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Permafrost is soil or underwater sediment which continuously remains below 0 °C (32 °F) for two or more years. Land-based permafrost can include the surface layer of the soil, but if the surface is too warm, it may still occur within a few centimeters of the surface down to hundreds of meters. It usually consists of ice holding in place a combination of various types of soil, sand, and rock, though in ice-free ground, perennially frozen non-porous bedrock can serve the same role.
Glaciology is the scientific study of glaciers, or more generally ice and natural phenomena that involve ice.
Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. Talus deposits typically have a concave upwards form, where the maximum inclination corresponds to the angle of repose of the mean debris particle size. The exact definition of scree in the primary literature is somewhat relaxed, and it often overlaps with both talus and colluvium.
Bolshoy Lyakhovsky Island, or Great Lyakhovsky, is the largest of the Lyakhovsky Islands belonging to the New Siberian Islands archipelago between the Laptev Sea and the East Siberian Sea in northern Russia. It has an area of 5,156.6 km2 (1,991.0 sq mi), and a maximum altitude of 311 m (1,020 ft).
In geology, a hummock is a small knoll or mound above ground. They are typically less than 15 meters (50 ft) in height and tend to appear in groups or fields. Large landslide avalanches that typically occur in volcanic areas are responsible for formation of hummocks. From the initiation of the landslide to the final formation, hummocks can be characterized by their evolution, spatial distribution, and internal structure. As the movement of landslide begins, the extension faulting results in formation of hummocks with smaller ones at the front of the landslide and larger ones in the back. The size of the hummocks is dependent on their position in the initial mass. As this mass spreads, the hummocks further modify to break up or merge to form larger structures. It is difficult to make generalizations about hummocks because of the diversity in their morphology and sedimentology. An extremely irregular surface may be called hummocky.
Carnobacterium pleistocenium is a recently discovered bacterium from the arctic part of Alaska. It was found in permafrost, seemingly frozen there for 32,000 years. Melting the ice, however, brought these extremophiles back to life. This is the first case of an organism "coming back to life" from ancient ice. These bacterial cells were discovered in a tunnel dug by the Army Corps of Engineers in the 1960s to allow scientists to study the permafrost in preparation for the construction of the Trans-Alaska pipeline system.
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 ground freezes and expands. Once temperatures reach −17 degrees Celsius or lower, the ice that has already formed acts like a solid and expands to form cracks in the surface known as ice wedges. As this process continues over many years ice wedges can grow, up to the size of a swimming pool. Ice wedges usually appear in a polygonal pattern known as ice wedge polygons. The cracks can also be filled with materials other than ice, especially sand, and are then called sand wedges.
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 soil will remain more stable than that at the surface, where the influence of the ambient temperature is greatest. This means that, over many years, the influence of cooling in winter and heating in summer will decrease as depth increases.
The Wegener–Bergeron–Findeisen process, is a process of ice crystal growth that occurs in mixed phase clouds in regions where the ambient vapor pressure falls between the saturation vapor pressure over water and the lower saturation vapor pressure over ice. This is a subsaturated environment for liquid water but a supersaturated environment for ice resulting in rapid evaporation of liquid water and rapid ice crystal growth through vapor deposition. If the number density of ice is small compared to liquid water, the ice crystals can grow large enough to fall out of the cloud, melting into rain drops if lower level temperatures are warm enough.
Pingos are intrapermafrost ice-cored hills, 3–70 m (10–230 ft) high and 30–1,000 m (98–3,281 ft) in diameter. They are typically conical in shape and grow and persist only in permafrost environments, such as the Arctic and subarctic. A pingo is a periglacial 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 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.
The Cold Regions Research and Engineering Laboratory (CRREL) is a United States Army Corps of Engineers, Engineer Research and Development Center research facility headquartered in Hanover, New Hampshire, that provides scientific and engineering support to the U.S. government and its military with a core emphasis on cold environments. CRREL also provides technical support to non-government customers.
Aufeis is a sheet-like mass of layered ice that forms from successive flows of ground or river water during freezing temperatures. This form of ice is also called overflow, icings, or the Russian term, naled. The term "Aufeis" was first used in 1859 by Alexander von Middendorff following his observations of the phenomenon in northern Siberia.
The International Permafrost Association (IPA), founded in 1983, is an international professional body formed to foster the dissemination of knowledge concerning permafrost and to promote cooperation among individuals and national or international organisations engaged in scientific investigation and engineering work related to permafrost and seasonally frozen ground. The IPA became an Affiliated Organisation of the International Union of Geological Sciences in July 1989.
The Itkillik River is a 220-mile (350 km) tributary of the Colville River in the North Slope Borough of the U.S. state of Alaska. The river flows northeast then northwest out of the Endicott Mountains near Oohlah Pass to meet the larger stream about 25 miles (40 km) southwest of Harrison Bay on the Beaufort Sea. An Iñupiaq map, drawn in about 1900, identifies the river as It-kil-lik, meaning Indian.
Drunken trees, tilted trees, or a drunken forest, is a stand of trees rotated from their normal vertical alignment.
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 surface. This leads to the accumulation of large amounts of snow around them. The summits of the palsas are free of snow even in winter, because the wind carries the snow and deposits on the slopes and elsewhere on the flat mire surface. Palsas can be up to 150 m in diameter and can reach a height of 12 m.
A frost boil, also known as mud boils, a stony earth circles, frost scars, or mud circles, are small circular mounds of fresh soil material formed by frost action and cryoturbation. They are found typically found in periglacial or alpine environments where permafrost is present, and may damage roads and other man-made structures. They are typically 1 to 3 metres in diameter.
The permafrost carbon cycle or Arctic carbon cycle is a sub-cycle of the larger global carbon cycle. Permafrost is defined as subsurface material that remains below 0o C for at least two consecutive years. Because permafrost soils remain frozen for long periods of time, they store large amounts of carbon and other nutrients within their frozen framework during that time. Permafrost represents a large carbon reservoir that is seldom considered when determining global terrestrial carbon reservoirs. Recent and ongoing scientific research however, is changing this view.
Cryosuction is the concept of negative pressure in freezing soil resulting from transformation of liquid water to ice in the soil pores whereby water migrates through soil pores to the freezing zone . Fine-grained soils such as clays and silts enables greater negative pressures than more coarse-grained soils due to the smaller pore size. In periglacial environments, this mechanism is highly significant and it is the predominant process in ice lens formation in permafrost areas. Several models for ice-lens formation by cryosuction exist, among others the Hydrodynamic model and the Pre-melting model, many of them based on the Clausius–Clapeyron relation with various assumptions, yielding cryosuction potentials of 11 to 12 atm per degree Celsius below zero depending on pore size.
Ground freezing is a construction technique used in circumstances where soil needs to be stabilized so it will not collapse next to excavations, or to prevent contaminants spilled into soil from being leached away. Ground freezing has been used for at least one hundred years.
References
- 1 2 3 French, Hugh M. (2017-10-27). The Periglacial Environment. John Wiley & Sons. ISBN 9781119132790.
- ↑ Lunardini, Virgil (1995). Permafrost Formation Time. Hanover, NH: US Army Corps of Engineers. pp. 12–3. ISBN 9781428914537.
- ↑ Bray, M.T.; French, H.M.; Shur, Y.L. (2005). "Lythostratigraphic mapping of syngenetic permafrost in the CRREL permafrost tunnel, Fairbanks, Alaska". 2nd European Conference on Permafrost: June 12-June 16, 2005, Potsdam, Germany : programme abstracts. GeoUnion Alfred-Wegener-Stiftlung. p. 56.
