In geology, permafrost or permafrost soil is soil at or below the freezing point of water (0°C or 32°F) for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground material. Most permafrost is located in high latitudes (e.g. North and South poles), but alpine permafrost exists at high altitudes. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... Fahrenheit is a temperature scale named after the German physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ... Latitude, usually denoted symbolically by the Greek letter phi, , gives the location of a place on Earth north or south of the equator. ... Altitude is the elevation of an object from a known level or datum. ...

The extent of permafrost can vary as the climate changes. Today, approximately 20% of the Earth's land mass is covered by permafrost (including discontinuous permafrost) or glacial ice. Overlying permafrost is a thin layer of ground called the active layer that seasonally thaws during the summer. Plant life can be supported only within the active layer because growth can occur only in soil that is fully thawed for some part of the year. Thickness of the active layer varies by year and location but is typically 0.6–4 m (2 to 12 feet) thick. In areas of continuous permafrost and harsh winters the depth of the permafrost can be very great: 440m (1330 feet) at Barrow, Alaska, 600 m (1970 feet) at Prudhoe Bay, Alaska, up to 726 m (2382 feet) in the Canadian Arctic islands and as much as 1493 m (4510 feet) in the northern Lena and Yana River basins in Siberia. Variations in CO2, temperature and dust from the Vostok ice core over the last 400,000 years For current global climate change, see Global warming. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... Glacial and Glaciation redirect here. ... This does not cite its references or sources. ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta—liverworts Anthocerotophyta—hornworts Bryophyta—mosses Vascular plants (tracheophytes) †Rhyniophyta—rhyniophytes †Zosterophyllophyta—zosterophylls Lycopodiophyta—clubmosses †Trimerophytophyta—trimerophytes Pteridophyta—ferns and horsetails Seed plants (spermatophytes) †Pteridospermatophyta—seed ferns Pinophyta—conifers Cycadophyta—cycads Ginkgophyta—ginkgo Gnetophyta—gnetae Magnoliophyta—flowering plants... The or meter (see spelling differences) is a measure of length. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... Barrow is a city in North Slope Borough of the U.S. state of Alaska. ... Prudhoe Bay (IPA: ) is a census-designated place (CDP) located in North Slope Borough in the U.S. state of Alaska. ... Reference map of Canadian arctic islands. ... The Lena (Russian: Ле́на) in Siberia is the 10th longest river in the world and has the 9th largest watershed. ... The Yana River (Яна in Russian), a river in Sakha in Russia, located between the Lena to the west and the Indigirka to the east. ...

Continuous and discontinuous permafrost

Permafrost will typically form in any climate where the mean annual air temperature is less than the freezing point of water. Exceptions are found in moist-wintered forest climates, such as in Northern Scandinavia and North-Eastern Russia west of the Urals, where winter snow acts as an insulating blanket. The bottoms of glaciers can also be free of permafrost, even though this is not the most common situation. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Map of the Ural Mountains The Ural Mountains (Russian: , Uralskiye gory) (also known as the Urals, the Riphean Mountains in Greco-Roman antiquity, and known as the Stone Belt) are a mountain range that runs roughly north and south through western Russia. ...

Typically the temperature of the ground will be on average less variable from season to season than the air temperature, and temperatures also tend to increase with depth. Thus, if the mean annual air temperature is only slightly below 0°C (32°F), permafrost will form only in spots that are sheltered — usually with a northerly aspect. This creates what is known as discontinuous permafrost. Usually, permafrost will remain discontinuous in a climate where the mean annual soil surface temperature is between −5 and 0 °C (23 to 32°F). In the moist-wintered areas mentioned before, there may not be even discontinuous permafrost down to −2 °C. 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 −2˚ and −4˚C (28˚ and 25˚ F), and sporadic permafrost, where permafrost cover is less than 50 percent of the landscape and typically occurs at mean annual temperatures between 0˚ and −2˚C (32˚ and 28˚F). In geography, aspect generally refers to the direction to which a mountain slope faces. ...

In soil science, the sporadic permafrost zone is abbreviated to SPZ and the extensive discontinuous permafrost zone to DPZ.

There are exceptions in unglaciated Siberia and Alaska where the present depth of permafrost is a relic of climatic conditions during glacial ages where winters were up to 11°C (20°F) colder than those of today. At mean annual soil surface temperatures below −5°C (23°F) the influence of aspect can never be sufficient to thaw permafrost and a zone of continuous permafrost (abbreviated to CPZ) forms. There are also "fossil" cold anomalies in the Geothermal gradient in areas where deep permafrost developed during the Pleistocene that still persists down to several hundred metres. The Suwałki cold anomaly in Poland led to the recognition that similar thermal disturbances related to Pleistocene-Holocene climatic changes are recorded in boreholes throughout Poland. [1] It has been suggested that Western Siberia be merged into this article or section. ... Official language(s) none Capital Juneau Largest city Anchorage Area  Ranked 1st  - Total 663,267 sq mi (1,717,855 km²)  - Width 808 miles (1,300 km)  - Length 1,479 miles (2,380 km)  - % water 13. ... penis, hahaha big long penis. ...

A line of continuous permafrost in the Northern Hemisphere (Frozen Ground 28, 2004, p5) is formed from the furthest-northward points at which permafrost sometimes melts or is interrupted by regions without permafrost; north of this line all land is covered by permafrost or glacial ice. The "line" of continuous permafrost lies further north at some longitudes than others and can gradually move 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 if not all of the Antarctic continent is covered not with frozen soil but with glacial ice. The Northern Hemisphere is the half of a planets surface (or celestial sphere) that is north of the equator (the word hemisphere literally means half ball). On the Earth, the Northern Hemisphere contains most of the land and about 88-90% of the human population. ... Longitude, sometimes denoted by the Greek letter λ (lambda),[1][2] describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. ... southern hemisphere highlighted in yellow (Antarctica not depicted). ... For other uses, see Antarctica (disambiguation). ...

Permafrost extent

Polygons on the ground.

Measurement of the depth and extent of permafrost may be an indicator of global warming as recent years (1998 and 2001) have seen record thawing of permafrost in Alaska and Siberia. This thawing has led to stands of trees falling over, labelled drunken trees, due to insufficient rooting. In the Yukon, the zone of continuous permafrost has moved 100 kilometres poleward since 1899. However accurate records only go back 30 years. It is thought that the thawing of permafrost could exacerbate global warming through the release of methane and other hydrocarbons which are powerful greenhouse gases. It also could encourage erosion because permafrost lends considerable stability to the barren slopes in the Arctic. Image File history File links Polygon on the ground. ... Image File history File links Polygon on the ground. ... Global mean surface temperatures 1850 to 2006 Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 Global warming is the observed increase in the average temperature of the Earths atmosphere and oceans in recent decades and the projected... Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... Year 2001 (MMI) was a common year starting on Monday of the Gregorian calendar. ... This article or section is in need of attention from an expert on the subject. ... Year 1899 (MDCCCXCIX) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Friday [1] of the 12-day-slower Julian calendar). ... Methane is a chemical compound with the molecular formula CH4. ... Oil refineries are key to obtaining hydrocarbons; crude oil is processed through several stages to form desirable hydrocarbons, used in fuel and other commercial products. ... Greenhouse gases are gaseous components of the atmosphere that contribute to the greenhouse effect. ... Severe soil erosion in a wheat field near Washington State University, USA. For erosion as an operation of Mathematical morphology, see Erosion (morphology) Erosion is displacement of solids (soil, mud, rock and other particles) by the agents of ocean currents, wind, water, or ice by downward or down-slope movement...

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 and the Sea of Azov (then dry land) and China south to Beijing. 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. In the southern hemisphere, there is some evidence for former permafrost from this period in central Otago and Argentine Patagonia, but it was probably discontinuous. Temperature proxies for the last 40,000 years The Last Glacial Maximum refers to the time of maximum extent of the ice sheets during the last glaciation, approximately 21 thousand years ago. ... World map showing the location of Europe. ... Szeged and the Tisza river. ... The shallow Sea of Azov is clearly distinguished from the deeper Black Sea. ... Beijing (Chinese: 北京; pinyin: BÄ›ijÄ«ng; IPA: ;  ), a metropolis in northern China, is the capital of the Peoples Republic of China (PRC). ... World map showing North America A satellite composite image of North America. ... An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (19,305 mile²). The only current ice sheets are Antarctic and Greenland; during the last ice age at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much of Canada... It has been suggested that this article be split into multiple articles. ... This article is about the U.S. State. ... Official language(s) English Capital Jefferson City Largest city Kansas City Largest metro area Greater St. ... Otago (help· info) is one of the regions of New Zealand and lies in the south-east of the South Island. ... Patagonia, as most commonly defined (in orange). ...

Time to form deep permafrost

It has been calculated that the time required to form the deep permafrost underlying Prudhoe Bay, Alaska is 500,740 years. This time extends over several glacial and interglacial cycles of the Pleistocene and suggests that the present climate of Prudhoe Bay is probably considerably warmer than it has been on average over that period. Such warming over the past 15,000 years is widely accepted. [2] The table to the right shows that the first hundred metres of permafrost forms relatively quickly but that deeper levels take progressively longer. Prudhoe Bay (IPA: ) is a census-designated place (CDP) located in North Slope Borough in the U.S. state of Alaska. ... The Pleistocene epoch (IPA: ) is part of the geologic timescale. ...

Construction on permafrost

Building on permafrost is difficult due to the heat of the building (or pipeline) melting the permafrost and sinking downwards. This sinking problem has three common solutions: using foundations on wood piles, building on a thick gravel pad (usually 1 to 2 meters (about 4 to 5 feet) thick), or using anhydrous ammonia heat pipes. The Trans-Alaska Pipeline System uses insulated heat pipes to keep the pipeline from sinking into the permafrost. Qingzang railway in Tibet was built using a variety of methods to keep the ground cool. A foundation is a structure that transmits loads from a building or road to the underlying ground. ... Look up Pile in Wiktionary, the free dictionary. ... Gravel being unloaded from a barge Gravel is rock that is of a certain grain size range. ... Map of the pipeline The Trans-Alaska Pipeline System (TAPS), usually called the Alyeska Pipeline in Alaska or the Alaska Pipeline elsewhere, is a major U.S. oil pipeline connecting oil fields in northern Alaska to a sea port where the oil can be shipped to the Lower 48 states... Map of the railway The worlds highest railway which traverses the vast terrain of Tibet. ... Tibet (older spelling Thibet; Tibetan: བོད་; Wylie: Bod; Lhasa dialect IPA: [; Simplified and Traditional Chinese: 西藏, Hanyu Pinyin: XÄ«zàng; also referred to as 藏区 (Simplified Chinese), 藏區 (Traditional Chinese), ZàngqÅ« (Hanyu Pinyin), see Name section below) is a plateau region in Central Asia and the indigenous home to the Tibetan people. ...

At the Permafrost Research Institute in Yakutsk, it has been found that sinking of large buildings into the frozen earth (known to the Yakuts before Yakutsk was even founded) can be prevented effectively by means of stilts extended down to a depth of about fifteen metres or more. At this depth the temperature does not change with the seasons but remains at about -5°C. The tower of ostrog, or fort, in Yakutsk was constructed in 1683. ... Yakuts, self-designation: Sakha, are a Turkic people associated with the Sakha (Yakutia) Republic. ...

See also

International Permafrost Association The International Permafrost Association (IPA), founded in 1983, has as its objectives to foster the dissemination of knowledge concerning permafrost and to promote cooperation among persons and national or international organisations engaged in scientific investigation and engineering work related to permafrost and seasonally frozen ground. ...

Permafrost Young Researchers Network The Permafrost Young Researcher’s Network (PYRN) is a network formed in 2005 to formally facilitate and strengthen contacts among young scientists in the permafrost community. ...

External links

• What is Permafrost?, Geological Survey of Canada
• How rapidly is permafrost changing? What are the impacts of these changes? from *NOAA
• Melting Russian Permafrost Could Accelerate Global Warming - ENS (7 September 2006)
• Mike W. Smith's page on permafrost in Canada
• Earth's permafrost starts to squelch — BBC (29 December, 2004)
• PERMAFROST: A Building Problem For Alaska
• Permafrost Young Researchers Network (PYRN)
• International Permafrost Association (IPA)
• United States Permafrost Association (USPA)