Blue-ice area

Last updated

A blue-ice area in the Miller Range with a meteorite Miller Range, Antarctica - Meteorite (2).jpg
A blue-ice area in the Miller Range with a meteorite

A blue-ice area is an ice-covered area of Antarctica where wind-driven snow transport and sublimation result in net mass loss from the ice surface in the absence of melting, forming a blue surface that contrasts with the more common white Antarctic surface. Such blue-ice areas typically form when the movement of both air and ice are obstructed by topographic obstacles such as mountains that emerge from the ice sheet, generating particular climatic conditions where the net snow accumulation is exceeded by wind-driven sublimation and snow transports.

Contents

Only about 1% of Antarctic ice area can be considered to be blue-ice area, but they have attracted scientific interest due to the large numbers of meteorites that accumulate on them; these meteorites either fall directly on the blue-ice area and remain there, or they fall elsewhere into the ice sheet and are transported to the blue-ice area by ice flow. Additionally, ice up to 2.7 million years old has been obtained from blue-ice areas. Blue-ice areas are sometimes used as runways for aircraft.

Appearance

A glacier in the Transantarctic Mountains. Blue ice is seen as a lighter blue in the photograph, while the darker blue is formed by re-frozen melt ponds. Transantarctic pho 2017334 lrg.jpg
A glacier in the Transantarctic Mountains. Blue ice is seen as a lighter blue in the photograph, while the darker blue is formed by re-frozen melt ponds.

Blue-ice areas have a generally smooth and often [1] rippled appearance, a blue colour [2] and a sparseness of bubbles in the ice. [3] This light blue colour is a consequence of the absorption of light by ice and air bubbles encased within it, and is the source of the name "blue-ice area". It contrasts markedly with the white colour of Antarctic plains [4] and can be seen from space and from aerial images, [3] while the density of the blue ice makes it appear on radar images as a dark ice form. [5] Scalloped or rippled surfaces have almost regular surface patterns, although wholly smooth blue-ice areas exist as well, [6] and the terrain even of rippled surfaces features very low aerodynamic roughness, perhaps among the lowest of all permanent natural surfaces. [7] This is because most aerodynamic drag is caused by surface anomalies less than a centimetre long, not larger uneven forms. [6] Wave structures form through sublimation. [8]

The occurrence of supraglacial moraines at blue-ice areas has been reported; [9] these form when debris contained within a glacier accumulates at the surface due to melting or sublimation. [10] Small depressions in the ice known as cryoconite holes are common and are formed where rocks got embedded in the ice, [4] but are absent on more mountainous blue-ice areas. [11]

Typical blue-ice areas often feature intense katabatic winds, with average winds reaching 80 kilometres per hour (50 mph) and gusts of up to 200 kilometres per hour (120 mph); such winds can remove and take up large amounts of snow. [12] They are usually warmer than comparable snow-covered areas, sometimes by up to 6 °C (11 °F), which makes them identifiable from brightness temperature imaging. This warming is due to the lower albedo of the blue ice compared to snow, which results in them absorbing more sunlight and warming more. [13] Blue-ice areas also alter the climate above them. [14]

As commonly defined, blue-ice areas display little or no evidence of melting, [1] thus excluding glaciers and frozen lakes in the Antarctic Dry Valleys where sublimation-dominated ice also occurs, but which may be more comparable to the ablation areas of regular glaciers. [4]

Occurrence

Occurrence of blue-ice areas (dark blue) in Antarctica Antarctic blueice hg.jpg
Occurrence of blue-ice areas (dark blue) in Antarctica

Blue-ice areas were first discovered in 1949-1952 by the Norwegian–British–Swedish Antarctic Expedition. [15] They have been identified only in Antarctica, [4] although similar ice patches on Greenland have been reported [4] and blue ice is widespread at glaciers worldwide. [16] Blue-ice areas make up only about 1% of the Antarctic surface ice; [3] however, they are locally common [11] and scattered across the continent, especially in coastal or mountainous areas, [14] but not directly beside the coastline. [17]

They have been found in Dronning Maud Land, the catchment of the Lambert Glacier, the Transantarctic Mountains and Victoria Land. [18] Individual locations in Antarctica include areas of the Allan Hills, [11] the Queen Fabiola Mountains (the Yamato ice field there covers an area of 4,000 square kilometres (1,500 sq mi) and is the largest such structure), [19] Scharffenberg-Botnen [20] and the Sør Rondane Mountains. [4] Their location has been correlated with specific atmospheric pressures, temperatures [21] and a relative humidity of less than 100%. [8]

Origin and processes

Blue-ice areas are regions where more snow is removed by sublimation or by wind than accumulates by precipitation or wind-driven transport, [2] leading to the emergence of (blue) ice. In most of Antarctica, the net tendency is for snow to accumulate except in coastal Antarctica where melting occurs and blue-ice areas where sublimation dominates. [1] This sublimation occurs at rates of 3–350 centimetres per year (1.2–137.8 in/year) snow water equivalent and is balanced by ice flow, with the sublimation rate decreasing with elevation [20] and increasing with temperature. Summer also increases the sublimation rate, although it still occurs during winter. [22] Winds remove snow that rest on the surface and could even scour exposed ice away, although the occurrence of scouring is not established without doubt [23] and the role of abrasion is also unclear. [12]

Such areas exist even in the coldest parts of Antarctica, [2] and they are characterized by high mean wind speeds and low precipitation. [19] Once they have formed, the smooth surface prevents snow from accumulating as it is quickly blown away by the wind, and the blue colour increases the absorption of sunlight and thus sublimation; both these phenomena act to maintain the blue-ice area, and wind-driven transport of warm air can cause the blue-ice area to expand downwind. [24]

Blue-ice areas are common in mountainous regions. Presumably, irregular surface topography obstructs ice flow and locally creates atmospheric conditions suitable for the development of blue-ice areas. Irregular topography does not need to be exposed to the surface to generate blue-ice areas, [11] although they must have an effect on the ice surface topography to induce the formation of blue-ice areas. Consequently, many blue-ice areas form when ice thicknesses decrease, which has been postulated to happen during interglacials [24] although in general the past history of blue-ice areas is poorly known. Such areas may not have existed at all during glacial times when the ice sheet was thicker. [9] Changes in mean wind speeds cause short-term fluctuations in the land covered by blue-ice areas. Global warming is predicted to decrease wind speeds across Antarctica causing a small decrease in the land surface covered by blue-ice areas. [25] Thermal contraction of blue-ice can cause icequakes. [26] There is evidence that microbial ecosystems can form in blue-ice, when there are cryoconites. [27]

Age

Ages of particular blue-ice areas have been inferred from the ages of the meteorites there discovered, although redistribution of meteorites between various areas through ice flow can cause this procedure to yield erroneous age estimates. The oldest blue-ice areas may be up to 2.5 million years old [24] and the ice in them can be quite old as well, with ages of several hundred thousand years estimated on the basis of ice flow dynamics and radiometric dating and the development of a horizontal stratigraphy. This occurs because ice blocked by obstacles stagnates and moves at a rate commensurate with the ablation rate. [20] Younger ages have been found as well however, such as 250,000 years old at the Allan Hills, 75,000 years old at the Yamato Mountains, [9] and 25,000 years old at the Larsen blue-ice area. [28]

Types

Several subtypes have been defined, [11] which encompass most blue-ice areas. [19]

Meteorites

Pathways of meteorites in ice Icemvmt.gif
Pathways of meteorites in ice

Blue-ice areas are known primarily for the meteorites that accumulate there. They originally fell on ice elsewhere and were transported by ice flows to the blue-ice area, where they accumulate [2] when the ice they were encased in ablates away; this mechanism has been compared to a conveyor belt that transports meteorites to blue-ice areas. [29] Additionally, meteorites that fell directly on the blue-ice areas are represented; because of the often great age of the surface a number of meteorites can accumulate even without ice-driven transport. [30] Over 20,000 meteorites from blue-ice areas were known by 1999, a large share of all known meteorites on Earth. [2]

Meteorite findings occur only on a minority of all blue-ice areas [16] and are mostly limited to inland blue-ice areas whereas coastal ones tend to be lacking in meteorites. [3] This might reflect the fact that at low altitude the ice surrounding the meteorites can melt due to solar heating of the meteorite, thus removing it from view. [31] Many meteorites are threatened by climate change, which can cause the meteorites to melt into the underlying ice. [32]

Research history

The earliest research in blue-ice areas occurred during the Norwegian–British–Swedish Antarctic Expedition in 1949–1952, and was followed by two decades of mostly geological and geomorphological research. The discovery of meteorites in a blue-ice area of the Yamato Mountains led to an uptick in scientific interest; a number of programs to collect meteorites began. This also led to increased research in the glaciological [2] and dynamical properties of blue-ice areas, and later to their meteorological and climatological implications. [1]

Use

The hard, flat and smooth surfaces of blue-ice areas have been used as aircraft runways (Blue ice runways) in parts of Antarctica. [14] The very old ice in blue-ice areas has been used to reconstruct past climate, and the temporal resolution may be larger than in deep ice cores. [14] Blue-ice areas are candidate sites for ice core drilling aimed at recovering 1.5 million year old ice, [33] and 2.7 million year old ice has been recovered from such areas. [34]

Related Research Articles

<span class="mw-page-title-main">Glacier</span> Persistent body of ice that moves downhill under its own weight

A glacier is a persistent body of dense ice that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such as crevasses and seracs, as it slowly flows and deforms under stresses induced by its weight. As it moves, it abrades rock and debris from its substrate to create landforms such as cirques, moraines, or fjords. Although a glacier may flow into a body of water, it forms only on land and is distinct from the much thinner sea ice and lake ice that form on the surface of bodies of water.

<span class="mw-page-title-main">Iceberg</span> Large piece of freshwater ice broken off a glacier or ice shelf and floating in open water

An iceberg is a piece of freshwater ice more than 15 meters long that has broken off a glacier or an ice shelf and is floating freely in open water. Smaller chunks of floating glacially derived ice are called "growlers" or "bergy bits". Much of an iceberg is below the water's surface, which led to the expression "tip of the iceberg" to illustrate a small part of a larger unseen issue. Icebergs are considered a serious maritime hazard.

<span class="mw-page-title-main">Climate of Antarctica</span>

The climate of Antarctica is the coldest on Earth. The continent is also extremely dry, averaging 166 mm (6.5 in) of precipitation per year. Snow rarely melts on most parts of the continent, and, after being compressed, becomes the glacier ice that makes up the ice sheet. Weather fronts rarely penetrate far into the continent, because of the katabatic winds. Most of Antarctica has an ice-cap climate with extremely cold and dry weather.

<span class="mw-page-title-main">Weddell Sea</span> Part of the Southern Ocean between Coats Land and the Antarctic Peninsula

The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha Coast, Queen Maud Land. To the east of Cape Norvegia is the King Haakon VII Sea. Much of the southern part of the sea is covered by a permanent, massive ice shelf field, the Filchner-Ronne Ice Shelf.

<span class="mw-page-title-main">Katabatic wind</span> Wind taking high-density air down-slope

A katabatic wind carries high-density air from a higher elevation down a slope under the force of gravity. Such winds are sometimes also called fall winds; the spelling catabatic winds is also used. Katabatic winds can rush down elevated slopes at hurricane speeds, but most are not that intense and many are 10 knots or less.

<span class="mw-page-title-main">Ice shelf</span> Large platform of glacial ice

An ice shelf is a large platform of glacial ice floating on the ocean, fed by one or multiple tributary glaciers. Ice shelves form along coastlines where the ice thickness is insufficient to displace the more dense surrounding ocean water. The boundary between the ice shelf (floating) and grounded ice is referred to as the grounding line; the boundary between the ice shelf and the open ocean is the ice front or calving front.

<span class="mw-page-title-main">Ice core</span> Cylindrical sample drilled from an ice sheet

An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ice formed over a range of years. Cores are drilled with hand augers or powered drills; they can reach depths of over two miles (3.2 km), and contain ice up to 800,000 years old.

<span class="mw-page-title-main">Ice sheet</span> Large mass of glacial tulips

In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than 50,000 km2 (19,000 sq mi). The only current ice sheets are the Antarctic ice sheet and the Greenland ice sheet. Ice sheets are bigger than ice shelves or alpine glaciers. Masses of ice covering less than 50,000 km2 are termed an ice cap. An ice cap will typically feed a series of glaciers around its periphery.

<span class="mw-page-title-main">West Antarctic Ice Sheet</span> Segment of Antarctic ice sheet

The West Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere. It is classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea.

<span class="mw-page-title-main">Micrometeorite</span> Meteoroid that survives Earths atmosphere

A micrometeorite is a micrometeoroid that has survived entry through the Earth's atmosphere. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more abundant, and different in composition. The IAU officially defines meteoroids as 30 micrometers to 1 meter; micrometeorites are the small end of the range (~submillimeter). They are a subset of cosmic dust, which also includes the smaller interplanetary dust particles (IDPs).

<span class="mw-page-title-main">Mount Moulton</span> Mountain in Antarctica

Mount Moulton is a 40-kilometre-long (25 mi) complex of ice-covered shield volcanoes, standing 25 kilometres (16 mi) east of Mount Berlin in the Flood Range, Marie Byrd Land, Antarctica. It is named for Richard S. Moulton, chief dog driver at West Base. The volcano is of Pliocene age and is presently inactive.

<span class="mw-page-title-main">ANSMET</span> Program funded by the National Science Foundation

ANSMET is a program funded by the Office of Polar Programs of the National Science Foundation that looks for meteorites in the Transantarctic Mountains. This geographical area serves as a collection point for meteorites that have originally fallen on the extensive high-altitude ice fields throughout Antarctica. Such meteorites are quickly covered by subsequent snowfall and begin a centuries-long journey traveling "downhill" across the Antarctic continent while embedded in a vast sheet of flowing ice. Portions of such flowing ice can be halted by natural barriers such as the Transantarctic Mountains. Subsequent wind erosion of the motionless ice brings trapped meteorites back to the surface once more where they may be collected. This process concentrates meteorites in a few specific areas to much higher concentrations than they are normally found everywhere else. The contrast of the dark meteorites against the white snow, and lack of terrestrial rocks on the ice, makes such meteorites relatively easy to find. However, the vast majority of such ice-embedded meteorites eventually slide undiscovered into the ocean.

<span class="mw-page-title-main">Blue ice (glacial)</span> Form of ice formed under high pressure in a glacier

Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of the glacier. During compression, air bubbles are squeezed out, so ice crystals enlarge. This enlargement is responsible for the ice's blue colour.

<span class="mw-page-title-main">Ice stream</span> A region of fast-moving ice within an ice sheet

An ice stream is a region of fast-moving ice within an ice sheet. It is a type of glacier, a body of ice that moves under its own weight. They can move upwards of 1,000 metres (3,300 ft) a year, and can be up to 50 kilometres (31 mi) in width, and hundreds of kilometers in length. They tend to be about 2 km (1.2 mi) deep at the thickest, and constitute the majority of the ice that leaves the sheet. In Antarctica, the ice streams account for approximately 90% of the sheet's mass loss per year, and approximately 50% of the mass loss in Greenland.

<span class="mw-page-title-main">Nordenskjöld Coast</span> Coast in Antarctica

The Nordenskjöld Coast is located on the Antarctic Peninsula, more specifically Graham Land, which is the top region of the Peninsula. The Peninsula is a thin, long ice sheet with an Alpine-style mountain chain. The coast consists of 15m tall ice cliffs with ice shelves.

<span class="mw-page-title-main">Totten Glacier</span> Glacier in Antarctica

Totten Glacier is a large glacier draining a major portion of the East Antarctic Ice Sheet, through the Budd Coast of Wilkes Land in the Australian Antarctic Territory. The catchment drained by the glacier is estimated at 538,000 km2 (208,000 sq mi), extending approximately 1,100 km (680 mi) into the interior and holds the potential to raise sea level by at least 3.5 m (11 ft). Totten drains northeastward from the continental ice but turns northwestward at the coast where it terminates in a prominent tongue close east of Cape Waldron. It was first delineated from aerial photographs taken by USN Operation Highjump (1946–47), and named by Advisory Committee on Antarctic Names (US-ACAN) for George M. Totten, midshipman on USS Vincennes of the United States Exploring Expedition (1838–42), who assisted Lieutenant Charles Wilkes with correction of the survey data obtained by the expedition.

<span class="mw-page-title-main">East Antarctic Ice Sheet</span> Segment of the continental ice sheet that covers East Antarctica

The East Antarctic Ice Sheet (EAIS) lies between 45° west and 168° east longitudinally. It was first formed around 34 million years ago, and it is the largest ice sheet on the entire planet, with far greater volume than the Greenland ice sheet or the West Antarctic Ice Sheet (WAIS), from which it is separated by the Transantarctic Mountains. The ice sheet is around 2.2 km (1.4 mi) thick on average and is 4,897 m (16,066 ft) at its thickest point. It is also home to the geographic South Pole, South Magnetic Pole and the Amundsen–Scott South Pole Station.

<span class="mw-page-title-main">Antarctica</span> Earths southernmost continent

Antarctica is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest continent, being about 40% larger than Europe, and has an area of 14,200,000 km2 (5,500,000 sq mi). Most of Antarctica is covered by the Antarctic ice sheet, with an average thickness of 1.9 km (1.2 mi).

<span class="mw-page-title-main">Antarctic sea ice</span> Sea ice of the Southern Ocean

Antarctic sea ice is the sea ice of the Southern Ocean. It extends from the far north in the winter and retreats to almost the coastline every summer. Sea ice is frozen seawater that is usually less than a few meters thick. This is the opposite of ice shelves, which are formed by glaciers; they float in the sea, and are up to a kilometre thick. There are two subdivisions of sea ice: fast ice, which are attached to land; and ice floes, which are not.

<span class="mw-page-title-main">Climate change in Antarctica</span> Impacts of climate change on Antarctica

Climate change caused by greenhouse gas emissions from human activities occurs everywhere on Earth, and while Antarctica is less vulnerable to it than any other continent, climate change in Antarctica has been observed. Since 1959, there has been an average temperature increase of >0.05 °C/decade since 1957 across the continent, although it had been uneven. West Antarctica warmed by over 0.1 °C/decade from the 1950s to the 2000s, and the exposed Antarctic Peninsula has warmed by 3 °C (5.4 °F) since the mid-20th century. The colder, stabler East Antarctica had been experiencing cooling until the 2000s. Around Antarctica, the Southern Ocean has absorbed more oceanic heat than any other ocean, and has seen strong warming at depths below 2,000 m (6,600 ft). Around the West Antarctic, the ocean has warmed by 1 °C (1.8 °F) since 1955.

References

Citations

  1. 1 2 3 4 Bintanja 1999, p. 338.
  2. 1 2 3 4 5 6 Bintanja 1999, p. 337.
  3. 1 2 3 4 Harvey 2003, p. 100.
  4. 1 2 3 4 5 6 Bintanja 1999, p. 340.
  5. ↑ Harvey, Meibom & Haack 2001, p. 809.
  6. 1 2 Bintanja 1999, p. 353.
  7. ↑ Bintanja 1999, p. 352.
  8. 1 2 Bordiec et al. 2020, p. 4.
  9. 1 2 3 Hättestrand & Johansen 2005, p. 228.
  10. ↑ Hättestrand & Johansen 2005, p. 231.
  11. 1 2 3 4 5 6 7 8 9 Bintanja 1999, p. 341.
  12. 1 2 Harvey 2003, p. 103.
  13. ↑ Bintanja 1999, p. 351.
  14. 1 2 3 4 Wang et al. 2014, p. 129.
  15. ↑ Sugden, David; Hall, Adrian (1 December 2020). "Antarctic blue-ice moraines: Analogue for Northern Hemisphere ice sheets?". Quaternary Science Reviews. 249: 2. Bibcode:2020QSRv..24906620S. doi:10.1016/j.quascirev.2020.106620. hdl: 20.500.11820/3c7c71a6-b3f2-4db3-932a-f977e8eae45f . ISSN   0277-3791. S2CID   226344722.
  16. 1 2 Harvey, Meibom & Haack 2001, p. 808.
  17. ↑ Bintanja 1999, p. 356.
  18. ↑ Wang et al. 2014, p. 135.
  19. 1 2 3 4 5 6 7 Bintanja 1999, p. 343.
  20. 1 2 3 Bintanja 1999, p. 345.
  21. ↑ Bordiec et al. 2020, p. 3.
  22. ↑ Bintanja 1999, p. 346.
  23. ↑ Bintanja 1999, p. 347.
  24. 1 2 3 Bintanja 1999, p. 344.
  25. ↑ Bintanja 1999, p. 355.
  26. ↑ Winter, Kate; Lombardi, Denis; Diaz-Moreno, Alejandro; Bainbridge, Rupert (7 April 2021). "Monitoring Icequakes in East Antarctica with the Raspberry Shake". Seismological Research Letters. 92 (5): 2746. doi:10.1785/0220200483. ISSN   0895-0695. S2CID   233568465.
  27. ↑ Nowak, Aga; Isaksson, Elisabeth; Sunde, Øyvind; Elvevold, Synnøve; Sandven, Håkon; Moholdt, Geir; Hudson, Stephen R.; Urset, Anne; Edwards, Arwyn; Rassner, Sara M. E.; Pearce, David; Hamre, Børge; Hodson, Andrew (24 June 2024). "Antarctic Blue Ice Areas are hydrologically active, nutrient rich and contain microbially diverse cryoconite holes". Communications Earth & Environment. 5 (1): 7. doi:10.1038/s43247-024-01487-4.
  28. ↑ Lee, Giyoon; Ahn, Jinho; Ju, Hyeontae; Ritterbusch, Florian; Oyabu, Ikumi; Buizert, Christo; Kim, Songyi; Moon, Jangil; Ghosh, Sambit; Kawamura, Kenji; Lu, Zheng-Tian (15 June 2022). "Chronostratigraphy of the Larsen blue-ice area in northern Victoria Land, East Antarctica, and its implications for paleoclimate". The Cryosphere. 16 (6): 2301–2324. Bibcode:2022TCry...16.2301L. doi: 10.5194/tc-16-2301-2022 . ISSN   1994-0416. S2CID   249736029.
  29. ↑ Harvey 2003, p. 102.
  30. ↑ Harvey 2003, pp. 104–105.
  31. ↑ Harvey 2003, p. 111.
  32. ↑ Tollenaar, Veronica; Zekollari, Harry; Kittel, Christoph; Farinotti, Daniel; Lhermitte, Stef; Debaille, Vinciane; Goderis, Steven; Claeys, Philippe; Joy, Katherine Helen; Pattyn, Frank (April 2024). "Antarctic meteorites threatened by climate warming". Nature Climate Change. 14 (4): 342–343. doi:10.1038/s41558-024-01954-y.
  33. ↑ Kurbatov, A.; Brook, E.; Campbell, S. W.; Conway, H.; Dunbar, N. W.; Higgins, J. A.; Iverson, N. A.; Kehrl, L. M.; McIntosh, W. C.; Spaulding, N. E.; Yan, Y.; Mayewski, P. A. (1 December 2016). "Allan Hills Pleistocene Ice Project (PIP)". AGU Fall Meeting Abstracts. 2016: 31B–2272. Bibcode:2016AGUFMPP31B2272K.
  34. ↑ Voosen, Paul (18 August 2017). "2.7-million-year-old ice opens window on past". Science. 357 (6352): 630–631. Bibcode:2017Sci...357..630V. doi:10.1126/science.357.6352.630. ISSN   0036-8075. PMID   28818920.

Sources

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.