![Mackenzie Delta, Pingo, Tuktoyaktuk](https://upload.wikimedia.org/wikipedia/commons/9/96/Mackenzie_Delta%2C_Pingo%2C_Tuktoyaktuk.jpg)
Pingos are intrapermafrost ice-cored hills, high and in diameter.
They are typically conical in shape and grow and persist only in
permafrost
Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface ...
environments, such as the
Arctic
The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...
and
subarctic
The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Generally, ...
.
A pingo is a
periglacial
Periglaciation (adjective: "periglacial", also referring to places at the edges of glacial areas) describes geomorphic processes that result from seasonal thawing of snow in areas of permafrost, the runoff from which refreezes in ice wedges and ot ...
landform, which is defined as a non-glacial landform or process linked to colder climates.
It is estimated that there are more than 11,000 pingos on Earth. The
Tuktoyaktuk
Tuktoyaktuk , or ''Tuktuyaaqtuuq'' (Inuvialuktun: ''it looks like a caribou''), is an Inuvialuit hamlet located in the Inuvik Region of the Northwest Territories, Canada, at the northern terminus of the Inuvik–Tuktoyaktuk Highway.Montgomery, ...
peninsula area has the greatest concentration of pingos in the world with a total of 1,350 pingos.
There is currently remarkably limited data on pingos.
History
![Mackenzie Delta, Pingo, Tuktoyaktuk (3)](https://upload.wikimedia.org/wikipedia/commons/2/2f/Mackenzie_Delta%2C_Pingo%2C_Tuktoyaktuk_%283%29.jpg)
In 1825,
John Franklin
Sir John Franklin (16 April 1786 – 11 June 1847) was a British Royal Navy officer and Arctic explorer. After serving in wars against Napoleonic France and the United States, he led two expeditions into the Canadian Arctic and through ...
made the earliest description of a pingo when he climbed a small pingo on Ellice Island in the
Mackenzie Delta.
However, it was in 1938 that the term ''pingo'' was first borrowed from the
Inuvialuit
The Inuvialuit (sing. Inuvialuk; ''the real people'') or Western Canadian Inuit are Inuit who live in the western Canadian Arctic region. They, like all other Inuit, are descendants of the Thule who migrated eastward from Alaska
Alask ...
by the Arctic botanist
Alf Erling Porsild in his paper on Earth mounds of the western Arctic coast of Canada and Alaska. Porsild Pingo in
Tuktoyaktuk
Tuktoyaktuk , or ''Tuktuyaaqtuuq'' (Inuvialuktun: ''it looks like a caribou''), is an Inuvialuit hamlet located in the Inuvik Region of the Northwest Territories, Canada, at the northern terminus of the Inuvik–Tuktoyaktuk Highway.Montgomery, ...
is named in his honour.
The term pingos, which in
Inuvialuktun
Inuvialuktun (part of ''Western Canadian Inuit/Inuktitut/Inuktut/Inuktun'') comprises several Inuit language varieties spoken in the northern Northwest Territories by Canadian Inuit who call themselves ''Inuvialuit''. Some dialects and sub-dialec ...
means conical hill, has now been accepted as a scientific term in English-language literature.
Formation
Pingos can only form in a permafrost environment. Evidence of collapsed pingos in an area suggests that there was once permafrost. Pingos that collapse (due to melting of the supporting ice) are called "ognips" ("pingos" spelled backwards).
Hydrostatic pingos
![Closed pingos diagram](https://upload.wikimedia.org/wikipedia/commons/d/d0/Closed_pingos_diagram.jpg)
Closed systems, also known as hydrostatic pingos are formed as a result of
hydrostatic pressure
Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body "fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an imme ...
that has built up within the core of pingos due to water.
They occur in regions of
continuous permafrost
Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface ...
where there is an impermeable ground layer.
These pingos are found in flat, poorly drained areas with limited groundwater available such as shallow lakes and river deltas.
The formation of these landforms occurs when layers of permafrost generate an upwards movement or pressure, resulting in masses of confined soil freezing, which pushes material upwards due to expansion.
The figure above illustrates this process and the changes that occur throughout the year.
This type of closed system pingos is formed in an area where a lake has been infilled with sediment. This indicates that the ground is insulated, allowing liquid water to collect underneath the sediment.
In winter months this sediment begins to freeze which leads to expansion of sediment, confining the water and increasing the pressure.
This results in the formation of a mound due to the upwards pressure. However, during summer months the ice core of the pingo begins to melt which causes the mound to cave in.
Hydraulic pingos
![Pingos](https://upload.wikimedia.org/wikipedia/commons/2/25/Pingos.png)
Hydraulic (open-system) pingos result from groundwater flowing from an outside source, i.e. sub-permafrost or intra-permafrost
aquifer
An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...
s. Hydrostatic pressure initializes the formation of the ice core as water is pushed up and subsequently freezes.
Open-system pingos have no limitations to the amount of water available unless the aquifers freeze. They often occur at the base of slopes and are commonly known as Greenland type.
The
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
is put under
artesian pressure and forces the ground up as it makes an expanding ice core.
It is not the artesian pressure itself that forces the ground up, but rather the ice core that is being fed the water from the aquifer. These are often formed in a thin, discontinuous permafrost. These conditions allow an ice core to form, but also provide it with a supply of artesian ground water. If water pressure entering an artesian pingo is strong enough, it can lift the pingo up allowing a sub-pingo water lens to form underneath. However, if the water lens starts to leak water it can cause subsidence which can compromise the structure.
These pingos are often oval or oblong shaped. It is still not entirely understood why open system or hydraulic pingos normally occur in unglaciated terrain.
Pingos usually grow only a couple of centimetres per year, with Ibyuk Pingo growing at a rate of a year,
and the largest take decades or even centuries to form. The process that creates pingos is believed to be closely related to
frost heaving
Frost heaving (or a frost heave) is an upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated in ...
. The base of the pingo tends to reach its maximum diameter in its early youth. This means pingos tend to grow higher rather than growing in diameter and height at the same time.
The height of pingos can range anywhere from and their diameters range from .
The shape of pingos in usually circular. Smaller pingos tend to have curved tops whereas larger pingos usually have collapsed mounds or craters due to the melting of exposed ice.
Locations
Greenland
The landscape of
Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...
contains many pingos and other glacial landforms. In western Greenland it is estimated that there are 29 pingos, whilst in eastern Greenland it is estimated there are 71 pingos. The majority of pingos in Greenland are located within
Disko Bay
Disko Bay ( kl, Qeqertarsuup tunua; da, DiskobugtenChristensen, N.O. & al.Elections in Greenland. ''Arctic Circular'', Vol. 4 (1951), pp. 83–85. Op. cit. "Northern News". ''Arctic'', Vol. 5, No. 1 (Mar 1952), pp. 58–59.) is a large ...
and
Nuussuaq Peninsula
Nuussuaq Peninsula (, old spelling: ''Nûgssuaq'') is a large (180x48 km) peninsula in western Greenland.
Geography
The waters around the peninsula are that of Baffin Bay. To the south and southwest the peninsula is bounded by Disko Bay, ...
within western Greenland as well as some in eastern Greenland in
Mesters Vig.
The thickness of the permafrost at Disko Bay is around deep, providing for ideal conditions for the development of closed system pingos. There are 20 pingos located on Disko Island, with the largest located on Kuganguaq alluvial plain at wide and high.
In eastern Greenland, pingos are found in
Nioghalvfjerdsfjorden
Nioghalvfjerdsfjorden is a fjord located in pee pee ederick VIII Land, in Northeast Greenland National Park of northeastern Greenland. It is located at latitude 79° N (hence the name, which in Danish means "the fjord of seventy-nine") between La ...
. They are well known because they are the northernmost pingos of eastern Greenland. The largest of these pingos is wide and high, taking the shape of a semicircle. This pingo is still active, meaning it is increasing in elevation over time.
Canada
Tuktoyaktuk Peninsula pingos
![Pingo in the Mackenzie delta area](https://upload.wikimedia.org/wikipedia/commons/8/89/Pingo_in_the_Mackenzie_delta_area.jpg)
The
Tuktoyaktuk
Tuktoyaktuk , or ''Tuktuyaaqtuuq'' (Inuvialuktun: ''it looks like a caribou''), is an Inuvialuit hamlet located in the Inuvik Region of the Northwest Territories, Canada, at the northern terminus of the Inuvik–Tuktoyaktuk Highway.Montgomery, ...
Peninsula is an area with a marine
tundra
In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless moun ...
environment on the shores of the
Arctic Ocean
The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...
in the
Northwest Territories
The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...
, Canada. This peninsula is covered in thick permafrost, which is known to be more than 50,000 years old. There are many pingos within the
Pingo Canadian Landmark
Pingo Canadian Landmark, also known as Pingo National Landmark, is a natural area protecting eight pingos near Tuktoyaktuk, Northwest Territories. It is in a coastal region of the Arctic Ocean which contains approximately 1,350 Arctic ice dome ...
area, all ranging in size and diameter. The most well known pingo in this area is Ibyuk Pingo, which is the tallest pingo in Canada. The height of this pingo is above sea level, but the pingo is still increasing in height by a few centimetres every year. This pingo is one of the younger pingos in the area, estimated at around 1,000 years old.
Since about 1990, several larger pingos have started to melt out as the injection ice of the core is exposed.
Alaska
![Melting pingo wedge ice](https://upload.wikimedia.org/wikipedia/commons/6/61/Melting_pingo_wedge_ice.jpg)
Approximately 80% of
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
is covered in permafrost, with 29% of this continuous permafrost, 35% discontinuous permafrost and the rest sporadic or isolated permafrost. Throughout Alaska, there are more than 1,500 known pingos with the majority being open system pingos.
The height of pingos in Alaska ranges from in height and in width. The world's tallest pingo is located in Alaska, known as the
Kadleroshilik Pingo. The Kadleroshilik Pingo is in height, but is continuing to rise in elevation by a few centimeters a year.
Siberia
In
Siberia
Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...
, an area containing a high density of close system pingos can be found near
Yakutsk
Yakutsk (russian: Якутск, p=jɪˈkutsk; sah, Дьокуускай, translit=Djokuuskay, ) is the capital city of the Sakha Republic, Russia, located about south of the Arctic Circle. Fueled by the mining industry, Yakutsk has become one of ...
located on the
Lena River
The Lena (russian: Ле́на, ; evn, Елюенэ, ''Eljune''; sah, Өлүөнэ, ''Ölüöne''; bua, Зүлхэ, ''Zülkhe''; mn, Зүлгэ, ''Zülge'') is the easternmost of the three great Siberian rivers that flow into the Arctic Ocean ...
. In this area there are more than 500 pingos next to the Lena River. The area consists of
alluvial plain
An alluvial plain is a largely flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms. A floodplain is part of the process, being the sma ...
s areas of thick permafrost, allowing pingos to form and develop.
Central Asia
Areas of
Central Asia
Central Asia, also known as Middle Asia, is a subregion, region of Asia that stretches from the Caspian Sea in the west to western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes t ...
are known to have pingos at the highest elevations in the world.
For example, the
Tibetan Plateau
The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the Ti ...
has pingos at above in elevation due to its permanently frozen terrain. This environment is perfect for pingo production, and the cold, dry permafrost along with cold temperatures deters pingo collapse.
Scandinavia
Despite its high latitude and the occurrence of permafrost, no modern pingos are known from
Scandinavia
Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...
.
Palsa
Palsas are peat mounds with a permanently frozen peat and mineral soil core. They are a typical phenomenon in the polar and subpolar zone of discontinuous permafrost. One of their characteristics is having steep slopes that rises above the mire ...
mounds in Scandinavia have been mistaken for pingos. Some depressions found in
Jutland
Jutland ( da, Jylland ; german: Jütland ; ang, Ēota land ), known anciently as the Cimbric or Cimbrian Peninsula ( la, Cimbricus Chersonesus; da, den Kimbriske Halvø, links=no or ; german: Kimbrische Halbinsel, links=no), is a peninsula of ...
, and some circular lakes in the
Finnmarksvidda
Finnmarksvidda ( sme, Finnmárkkoduottar; en, Finnmark plateau/highland) is Norway's largest plateau, with an area greater than . The plateau lies about above sea level. Approximately 36% of Finnmark lies on the Finnmarksvidda.
Geography
Fr ...
plateau may be remnants of collapsed pingos. The possible Jutland pingos could have developed during the
Weichselian glaciation
The Weichselian glaciation was the last glacial period and its associated glaciation in northern parts of Europe. In the Alpine region it corresponds to the Würm glaciation. It was characterized by a large ice sheet (the Fenno-Scandian ice sheet) ...
and the possible Finnmarkvidda pingos during
cold periods of the last
deglaciation Deglaciation is the transition from full glacial conditions during ice ages, to warm interglacials, characterized by global warming and sea level rise due to change in continental ice volume. Thus, it refers to the retreat of a glacier, an ice shee ...
.
Mars
Although no pingos have been confirmed to be located on
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...
, scholars agree that there are indisputable signs of pingo-like features (PLFs).
PLFs are periglacial features which have been discovered but are usually not classed as pingos. This is usually because they are not large enough to be classified as pingos, or there is not enough evidence to class them as pingos.
Effects of climate change
Global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
is causing
Arctic
The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...
temperatures to rapidly rise, causing
permafrost
Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface ...
to thaw. For this reason, permafrost environments are extremely vulnerable to
climate change in the Arctic
Major environmental issues caused by contemporary climate change in the Arctic region range from the well-known, such as the loss of sea ice or melting of the Greenland ice sheet, to more obscure, but deeply significant issues, such as permafr ...
. Permafrost degradation caused by climate warming is indicated by increased mean annual ground temperature, increased
active layer
In environments containing permafrost, the active layer is the top layer of soil that thaws during the summer and freezes again during the autumn. In all climates, whether they contain permafrost or not, the temperature in the lower levels of the ...
thickness,
talik
A talik is a layer of year-round unfrozen ground that lies in permafrost areas. In regions of continuous permafrost, taliks often occur underneath shallow thermokarst lakes and rivers, where the deep water does not freeze in winter and thus the ...
and
thermokarst
Thermokarst is a type of terrain characterised by very irregular surfaces of marshy hollows and small hummocks formed as ice-rich permafrost thaws. The land surface type occurs in Arctic areas, and on a smaller scale in mountainous areas such as ...
development and disappearance of permafrost islands. The interchange between permafrost degradation and aggradation shapes sub-Arctic and Arctic lowland landscapes, and therefore contain records of past climate and landscape development.
Pingos are vulnerable to surface disturbance given the considerable amount of ground ice stored within them. Abrupt permafrost thaw processes can cause
ice wedge
An ice wedge is a crack in the ground formed by a narrow or thin piece of ice that measures up to 3–4 meters in length at ground level and extends downwards into the ground up to several meters. During the winter months, the water in the gr ...
s within pingos to melt, which can result in increased pingo collapse and the formation of remnant lakes. However, there are currently few studies investigating how climate change could affect formation and growth of pingos.
See also
*
Gas hydrate pingo A gas hydrate pingo is a submarine dome structure formed by the accumulation of gas hydrates under the seafloor. Gas hydrate pingos resemble the pingo landforms found on land in periglacial regions.
Gas hydrate pingos may accumulate non-hydrate ga ...
- Submarine dome structure formed by the accumulation of
gas hydrates
Clathrate hydrates, or gas hydrates, clathrates, hydrates, etc., are crystalline water-based solids physically resembling ice, in which small non-polar molecules (typically gases) or polar molecules with large hydrophobic moieties are trapped i ...
under the seafloor that resembles a pingo
*
*
*, some are known as ''pingo ponds'' especially in Norfolk, England.
*
*, a low oval elevation in areas with
permafrost
Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface ...
, frequently
peat bog
A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; a ...
s, where a perennial ice lens has developed within the soil.
*
References
Bibliography
* Easterbrook, Don and O'Neill, W. Scott. (1999) ''Surface Processes and Landforms.'' Second Edition. 1999, 1993. Prentice-Hall, inc. p. 412-416.
*
External links
*
{{Periglacial environment
Geomorphology
Glaciology
Ground freezing
Palsas
Patterned grounds
Periglacial landforms
Soil
Geologic domes
Geography of the Arctic
Geography of the Inuvialuit Settlement Region