1007/s11111-020-00370-6|s2cid=254938760 }}</ref> Consequently, a wide range of infrastructure in permafrost areas is threatened by the thaw.<ref name="Nelson2002">{{Cite journal|last1=Nelson|first1=F. E.|last2=Anisimov|first2=O. A.|last3=Shiklomanov|first3=N. I.|date=2002-07-01|title=Climate Change and Hazard Zonation in the Circum-Arctic Permafrost Regions|journal=Natural Hazards |volume=26|issue=3|pages=203–225|doi=10.1023/A:1015612918401|s2cid=35672358 }}</ref><ref>{{Cite book |last1=Barry |first1=Roger Graham |title=The global cryosphere past, present and future |last2=Gan |first2=Thian-Yew |date=2021 |isbn=978-1-108-48755-9 |edition=Second revised |location=Cambridge, United Kingdom |oclc=1256406954 |publisher=Cambridge University Press}}</ref>{{rp|236}} By 2050, it's estimated that nearly 70% of global infrastructure located in the permafrost areas would be at high risk of permafrost thaw, including 30–50% of "critical" infrastructure. The associated costs could reach tens of billions of dollars by the second half of the century.<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> Reducing [[greenhouse gas emissions]] in line with the [[Paris Agreement]] is projected to stabilize the risk after mid-century; otherwise, it'll continue to worsen.<ref name="Hjort2018" />

In [[Alaska]] alone, damages to infrastructure by the end of the century would amount to $4.6&nbsp;billion (at 2015 dollar value) if [[Representative Concentration Pathway|RCP8.5]], the high-emission [[climate change scenario]], were realized. Over half stems from the damage to buildings ($2.8&nbsp;billion), but there's also damage to roads ($700&nbsp;million), railroads ($620&nbsp;million), airports ($360&nbsp;million) and [[pipeline transport|pipelines]] ($170&nbsp;million).<ref name="Melvin2016">{{Cite journal |last1=Melvin|first1=April M.|last2=Larsen|first2=Peter|last3=Boehlert|first3=Brent |last4=Neumann|first4=James E.|last5=Chinowsky|first5=Paul|last6=Espinet|first6=Xavier|last7=Martinich|first7=Jeremy|last8=Baumann |first8=Matthew S.|last9=Rennels|first9=Lisa|last10=Bothner|first10=Alexandra|last11=Nicolsky|first11=Dmitry J.|last12=Marchenko |first12=Sergey S. |date=26 December 2016 |title=Climate change damages to Alaska public infrastructure and the economics of proactive adaptation |journal=Proceedings of the National Academy of Sciences |volume=114 |issue=2 |pages=E122–E131 |doi=10.1073/pnas.1611056113 |pmid=28028223 |pmc=5240706 |doi-access=free }}</ref> Similar estimates were done for RCP4.5, a less intense scenario which leads to around {{convert|2.5|C-change|F-change}} by 2100, a level of warming similar to the current projections.<ref name="CAT">{{cite web |url=https://climateactiontracker.org/global/cat-thermometer/ |title=The CAT Thermometer |access-date=25 April 2023}}</ref> In that case, total damages from permafrost thaw are reduced to $3&nbsp;billion, while damages to roads and railroads are lessened by approximately two-thirds (from $700 and $620&nbsp;million to $190 and $220&nbsp;million) and damages to pipelines are reduced more than ten-fold, from $170&nbsp;million to $16&nbsp;million. Unlike the other costs stemming from climate change in Alaska, such as damages from increased [[precipitation]] and flooding, [[climate change adaptation]] is not a viable way to reduce damages from permafrost thaw, as it would cost more than the damage incurred under either scenario.<ref name="Melvin2016" />

In Canada, [[Northwest Territories]] have a population of only 45,000 people in 33 communities, yet permafrost thaw is expected to cost them $1.3&nbsp;billion over 75 years, or around $51&nbsp;million a year. In 2006, the cost of adapting [[Inuvialuit]] homes to permafrost thaw was estimated at $208/m2 if they were built at pile foundations, and $1,000/m2 if they didn't. At the time, the average area of a residential building in the territory was around 100&nbsp;m2. Thaw-induced damage is also unlikely to be covered by [[home insurance]], and to address this reality, territorial government currently funds Contributing Assistance for Repairs and Enhancements (CARE) and Securing Assistance for Emergencies (SAFE) programs, which provide long- and short-term forgivable loans to help homeowners adapt. It is possible that in the future, mandatory relocation would instead take place as the cheaper option. However, it would effectively tear the local [[Inuit]] away from their ancestral homelands. Right now, their average personal income is only half that of the median NWT resident, meaning that adaptation costs are already disproportionate for them.<ref>{{Cite web|url=https://www.thearcticinstitute.org/reducing-individual-costs-permafrost-thaw-damage-canada-arctic/ |last=Tsui|first=Emily |title=Reducing Individual Costs of Permafrost Thaw Damage in Canada's Arctic |date=March 4, 2021|website=The Arctic Institute}}</ref>

By 2022, up to 80% of buildings in some Northern Russia cities had already experienced damage.<ref name="Hjort2022" /> By 2050, the damage to residential infrastructure may reach $15&nbsp;billion, while total public infrastructure damages could amount to 132&nbsp;billion.<ref>{{cite journal |last1=Melnikov |first1=Vladimir |last2=Osipov |first2=Victor |last3=Brouchkov |first3=Anatoly V. |last4=Falaleeva |first4=Arina A. |last5=Badina |first5=Svetlana V. |last6=Zheleznyak |first6=Mikhail N. |last7=Sadurtdinov |first7=Marat R. |last8=Ostrakov |first8=Nikolay A. |last9=Drozdov |first9=Dmitry S. |last10=Osokin |first10=Alexei B. |last11=Sergeev |first11=Dmitry O. |last12=Dubrovin |first12=Vladimir A. |last13=Fedorov |first13=Roman Yu. |date=24 January 2022 |title=Climate warming and permafrost thaw in the Russian Arctic: potential economic impacts on public infrastructure by 2050 |journal=Natural Hazards |volume=112 |issue=1 |pages=231–251 |doi=10.1007/s11069-021-05179-6|bibcode=2022NatHa.112..231M |s2cid=246211747 }}</ref> This includes [[oil and gas]] extraction facilities, of which 45% are believed to be at risk.<ref name="Hjort2018">{{Cite journal |last1=Hjort |first1=Jan |last2=Karjalainen |first2=Olli |last3=Aalto |first3=Juha |last4=Westermann |first4=Sebastian |last5=Romanovsky |first5=Vladimir E. |last6=Nelson |first6=Frederick E. |last7=Etzelmüller |first7=Bernd |last8=Luoto |first8=Miska |date=11 December 2018 |title=Degrading permafrost puts Arctic infrastructure at risk by mid-century |journal=Nature Communications |volume=9 |issue=1 |page=5147 |doi=10.1038/s41467-018-07557-4 |pmid=30538247 |pmc=6289964 |bibcode=2018NatCo...9.5147H }}</ref>
[[File:Ran 2022 QTP Permafrost damages 2050.png|thumb|left|Detailed map of Qinghai–Tibet Plateau infrastructure at risk from permafrost thaw under the SSP2-4.5 scenario.<ref name="Ran2022" />]]
Outside of the Arctic, [[Qinghai–Tibet Plateau]] (sometimes known as "the Third Pole"), also has an extensive permafrost area. It is warming at twice the global average rate, and 40% of it is already considered "warm" permafrost, making it particularly unstable. Qinghai–Tibet Plateau has a population of over 10 million people – double the population of permafrost regions in the Arctic – and over 1&nbsp;million m2 of buildings are located in its permafrost area, as well as 2,631&nbsp;km of [[power line]]s, and 580&nbsp;km of railways.<ref name="Ran2022" /> There are also 9,389&nbsp;km of roads, and around 30% are already sustaining damage from permafrost thaw.<ref name="Hjort2022" /> Estimates suggest that under the scenario most similar to today, [[Shared Socioeconomic Pathways|SSP2-4.5]], around 60% of the current infrastructure would be at high risk by 2090 and simply maintaining it would cost $6.31&nbsp;billion, with adaptation reducing these costs by 20.9% at most. Holding the global warming to {{convert|2|C-change|F-change}} would reduce these costs to $5.65&nbsp;billion, and fulfilling the optimistic [[Paris Agreement]] target of {{convert|1.5|C-change|F-change}} would save a further $1.32&nbsp;billion. In particular, fewer than 20% of railways would be at high risk by 2100 under {{convert|1.5|C-change|F-change}}, yet this increases to 60% at {{convert|2|C-change|F-change}}, while under SSP5-8.5, this level of risk is met by mid-century.<ref name="Ran2022">{{Cite journal |last1=Ran |first1=Youhua |last2=Cheng |first2=Guodong |last3=Dong |first3=Yuanhong |last4=Hjort |first4=Jan |last5=Lovecraft |first5=Amy Lauren |last6=Kang |first6=Shichang |last7=Tan |first7=Meibao |last8=Li |first8=Xin |date=13 October 2022 |title=Permafrost degradation increases risk and large future costs of infrastructure on the Third Pole |journal=Communications Earth & Environment |volume=3 |issue=1 |page=238 |doi=10.1038/s43247-022-00568-6 |bibcode=2022ComEE...3..238R |s2cid=252849121 }}</ref>

==== Release of toxic pollutants ====
[[File:Langer 2023 thawed pollution.png|thumb|Graphical representation of leaks from various toxic hazards caused by the thaw of formerly stable permafrost.<ref name="Langer2023" />]]
For much of the 20th century, it was believed that permafrost would "indefinitely" preserve anything buried there, and this made deep permafrost areas popular locations for hazardous waste disposal. In places like Canada's [[Prudhoe Bay]] oil field, procedures were developed documenting the "appropriate" way to inject waste beneath the permafrost. This means that as of 2023, there are ~4500 industrial facilities in the Arctic permafrost areas which either actively process or store hazardous chemicals. Additionally, there are between 13,000 and 20,000 sites which have been heavily contaminated, 70% of them in Russia, and their pollution is currently trapped in the permafrost. About a fifth of both the industrial and the polluted sites (1000 and 2200–4800) are expected to start thawing in the future even if the warming does not increase from its 2020 levels. Only about 3% more sites would start thawing between now and 2050 under the climate change scenario consistent with the [[Paris Agreement]] goals, [[Representative Concentration Pathway|RCP2.6]], but by 2100, about 1100 more industrial facilities and 3500 to 5200 contaminated sites are expected to start thawing even then. Under the very high emission scenario RCP8.5, 46% of industrial and contaminated sites would start thawing by 2050, and virtually all of them would be affected by the thaw by 2100.<ref name="Langer2023">{{Cite journal |last1=Langer |first1=Morit |last2=Schneider von Deimling |first2=Thomas |last3=Westermann |first3=Sebastian |last4=Rolph |first4=Rebecca |last5=Rutte |first5=Ralph |last6=Antonova |first6=Sofia |last7=Rachold |first7=Volker |last8=Schultz |first8=Michael |last9=Oehme |first9=Alexander |last10=Grosse |first10=Guido |date=28 March 2023 |title=Thawing permafrost poses environmental threat to thousands of sites with legacy industrial contamination |journal=Nature Communications |volume=14 |issue=1 |page=1721 |doi=10.1038/s41467-023-37276-4 |pmid=36977724 |pmc=10050325 |bibcode=2023NatCo..14.1721L }}</ref> [[Organochlorine]]s and other [[persistent organic pollutant]]s are of a particular concern, due to their potential to repeatedly reach local communities after their re-release through [[biomagnification]] in fish. At worst, future generations born in the Arctic would enter life with weakened [[immune system]]s due to pollutants accumulating across generations.<ref name="Miner2021">{{Cite journal |last1=Miner |first1=Kimberley R. |last2=D'Andrilli |first2=Juliana |last3=Mackelprang |first3=Rachel |last4=Edwards |first4=Arwyn |last5=Malaska |first5=Michael J. |last6=Waldrop |first6=Mark P. |last7=Miller |first7=Charles E. |date=30 September 2021 |title=Emergent biogeochemical risks from Arctic permafrost degradation |journal=Nature Climate Change |volume=11 |issue=1 |pages=809–819 |doi=10.1038/s41558-021-01162-y |bibcode=2021NatCC..11..809M |s2cid=238234156 }}</ref>
[[File:Langer 2023 alaska distributions.png|thumb|left|Distribution of toxic substances currently located at various permafrost sites in Alaska, by sector. The number of fish skeletons represents the toxicity of each substance.<ref name="Langer2023" />]]
A notable example of pollution risks associated with permafrost was the [[2020 Norilsk oil spill]], caused by the collapse of [[diesel fuel]] storage tank at Norilsk-Taimyr Energy's [[thermal power plant]] No. 3. It spilled 6,000 tonnes of fuel into the land and 15,000 into the water, polluting [[Ambarnaya]], [[Daldykan]] and many smaller rivers on [[Taimyr Peninsula]], even reaching lake [[Pyasino]], which is a crucial water source in the area. [[State of emergency]] at the federal level was declared.<ref name=TASS>{{cite news |title=Diesel fuel spill in Norilsk in Russia's Arctic contained |url=https://tass.com/emergencies/1164423 |access-date=7 June 2020 |work=[[TASS]] |date=5 June 2020 |location=Moscow, Russia}}</ref><ref name="Seddon2020">{{Cite news |url=https://www.ft.com/content/fa9c20a0-2dad-4992-9686-0ec98b44faa8 |archive-url=https://ghostarchive.org/archive/20221210/https://www.ft.com/content/fa9c20a0-2dad-4992-9686-0ec98b44faa8 |archive-date=10 December 2022 |url-access=subscription |title=Siberia fuel spill threatens Moscow's Arctic ambitions |author=Max Seddon |work=[[Financial Times]] |date=4 June 2020}}</ref> The event has been described as the second-largest oil spill in modern Russian history.<ref name=nyt>{{citation |url=https://www.nytimes.com/2020/06/04/world/europe/russia-oil-spill-arctic.html |title=Russia Declares Emergency After Arctic Oil Spill |last=Nechepurenko |first=Ivan |work=[[New York Times]] |date=5 June 2020}}</ref><ref>{{cite news |last1=Antonova |first1=Maria |title=Russia Says Melting Permafrost Is Behind The Massive Arctic Fuel Spill |url=https://www.sciencealert.com/russia-claims-melting-permafrost-is-behind-the-massive-arctic-fuel-spill |access-date=19 July 2020 |agency=Science Daily |date=5 June 2020}}</ref>

Another issue associated with permafrost thaw is the release of natural [[mercury (element)|mercury]] deposits. An estimated 800,000 tons of mercury are frozen in the permafrost soil. According to observations, around 70% of it is simply taken up by vegetation after the thaw.<ref name="Miner2021" /> However, if the warming continues under RCP8.5, then permafrost emissions of mercury into the [[atmosphere]] would match the current global emissions from all human activities by 2200. Mercury-rich soils also pose a much greater threat to humans and the environment if they thaw near rivers. Under RCP8.5, enough mercury will enter the [[Yukon River]] basin by 2050 to make its fish unsafe to eat under the [[EPA]] guidelines. By 2100, mercury concentrations in the river will double. Contrastingly, even if mitigation is limited to RCP4.5 scenario, mercury levels will increase by about 14% by 2100, and will not breach the EPA guidelines even by 2300.<ref name="Schaefer2020">{{Cite journal |last1=Schaefer |first1=Kevin |last2=Elshorbany |first2=Yasin |last3=Jafarov |first3=Elchin |last4=Schuster |first4=Paul F. |last5=Striegl |first5=Robert G. |last6=Wickland |first6=Kimberly P. |last7=Sunderland |first7=Elsie M. |date=16 September 2020 |title=Potential impacts of mercury released from thawing permafrost |journal=Nature Communications |volume=11 |issue=1 |page=4650 |doi=10.1038/s41467-020-18398-5 |pmid=32938932 |pmc=7494925 |bibcode=2020NatCo..11.4650S }}</ref>

=== Revival of ancient organisms ===
==== Microorganisms ====
{{Main|Pathogenic microorganisms in frozen environments}}
[[File:Alempic 2023 permafrost viruses.jpg|thumb|left|Some of the ancient amoeba-eating viruses revived by the research team of Jean-Michel Claverie. Clockwise from the top: ''Pandoravirus yedoma''; ''Pandoravirus mammoth'' and ''Megavirus mammoth''; ''Cedratvirus lena''; ''Pithovirus mammoth''; ''Megavirus mammoth''; ''Pacmanvirus lupus''.<ref name="Alempic2023" />]]

Bacteria are known for being able to [[Dormancy#Bacteria|remain dormant]] to survive adverse conditions, and [[viruses]] are not metabolically active outside of host cells in the first place. This has motivated concerns that permafrost thaw could free previously unknown microorganisms, which may be capable of infecting either humans or important livestock and [[crops]], potentially resulting in damaging epidemics or [[pandemic]]s.<ref name="Alempic2023">{{Cite journal|last1=Alempic|first1=Jean-Marie|last2=Lartigue|first2=Audrey |last3=Goncharov|first3=Artemiy|last4=Grosse|first4=Guido|last5=Strauss |first5=Jens|last6=Tikhonov|first6=Alexey N. |last7=Fedorov|first7=Alexander N.|last8=Poirot|first8=Olivier|last9=Legendre|first9=Matthieu |last10=Santini|first10=Sébastien |last11=Abergel|first11=Chantal |last12=Claverie |first12=Jean-Michel |date=18 February 2023|title=An Update on Eukaryotic Viruses Revived from Ancient Permafrost |journal=Viruses|volume=15|issue=2|page=564 |doi=10.3390/v15020564 |pmid=36851778 |pmc=9958942 |doi-access=free}}</ref><ref name="Alund2023">{{Cite news|url=https://www.usatoday.com/story/news/health/2023/03/09/zombie-virus-frozen-permafrost-revived-after-50-000-years/11434218002/|title=Scientists revive 'zombie virus' that was frozen for nearly 50,000 years |first1=Natalie Neysa |last1=Alund |date=9 March 2023 |website=[[USA Today]] |access-date=2023-04-23}}</ref> Further, some scientists argue that [[horizontal gene transfer]] could occur between the older, formerly frozen bacteria, and modern ones, and one outcome could be the introduction of novel [[antibiotic resistance]] genes into the [[genome]] of current pathogens, exacerbating what is already expected to become a difficult issue in the future.<ref name="Sajjad2020">{{Cite journal|last1=Sajjad|first1=Wasim |last2=Rafiq |first2=Muhammad |last3=Din|first3=Ghufranud|last4=Hasan|first4=Fariha |last5=Iqbal|first5=Awais |last6=Zada|first6=Sahib|last7=Ali|first7=Barkat|last8=Hayat|first8=Muhammad |last9=Irfan|first9=Muhammad|last10=Kang|first10=Shichang |date=15 September 2020|title=Resurrection of inactive microbes and resistome present in the natural frozen world: Reality or myth? |journal=Science of the Total Environment|volume=735 |page=139275 |doi=10.1016/j.scitotenv.2020.139275|pmid=32480145 |bibcode=2020ScTEn.73539275S |doi-access=free}}</ref><ref name="Miner2021" />

At the same time, notable pathogens like [[influenza]] and [[smallpox]] appear unable to survive being thawed,<ref name="Doucleff2020">{{Cite web|url=https://www.npr.org/sections/goatsandsoda/2020/05/19/857992695/are-there-zombie-viruses-like-the-1918-flu-thawing-in-the-permafrost|title=Are There Zombie Viruses — Like The 1918 Flu — Thawing In The Permafrost? |first1=Michaeleen |last1=Doucleff |website=NPR.org |access-date=2023-04-23}}</ref> and other scientists argue that the risk of ancient microorganisms being both able to survive the thaw and to threaten humans is not scientifically plausible.<ref name="Yong2014">{{Cite news|url=https://www.nature.com/articles/nature.2014.14801/ |title=Giant virus resurrected from 30,000-year-old ice |first1=Ed |last1=Yong |date=3 March 2014 |website=[[Nature (magazine)|Nature]] |access-date=2023-04-24}}</ref> Likewise, some research suggests that antimicrobial resistance capabilities of ancient bacteria would be comparable to, or even inferior to modern ones.<ref name="Perron2015">{{Cite journal|last1=Perron|first1=Gabriel G.|last2=Whyte |first2=Lyle|last3=Turnbaugh|first3=Peter J.|last4=Goordial|first4=Jacqueline|last5=Hanage|first5=William P.|last6=Dantas|first6=Gautam |last7=Desai|first7=Michael M. Desai |date=25 March 2015|title=Functional Characterization of Bacteria Isolated from Ancient Arctic Soil Exposes Diverse Resistance Mechanisms to Modern Antibiotics |journal=PLOS ONE|volume=10 |issue=3 |pages=e0069533 |doi=10.1371/journal.pone.0069533 |pmid=25807523 |pmc=4373940 |bibcode=2015PLoSO..1069533P |doi-access=free}}</ref><ref name="Wu2022">{{Cite journal|last1=Wu|first1=Rachel|last2=Trubl|first2=Gareth|last3=Tas|first3=Neslihan |last4=Jansson|first4=Janet K.|date=15 April 2022|title=Permafrost as a potential pathogen reservoir|journal=One Earth |volume=5|issue=4|pages=351–360 |doi=10.1016/j.oneear.2022.03.010 |bibcode=2022OEart...5..351W |s2cid=248208195 }}</ref>

==== Plants ====
In 2012, Russian researchers proved that permafrost can serve as a natural repository for ancient life forms by reviving a sample of ''[[Silene stenophylla]]'' from 30,000-year-old tissue found in an [[Last Glacial Period|Ice Age]] squirrel burrow in the [[Siberian]] permafrost. This is the oldest plant tissue ever revived. The resultant plant was fertile, producing white flowers and viable seeds. The study demonstrated that living tissue can survive ice preservation for tens of thousands of years.<ref>{{Citation|last=Isachenkov|first=Vladimir|title=Russians revive Ice Age flower from frozen burrow|date=February 20, 2012|url=http://phys.org/news/2012-02-russians-revive-ice-age-frozen.html|newspaper=Phys.Org|archive-url=https://web.archive.org/web/20160424214832/http://phys.org/news/2012-02-russians-revive-ice-age-frozen.html|access-date=2016-04-26|archive-date=2016-04-24|url-status=live}}</ref>

== History of scientific research ==
[[File:Schuur 2022 permafrost carbon literature.jpeg|thumb|The annual number of scientific research papers published on the subject of permafrost carbon has grown from next to nothing around 1990 to around 400 by 2020.<ref name="Schuur2022" />]]

Between the middle of the 19th century and the middle of the 20th century, most of the literature on basic permafrost science and the engineering aspects of permafrost was written in Russian. One of the earliest written reports describing the existence of permafrost dates to [[1684]], when [[well]] excavation efforts in [[Yakutsk]] were stumped by its presence.<ref name="Chu2020" />{{rp|25}} A significant role in the initial permafrost research was played by [[Alexander von Middendorff]] (1815–1894) and [[Karl Ernst von Baer]], a [[Baltic German]] scientist at the [[University of Königsberg]], and a member of the [[St Petersburg Academy of Sciences]]. Baer began publishing works on permafrost starting from 1838, and is often considered the "founder of scientific permafrost research". Through his compilation and analysis of all available data on ground ice and permafrost, Baer laid the foundation for the modern permafrost terminology.<ref name="King-edt">{{cite journal |last1=King |first1=Lorenz |date=2001 |title=Materialien zur Kenntniss des unvergänglichen Boden-Eises in Sibirien, compiled by Baer in 1843 |url=http://geb.uni-giessen.de/geb/volltexte/2006/3649/pdf/BaerMaterialien-2001.pdf |journal=Berichte und Arbeiten aus der Universitätsbibliothek und dem Universitätsarchiv Giessen |language=german |volume=51 |pages=1–315 |access-date=2021-07-27}}</ref>

Baer is also known to have composed the world's first permafrost [[textbook]] in 1843, "materials for the study of the perennial ground-ice", written in his native language. However, it was not printed at the time, and a Russian translation wasn't ready until 1942. The original German textbook was believed to be lost until the [[manuscript|typescript]] from 1843 was discovered in the library archives of the [[University of Giessen]]. The 234-page text was made available online, with additional maps, [[preface]] and comments.<ref name="King-edt" /> Notably, Baer's southern limit of permafrost in [[Eurasia]] drawn in 1843 corresponds well with the actual southern limit verified by modern research.<ref name="Brown1997" /><ref name="King-edt" />

Beginning in 1942, [[Siemon William Muller]] delved into the relevant Russian literature held by the [[Library of Congress]] and the [[United States Geological Survey Library|U.S. Geological Survey Library]] so that he was able to furnish the government an engineering [[field guide]] and a technical report about permafrost by 1943.<ref name="Walker2010">{{cite journal |last=Walker |first=H. Jesse |date=December 2010 |title=''Frozen in Time. Permafrost and Engineering Problems'' Review |journal=[[Arctic (journal)|Arctic]] |volume=63 |issue=4 |page=477 |doi=10.14430/arctic3340 |doi-access=free}}</ref> That report coined the English term as a contraction of permanently frozen ground,<ref name="USGSRay">{{cite web |last=Ray |first=Luis L. |title=Permafrost – USGS (United States Geological Survey) Library Publications Warehouse |url=https://pubs.usgs.gov/gip/70039262/report.pdf |url-status=live |archive-url=https://web.archive.org/web/20170502040613/https://pubs.usgs.gov/gip/70039262/report.pdf |archive-date=2017-05-02 |access-date=November 19, 2018}}</ref> in what was considered a direct translation of the Russian term ''{{lang|ru|vechnaia merzlota}}'' ({{lang-ru|link=no|вечная мерзлота}}). In 1953, this translation was criticized by another USGS researcher Inna Poiré, as she believed the term had created unrealistic expectations about its stability:<ref name="Chu2020">{{cite book |last=Chu |first=Pei-Yi |title=The Life of Permafrost: A History of Frozen Earth in Russian and Soviet Science |publisher=[[University of Toronto]] Press |date=2020 |jstor=10.3138/j.ctv1bzfp6j |isbn=978-1-4875-1424-2 |url=https://www.jstor.org/stable/10.3138/j.ctv1bzfp6j }}</ref>{{rp|3}} more recently, some researchers have argued that "perpetually refreezing" would be a more suitable translation.<ref>{{cite journal |last1=Peskoe-Yang |first1=Lynne |title=An ode to Arctic permafrost |journal=Science |volume=379 |issue=6639 |date=30 March 2023 |pages=380–383 |pmid=12532013 |doi=10.1126/science.adf6999 |bibcode=2023Sci...379.1306P |s2cid=257836768 }}</ref> The report itself was classified (as U.S. Army. Office of the Chief of Engineers, ''Strategic Engineering Study'', no. 62, 1943),<ref name="USGSRay" /><ref name="USGS1943">{{cite journal |author1=[[United States Geological Survey|U.S. Geological Survey]] |author2=[[United States Army Corps of Engineers]] |author3=[[Military Intelligence Division (United States)|Strategic Intelligence Branch]] |year=1943 |title=Permafrost or permanently frozen ground and related engineering problems |journal=Strategic Engineering Study |issue=62 |pages=231 |oclc=22879846}}</ref> until a revised version was released in 1947, which is regarded as the first North American treatise on the subject.<ref name="Walker2010" /><ref name="Muller1947">{{cite book |last=Muller |first=Siemon William |url=https://books.google.com/books?id=wQQhAAAAMAAJ |title=Permafrost. Or, Permanently Frozen Ground and Related Engineering Problems |publisher=Edwards |year=1947 |isbn=978-0-598-53858-1 |location=[[Ann Arbor, Michigan]] |oclc=1646047}}</ref>

Between 11 and 15 November 1963, the First International Conference on Permafrost took place on the grounds of [[Purdue University]] in the American town of [[West Lafayette, Indiana]]. It involved 285 participants (including "engineers, manufacturers and builders" who attended alongside the researchers) from a range of countries ([[Argentina]], [[Austria]], Canada, Germany, Great Britain, Japan, [[Norway]], [[Poland]], Sweden, Switzerland, the US and the [[USSR]]). This marked the beginning of modern scientific collaboration on the subject. Conferences continue to take place every five years. During the Fourth conference in 1983, a special meeting between the "Big Four" participant countries (US, USSR, China and Canada) had officially created the [[International Permafrost Association]].<ref>{{cite web |title=History |url=https://www.permafrost.org/history/ |publisher=[[International Permafrost Association]] |access-date=14 August 2023}}</ref>

In the recent decades, permafrost research has attracted more attention than ever due to the role it plays in [[climate change]]. Consequently, there has been a massive acceleration in published [[scientific literature]]. Around 1990, almost no papers were released containing the words "permafrost" and "carbon": by 2020, around 400 such papers were published every year.<ref name="Schuur2022" />

[[File:K.E.vonBaer 1840 03.jpg|thumb|center|upright=1.2|Southern limit of permafrost in [[Eurasia]] according to [[Karl Ernst von Baer]] (1843), and other authors.]]

== References ==
{{Reflist}}

==Sources==

* {{citation
 | year=2013
 | author=IPCC AR5 WG1
 | editor=Stocker, T.F.| title=Climate Change 2013: The Physical Science Basis. Working Group 1 (WG1) Contribution to the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5)
 | url=http://archive.ipcc.ch/report/ar5/wg1/
 | publisher=Cambridge University Press
|display-editors=etal}}. [http://www.climatechange2013.org/ Climate Change 2013 Working Group 1 website.]
* {{Cite book  |ref= {{harvid|IPCC AR6 WG1|2021}}
 |author= IPCC |author-link= IPCC
 |year= 2021
 |title= Climate Change 2021: The Physical Science Basis
 |series= Contribution of Working Group I to the [[IPCC Sixth Assessment Report|Sixth Assessment Report]] of the Intergovernmental Panel on Climate Change
 |display-editors= 4
 |editor1-first= V.     |editor1-last= Masson-Delmotte
 |editor2-first= P.     |editor2-last= Zhai
 |editor3-first= A. |editor3-last= Pirani
 |editor4-first= S. L.  |editor4-last= Connors
 |editor5-first= C.     |editor5-last= Péan
 |editor6-first= S.     |editor6-last= Berger
 |editor7-first= N.     |editor7-last= Caud
 |editor8-first= Y.     |editor8-last= Chen
 |editor9-first= L.     |editor9-last= Goldfarb
 |editor10-first= M. I. |editor10-last= Gomis
 |publisher= Cambridge University Press (In Press)
 |place= 
 |isbn= 
 |url= https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf
}}

== External links ==
{{Wiktionary}}
{{Commons category}}
* [http://cenperm.ku.dk/ Center for Permafrost]
* [https://www.permafrost.org/ International Permafrost Association (IPA)]
* [https://pleistocenepark.de/en/ Pleistocene & Permafrost Foundation]
* [http://pubs.usgs.gov/pp/p1386a/gallery5-fig04b.html Map of permafrost in Antarctica.]
* [https://www.youtube.com/watch?v=lxixy1u8GjY Permafrost – what is it? – Alfred Wegener Institute YouTube video]

{{Periglacial environment}}
{{Geotechnical engineering}}
{{Climate change}}
{{Portal bar|Geography|Alaska|Canada|Siberia}}
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[[Category:Permafrost| ]]
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[[Category:Cryosphere]]
[[Category:Geography of the Arctic]]
[[Category:Geomorphology]]
[[Category:Montane ecology]]
[[Category:Patterned grounds]]
[[Category:Pedology]]
[[Category:Periglacial landforms]]

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