There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land; only that it must be a body of solid phase matter in the polar region. This causes the term "polar ice cap" to be something of a misnomer, as the term ice cap itself is applied more narrowly to bodies that are over land, and cover less than 50,000 km2: larger bodies are referred to as ice sheets.
Earth's polar caps have changed dramatically over the last 12,000 years. Seasonal variations of the ice caps takes place due to varied solar energy absorption as the planet or moon revolves around the Sun. Additionally, in geologic time scales, the ice caps may grow or shrink due to climate variation. If the polar ice caps are too hot then they will melt. However if they are too cold they will increase their sizes.
Earth's North Pole is covered by floating pack ice (sea ice) over the Arctic Ocean. Portions of the ice that do not melt seasonally can get very thick, up to 3–4 meters thick over large areas, with ridges up to 20 meters thick. One-year ice is usually about 1 meter thick. The area covered by sea ice ranges between 9 and 12 million km2. In addition, the Greenland ice sheet covers about 1.71 million km2 and contains about 2.6 million km³ of ice. When the ice breaks off (calves) it forms icebergs scattered around the northern Atlantic.
According to the National Snow and Ice Data Center, "since 1979, winter Arctic ice extent has decreased about 4.2 percent per decade". Both 2008 and 2009 had a minimum Arctic sea ice extent somewhat above that of 2007. At other times of the year the ice extent is still sometimes near the 1979–2000 average, as in April 2010, by the data from the National Snow and Ice Data Center. Still, between these same years, the overall average ice coverage appears to have declined from 8 million km2 to 5 million km2.
Earth's south polar land mass, Antarctica, is covered by the Antarctic ice sheet. It covers an area of about 14.6 million km2 and contains between 25 and 30 million km3 of ice. Around 70% of the fresh water on Earth is contained in this ice sheet.
Data from the National Snow and Ice Data Center shows that the sea ice coverage of Antarctica has a slightly positive trend over the last three decades (1979–2009).
Over the past several decades, Earth's polar ice caps have gained significant attention because of the alarming decrease in land and sea ice. NASA reports that since the late 1970s, the Arctic has lost an average of 20,800 square miles (53,900 square kilometers) of ice per year while the Antarctic has gained an average of 7,300 square miles (18,900 km2) of ice per year. On 19 September 2014, for the first time since 1979, Antarctic sea ice extent exceeded 7.72 million square miles (20 million square kilometers), according to the National Snow and Ice Data Center. The ice extent stayed above this benchmark extent for several days. The average maximum extent between 1981 and 2010 was 7.23 million square miles (18.72 million square kilometers). The single-day maximum extent in 2014 was reached on 20 Sep, according to NSIDC data, when the sea ice covered 7.78 million square miles (20.14 million square kilometers). The 2014 five-day average maximum was reached on 22 Sep, when sea ice covered 7.76 million square miles (20.11 million square kilometers), according to NSIDC.
The current rate of decline of the ice caps has caused many investigations and discoveries on glacier dynamics and their influence on the world's climate. In the early 1950s, scientists and engineers from the US Army began drilling into polar ice caps for geological insight. These studies resulted in “nearly forty years of research experience and achievements in deep polar ice core drillings... and established the fundamental drilling technology for retrieving deep ice cores for climatologic archives.”  Polar ice caps have been used to track current climate patterns but also patterns over the past several thousands years from the traces of CO2 and CH4 found trapped in the ice. In the past decade, polar ice caps have shown their most rapid decline in size with no true sign of recovery. Josefino Comiso, a senior research scientist at NASA, found that the “rate of warming in the Arctic over the last 20 years is eight times the rate of warming over the last 100 years.” In September 2012, sea ice reached its smallest size ever. Journalist John Vidal stated that sea ice is "700,000 sq km below the previous minimum of 4.17m sq km set in 2007". In August 2013, Arctic sea ice extent averaged 6.09m km2, which represents 1.13 million km2 below the 1981–2010 average for that month.
In addition to Earth, the planet Mars also has polar ice caps. They consist of primarily water-ice with a few percent dust. Frozen carbon dioxide makes up a small permanent portion of the Planum Australe or the South Polar Layered Deposits. In both hemispheres a seasonal carbon dioxide frost deposits in the winter and sublimes during the spring.
Data collected in 2001 from NASA missions to Mars show that the southern residual ice cap undergoes sublimation inter-annually. The most widely accepted explanation is that fluctuations in the planet's orbit are causing the changes.
On 29 April 2015, NASA stated that its New Horizons missions had discovered a feature thought to be a polar ice cap on the dwarf planet Pluto. The probe's flyby of Pluto in July 2015 allowed the Alice ultraviolet imaging spectrometer to confirm that the feature was in fact an ice cap composed of methane and nitrogen ices.
Abalos Undae (Latin for "Abalos Waves") is a dune field on Mars in the periphery of Planum Boreum, the Martian North pole. It is one of the officially named northern circumpolar dune fields, along with Olympia, Hyperboreae, and Siton Undae, and also one of the densest of the region. Its northernmost boundary is located in the southwest channel that separates the Abalos Colles formation from the main polar ice cap, and from there the dune field extends southwest all the way to the lowlands of Vastitas Borealis.It is theorised that the dunes of the Abalos field may have resulted from erosion of Rupes Tenuis (Latin: Thin Cliff), the polar scarp. Its name was approved by the International Astronomical Union in 1988. It extends from latitude 74.94°N to 82.2°N and from longitude 261.4°E to 283.03°E (76.97°W – 98.6°W). Its origin is located at classical albedo feature with coordinates 72°N, 70°W and has a diameter of 442.74 km.Chasma Boreale
Chasma Boreale is a large canyon in Mars's north polar ice cap in the Mare Boreum quadrangle of Mars at 83° north latitude and 47.1° west longitude. It is about 560 km (350 mi) long and was named after a classical albedo feature name. The canyon's sides reveal layered features within the ice cap that result from seasonal melting and deposition of ice, together with dust deposits from Martian dust storms. Information about the past climate of Mars may eventually be revealed in these layers, just as tree ring patterns and ice core data do on Earth. Both polar caps also display grooved features, probably caused by wind flow patterns. The grooves are also influenced by the amount of dust. The more dust, the darker the surface. The darker the surface, the more melting as dark surfaces absorb more energy.Hubert Wilkins
Sir George Hubert Wilkins MC & Bar (31 October 1888 – 30 November 1958) was an Australian polar explorer, ornithologist, pilot, soldier, geographer and photographer. He was awarded the Military Cross, when he assumed command of a group of American soldiers who had lost their officers during the Battle of the Hindenburg Line, and became the only official Australian photographer from any war to receive a combat medal. He narrowly failed in an attempt to be the first to cross under the North Pole in a submarine, but was able to prove that submarines were capable of operating beneath the polar ice cap, thereby paving the way for future successful missions. The US Navy later took his ashes to the North Pole aboard the submarine USS Skate on 17 March 1959.Korolev (Martian crater)
Korolev is an ice-filled impact crater in the Mare Boreum quadrangle of Mars, located at 73° north latitude and 165° east longitude. It is 81.4 kilometres (50.6 mi) in diameter and contains about 2,200 cubic kilometres (530 cu mi) of water ice, comparable in volume to Great Bear Lake in northern Canada. The crater was named after Sergei Korolev (1907–1966), the head Soviet rocket engineer and designer during the Space Race in the 1950s and 1960s.Korolev crater is located on the Planum Boreum, the northern polar plain which surrounds the north polar ice cap, near the Olympia Undae dune field. The crater rim rises about 2 kilometres (1.2 mi) above the surrounding plains. The crater floor lies about 2 kilometres (1.2 mi) below the rim, and is covered by a 1.8 kilometres (1.1 mi) deep central mound of permanent water ice, up to 60 kilometres (37 mi) in diameter.Mare Australe quadrangle
The Mare Australe quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Mare Australe quadrangle is also referred to as MC-30 (Mars Chart-30). The quadrangle covers all the area of Mars south of 65°, including the South polar ice cap, and its surrounding area. The quadrangle's name derives from an older name for a feature that is now called Planum Australe, a large plain surrounding the polar cap. The Mars polar lander crash landed in this region.Mare Boreum quadrangle
The Mare Boreum quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Mare Boreum quadrangle is also referred to as MC-1 (Mars Chart-1). Its name derives from an older name for a feature that is now called Planum Boreum, a large plain surrounding the polar cap.The quadrangle covers all of the Martian surface north of latitude 65°. It includes the north polar ice cap, which has a swirl pattern and is roughly 1,100 km across. Mariner 9 in 1972 discovered a belt of sand dunes that ring the polar ice deposits, which is 500 km across in some places and may be the largest dune field in the solar system. The ice cap is surrounded by the vast plains of Planum Boreum and Vastitas Borealis. Close to the pole, there is a large valley, Chasma Boreale, that may have been formed from water melting from the ice cap. An alternative view is that it was made by winds coming off the cold pole. Another prominent feature is a smooth rise, formerly called Olympia Planitia. In the summer, a dark collar around the residual cap becomes visible; it is mostly caused by dunes. The quadrangle includes some very large craters that stand out in the north because the area is smooth with little change in topography. These large craters are Lomonosov and Korolev. Although smaller, the crater Stokes is also prominent.
The Phoenix lander landed on Vastitas Borealis within the Mare Boreum quadrangle at 68.218830° N and 234.250778° E on May 25, 2008.
The probe collected and analyzed soil samples in an effort to detect water and determine how hospitable the planet might once have been for life to grow. It remained active there until winter conditions became too harsh around five months later.After the mission ended the journal Science reported that chloride, bicarbonate, magnesium, sodium potassium, calcium, and possibly sulfate were detected in the samples analyzed by Phoenix. The pH was narrowed down to 7.7±0.5. Perchlorate (ClO4), a strong oxidizer at elevated temperatures, was detected. This was a significant discovery because the chemical has the potential of being used for rocket fuel and as a source of oxygen for future colonists. Also, under certain conditions perchlorate can inhibit life; however some microorganisms obtain energy from the substance (by anaerobic reduction). The chemical when mixed with water can greatly lower freezing points, in a manner similar to how salt is applied to roads to melt ice. So, perchlorate may be allowing small amounts of liquid water to form on Mars today. Gullies, which are common in certain areas of Mars, may have formed from perchlorate melting ice and causing water to erode soil on steep slopes.Much direct evidence was found for water at this location.Martian polar ice caps
The planet Mars has two permanent polar ice caps. During a pole's winter, it lies in continuous darkness, chilling the surface and causing the deposition of 25–30% of the atmosphere into slabs of CO2 ice (dry ice). When the poles are again exposed to sunlight, the frozen CO2 sublimes. These seasonal actions transport large amounts of dust and water vapor, giving rise to Earth-like frost and large cirrus clouds.
The caps at both poles consist primarily of water ice. Frozen carbon dioxide accumulates as a comparatively thin layer about one metre thick on the north cap in the northern winter, while the south cap has a permanent dry ice cover about 8 m thick. The northern polar cap has a diameter of about 1000 km during the northern Mars summer, and contains about 1.6 million cubic km of ice, which if spread evenly on the cap would be 2 km thick. (This compares to a volume of 2.85 million cubic km (km3) for the Greenland ice sheet.) The southern polar cap has a diameter of 350 km and a thickness of 3 km. The total volume of ice in the south polar cap plus the adjacent layered deposits has also been estimated at 1.6 million cubic km. Both polar caps show spiral troughs, which recent analysis of SHARAD ice penetrating radar has shown are a result of roughly perpendicular katabatic winds that spiral due to the Coriolis Effect.The seasonal frosting of some areas near the southern ice cap results in the formation of transparent 1 m thick slabs of dry ice above the ground. With the arrival of spring, sunlight warms the subsurface and pressure from subliming CO2 builds up under a slab, elevating and ultimately rupturing it. This leads to geyser-like eruptions of CO2 gas mixed with dark basaltic sand or dust. This process is rapid, observed happening in the space of a few days, weeks or months, a rate of change rather unusual in geology—especially for Mars. The gas rushing underneath a slab to the site of a geyser carves a spider-like pattern of radial channels under the ice.In July 2018, Italian scientists reported the discovery of a subglacial lake on Mars, 1.5 km (0.93 mi) below the surface of the southern polar layered deposits (not under the visible permanent ice cap), and about 20 km (12 mi) across, the first known stable body of water on the planet.Norge (airship)
The Norge was a semi-rigid Italian-built airship that carried out the first verified trip of any kind to the North Pole and likely the first verified overflight on 12 May 1926. It was also the first aircraft to fly over the polar ice cap between Europe and America. The expedition was the brainchild of polar explorer and expedition leader Roald Amundsen, the airship's designer and pilot Umberto Nobile and American explorer Lincoln Ellsworth, who along with the Aero Club of Norway, financed the trip which was known as the Amundsen-Ellsworth 1926 Transpolar Flight.Planum Australe
Planum Australe (Latin: "the southern plain") is the southern polar plain on Mars. It extends southward of roughly 75°S and is centered at 83.9°S 160.0°E / -83.9; 160.0. The geology of this region was to be explored by the failed NASA mission Mars Polar Lander, which lost contact on entry into the Martian atmosphere.
In July 2018, scientists reported the discovery, based on MARSIS radar studies, of a subglacial lake on Mars, 1.5 km (0.93 mi) below the southern polar ice cap, and extending sideways about 20 km (12 mi), the first known stable body of water on the planet.Planum Boreum
Planum Boreum (Latin: "the northern plain") is the northern polar plain on Mars. It extends northward from roughly 80°N and is centered at 88.0°N 15.0°E / 88.0; 15.0. Surrounding the high polar plain is a flat and featureless lowland plain called Vastitas Borealis which extends for approximately 1500 kilometres southwards, dominating the northern hemisphere.Polar route
A polar route is an aircraft route across the uninhabited polar ice cap regions. The term "polar route" was originally applied to great circle routes between Europe and the west coast of North America in the 1950s.Project Boreas
Project Boreas was a study conducted between 2003 and 2006 by the British Interplanetary Society to design a station on the Planum Boreum at the Martian North Pole. The project was international, involving over 25 scientists and engineers, co-ordinated by Charles S. Cockell. Pole Station was designed to operate for three summers and two polar winters. Amongst a diversity of scientific objectives the station occupants were to retrieve a deep core from within the Martian polar ice cap and search for water and habitable conditions deep in the polar ice cap. Expeditions were planned to numerous locations across the Martian north polar cap, including the Chasma Boreale and the polar layered terrains. The study involved wide-ranging investigations of the scientific priorities for a human presence at the Martian polar ice caps through to detailed architectural and design studies for the station. Studies were undertaken on mobility and communications and psycho-social issues for long-term operation at the Martian polar station.Siton Undae
Siton Undae is one of the largest and densest dune fields in the vicinity of Planum Boreum, the Martian northern polar ice-cap. It is named after one of the classical albedo features on Mars. Its name was officially approved by IAU on 20 March 2007. It extends from latitude 73.79°N to 77.5°N and from longitude 291.38°E to 301.4°E (43.98°W – 57.08°W). Its centre is located at latitude 75.55°N, longitude 297.28E (62.72°W), and has a diameter of 222.97 kilometres (138.55 mi).Siton Undae is part of a cluster of sand-seas (undae), which along with Hyperboreae, and Abalos Undae, overlay the lowlands of Vastitas Borealis. Siton Undae superposes the deepest basin of the northern region of Mars and contains amorphous silica-coated glass-rich dunes. It is theorised that the formation of Siton Undae may have occurred during early erosion incidents of the Planum Boreum cavi unit, and that Rupes Tenuis may also have been a sand source, although it is now depleted. Other dune fields sharing the same formation history include Olympia and Aspledon Undae.Siton Undae is the southernmost of the densest northern circumpolar dune fields and its presence indicates effective sand transport and accumulation from sand sources to the north and west. Siton Undae, along with Abalos, and Hyperboreae Undae, is also a tributary to less dense dune fields that continue all the way to the Martian prime meridian.Sno-Freighter
The Sno-Freighter is a one-of-a-kind land vehicle designed by LeTourneau Technologies (now part of Cameron International) for Alaska Freight Lines in the 1950s. During that decade, Alaska Freight Lines won the contract to transport construction material to build the Distant Early Warning Line (DEW) in far northern Alaska and Canada. At the time, no roads crossed the Arctic Circle in North America, there were almost no runways for air transportation, and the polar ice cap prevented seaborne transport.
LeTourneau had built a series of prototype "land trains" for use in roadless environments, and Alaska Freight Lines contracted the company to build a special model for cold-climate transportation on January 5, 1955. The contract called for an off-road vehicle capable of transporting 150 short tons (140,000 kg) of cargo in −68 °F (−56 °C) temperatures, through 4-foot (1.2 m) deep streams, and deep snowdrifts.Using parts from its previous land trains, LeTourneau manufactured the Model VC-22 Sno-Freighter, completing it on February 17. It left the factory in Longview, Texas on March 16. The "locomotive" (serial # 5198) of the Sno-Freighter contained two Cummins NHV-12BI V-12 diesel engines operating at 400 horsepower each. These engines drove 24 electric motors (one for each wheel on the locomotive and trailing cars). Each car (serials # 5199-5203) measured 40-foot (12 m) in length and was 16-foot (4.9 m) wide. They carried 30 tons each for a combined payload of 150 tons for the 274-foot (84 m) long Sno-Freighter. Its first trip under power was in the Fall of 1955, when Alaska Freight Lines began their 400-mile trek north from Fairbanks, Alaska to the Arctic Ocean. During its second trip north in the Fall of 1956, the Sno-Freighter jack-knifed and its engines burned just north of Eagle, Alaska. The cargo was off-loaded onto either "Cat" trains (Caterpillar bulldozers pulling cargo sleds) or one of the eleven 1956 Mack LRVSW semi trucks that Alaska Freight Lines had purchased to supplement the Sno-Freighter.
Today, the Sno-Freighter is abandoned and lies next to the Steese Highway in Fox, Alaska.Swiss cheese features
Swiss cheese features (SCFs) are curious pits in the south polar ice cap of Mars (Mare Australe quadrangle) named from their similarity to the holes in Swiss cheese. They were first seen in 2000 using Mars Orbiter Camera imagery. They are typically a few hundred meters across and 8 metres deep, with a flat base and steep sides. They tend to have similar bean-like shapes with a cusp pointing towards the south pole, indicating that insolation is involved in their formation. The angle of the Sun probably contributes to their roundness. Near the Martian summer solstice, the Sun can remain continuously just above the horizon; as a result the walls of a round depression will receive more intense sunlight, and sublimate much more rapidly than the floor. The walls sublimate and recede, while the floor remains the same.
As the seasonal frost disappears, the pit walls appear to darken considerably relative to the surrounding terrain. The SCFs have been observed to grow in size, year by year, at an average rate of 1 to 3 meters, suggesting that they are formed in a thin layer (8m) of carbon dioxide ice lying on top of water ice. Later research with HiRISE showed that the pits are in a 1-10 meter thick layer of dry ice that is sitting on a much larger water ice cap. Pits have been observed to begin with small areas along faint fractures. The circular pits have steep walls that work to focus sunlight, thereby increasing erosion. For a pit to develop, a steep wall of about 10 cm and a length of over 5 meters is necessary.Sympagic ecology
A sympagic environment is one where water exists mostly as a solid, ice, such as a polar ice cap or glacier. Solid sea ice is permeated with channels filled with salty brine. These briny channels and the sea ice itself have its ecology, referred to as "sympagic ecology".
Residents of temperate or tropical climates often assume, mistakenly, that ice and snow are devoid of life. In fact, a number of varieties of algae such as diatoms engage in photosynthesis in arctic and alpine regions of Earth. Other energy sources include Aeolian dust and pollen swept in from other regions. These ecosystems also include bacteria and fungi, as well as animals like flatworms and crustaceans. A number of sympagic worm species are commonly called ice worms.
Additionally, the ocean has abundant plankton, and prolific algal blooms occur in the polar regions each summer as well as in high mountain lakes, bringing nutrients to those parts of the ice in contact with the water.
In the spring, krill can scrape off the green lawn of ice algae from the underside of the pack ice.The Blue Marble
The Blue Marble is an image of Earth taken on December 7, 1972, from a distance of about 29,000 kilometers (18,000 miles) from the planet's surface. It was taken by the crew of the Apollo 17 spacecraft on its way to the Moon, and is one of the most reproduced images in history.The image has the official NASA designation AS17-148-22727 and mainly shows the Earth from the Mediterranean Sea to Antarctica. This was the first time the Apollo trajectory made it possible to photograph the south polar ice cap, despite the Southern Hemisphere being heavily covered in clouds. In addition to the Arabian Peninsula and Madagascar, almost the entire coastline of Africa is clearly visible. The Asian mainland is on the horizon.
NASA has also applied the name to a 2012 series of images which cover the entire globe at relatively high resolution. These were created by looking through satellite-pictures taken over time in order to find as many cloudless photographs as possible to use in the final images.Waterworld
Waterworld is a 1995 American post-apocalyptic science fiction action film directed by Kevin Reynolds and co-written by Peter Rader and David Twohy. It was based on Rader's original 1986 screenplay and stars Kevin Costner, who also produced it with Charles Gordon and John Davis. It was distributed by Universal Pictures.
The setting of the film is in the distant future. Although no exact date was given in the film itself, it has been suggested that it takes place in 2500. The polar ice cap has completely melted, and the sea level has risen over 7,600 m (25,000 feet), covering nearly all of the land. The plot of the film centers on an otherwise nameless antihero, "The Mariner", a drifter who sails the Earth in his trimaran.
The most expensive film ever made at the time, Waterworld was released to mixed reviews, praising the futuristic setting and premise but criticizing the characterization and acting performances. The film also was unable to recoup its massive budget at the box office; however, the film did later become profitable due to video and other post-cinema sales. The film was also nominated for an Academy Award in the category Best Sound at the 68th Academy Awards.
The film's release was accompanied by a novelization, video game, and three themed attractions at Universal Studios Hollywood, Universal Studios Singapore, and Universal Studios Japan called Waterworld: A Live Sea War Spectacular, all of which are still running as of 2019.