Research stations in Antarctica
A number of governments have set up permanent research stations in Antarctica and these bases are distributed. Unlike the drifting ice stations set up in the Arctic, the research stations of the Antarctic are constructed either on rock or on ice, fixed in place. Many of the stations are staffed around the year. A total of 42 countries, all signatories to the Antarctic Treaty, operate seasonal and year-round research stations on the continent; the population of people performing and supporting scientific research on the continent and nearby islands varies from 4,000 during the summer season to 1,000 during winter. In addition to these permanent stations 30 field camps are established each summer to support specific projects. During the Heroic Age of Antarctic Exploration in the late 19th century, the first bases on the continent were established. In 1898, Carsten Borchgrevink, a Norwegian/British explorer, led the British Antarctic Expedition to Cape Adare, where he established the first Antarctic base on Ridley Beach.
The expedition is referred to now as the'Southern Cross' Expedition, after their ship's name. Most of the staff were Norwegian, but the funds for the expedition were British, provided by Sir George Newnes; the 10 members of the expedition explored Robinson Bay to the west of Cape Adare by dog teams, after being picked up by the ship at the base, went ashore on the Ross Ice Shelf for brief journeys. The expedition hut is still in good condition and visited by tourists; the hut was occupied by Scott's Northern Party under the command of Victor Campbell for a year in 1911, after its attempt to explore the eastern end of the ice shelf discovered Roald Amundsen ashore preparing for his assault on the South Pole. In 1903, Dr William S. Bruce's Scottish National Antarctic Expedition set off to Antarctica, with one of its aims to establish a meteorological station in the area. After the expedition failed to find land, Bruce decided to head back to the Laurie Island in the South Orkneys and find an anchorage there.
The islands were well-situated as a site for a meteorological station, their relative proximity to the South American mainland allowed a permanent station to be established. Bruce instituted a comprehensive programme of work, involving meteorological readings, trawling for marine samples, botanical excursions, the collection of biological and geological specimens; the major task completed during this time was the construction of a stone building, christened "Omond House". This was to act as living accommodation for the parties that would remain on Laurie Island to operate the proposed meteorological laboratory; the building was constructed from local materials using the dry stone method, with a roof improvised from wood and canvas sheeting. The completed house was 20 feet by 20 feet square, with two windows, fitted as quarters for six people. Rudmose Brown wrote: "Considering that we had no mortar and no masons' tools it is a wonderfully fine house and lasting. I should think it will be standing a century hence..."Bruce offered to Argentina the transfer of the station and instruments on the condition that the government committed itself to the continuation of the scientific mission.
Bruce informed the British officer William Haggard of his intentions in December 1903, Haggard ratified the terms of Bruce proposition. The Scotia sailed back for Laurie Island on 14 January 1904 carrying on board Argentinean officials from the Ministry of Agriculture, National Meteorological Office, Ministry of Livestock and National Postal and Telegraphs Office. In 1906, Argentina communicated to the international community the establishment of a permanent base on South Orkney Islands. Little happened for the following forty years until the Second World War, when the British launched Operation Tabarin in 1943, to establish a presence on the continent; the chief reason was to establish solid British claims to various uninhabited islands and parts of Antarctica, reinforced by Argentine sympathies toward Germany. Prior to the start of the war, German aircraft had dropped markers with swastikas across Queen Maud Land in an attempt to create a territorial claim, see New Swabia. Led by Lieutenant James Marr, the 14-strong team left the Falkland Islands in two ships, HMS William Scoresby and Fitzroy, on Saturday January 29, 1944.
Marr had accompanied the British explorer Sir Ernest Shackleton on his final Antarctic expedition in 1921 - 1922. Bases were established during February near the abandoned Norwegian whaling station on Deception Island, where the Union Flag was hoisted in place of Argentine flags, at Port Lockroy on the coast of Graham Land. A further base was founded at Hope Bay on February 13, 1945, after a failed attempt to unload stores on February 7, 1944; these bases were the first to be constructed on the mainland Antarctica. The Operation provoked a massive expansion in international activity after the war. Chile organized its First Chilean Antarctic Expedition in 1947–48. Among other accomplishments, it brought the Chilean president Gabriel González Videla to inaugurate one of its bases, thereby becoming the first head of state to set foot on the continent. Signy Research Station was established in 1947, Australia's Mawson Station in 1954, Dumont d'Urville Station was the first French station in 1956.
In that same year, the United States built McMurdo Station and Amundsen–Scott South Pole Station, the Soviet Union built Mirny Station. The United States maintains the southernmost Base and the largest base and research station in Antarctica, Amundsen–Scott South Pole Station; the second-southernmost base is the Chinese Kunlun Statio
A solstice is an event occurring when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21; the seasons of the year are determined by reference to the equinoxes. The term solstice can be used in a broader sense, as the day when this occurs; the day of a solstice in either hemisphere has either the most sunlight of the year or the least sunlight of the year for any place other than the Equator. Alternative terms, with no ambiguity as to which hemisphere is the context, are "June solstice" and "December solstice", referring to the months in which they take place every year; the word solstice is derived from the Latin sol and sistere, because at the solstices, the Sun's declination appears to "stand still". For an observer on the North Pole, the Sun reaches the highest position in the sky once a year in June; the day this occurs is called the June solstice day. For an observer on the South Pole, the Sun reaches the highest position on the December solstice day.
When it is the summer solstice at one Pole, it is the winter solstice on the other. The Sun's westerly motion never ceases. However, the Sun's motion in declination comes to a stop at the moment of solstice. In that sense, solstice means "sun-standing"; this modern scientific word descends from a Latin scientific word in use in the late Roman Republic of the 1st century BC: solstitium. Pliny uses it a number of times in his Natural History with a similar meaning, it contains two Latin-language morphemes, sol, "sun", -stitium, "stoppage". The Romans used "standing" to refer to a component of the relative velocity of the Sun as it is observed in the sky. Relative velocity is the motion of an object from the point of view of an observer in a frame of reference. From a fixed position on the ground, the Sun appears to orbit around Earth. To an observer in an inertial frame of reference, planet Earth is seen to rotate about an axis and revolve around the Sun in an elliptical path with the Sun at one focus.
Earth's axis is tilted with respect to the plane of Earth's orbit and this axis maintains a position that changes little with respect to the background of stars. An observer on Earth therefore sees a solar path, the result of both rotation and revolution; the component of the Sun's motion seen by an earthbound observer caused by the revolution of the tilted axis – which, keeping the same angle in space, is oriented toward or away from the Sun – is an observed daily increment of the elevation of the Sun at noon for six months and observed daily decrement for the remaining six months. At maximum or minimum elevation, the relative yearly motion of the Sun perpendicular to the horizon stops and reverses direction. Outside of the tropics, the maximum elevation occurs at the summer solstice and the minimum at the winter solstice; the path of the Sun, or ecliptic, sweeps north and south between the northern and southern hemispheres. The days are shorter around the winter solstice; when the Sun's path crosses the equator, the length of the nights at latitudes +L° and -L° are of equal length.
This is known as an equinox. There are two equinoxes in a tropical year; the seasons occur because the Earth's axis of rotation is not perpendicular to its orbital plane but makes an angle of about 23.44°, because the axis keeps its orientation with respect to an inertial frame of reference. As a consequence, for half the year the Northern Hemisphere is inclined toward the Sun while for the other half year the Southern Hemisphere has this distinction; the two moments when the inclination of Earth's rotational axis has maximum effect are the solstices. At the June solstice the subsolar point is further north than any other time: at latitude 23.44° north, known as the Tropic of Cancer. At the December solstice the subsolar point is further south than any other time: at latitude 23.44° south, known as the Tropic of Capricorn. The subsolar point will cross every latitude between these two extremes twice per year. During the June solstice, places on the Arctic Circle will see the Sun just on the horizon during midnight, all places north of it will see the Sun above horizon for 24 hours.
That is the midnight midsummer-night sun or polar day. On the other hand, places on the Antarctic Circle will see the Sun just on the horizon during midday, all places south of it will not see the Sun above horizon at any time of the day; that is the polar night. During the December Solstice, the effects on both hemispheres are just the opposite; this allows the polar sea ice to increase its annual growth and temporary extent at a greater level due to lack of direct sunlight. The concept of the solstices was embedded in ancient Greek celestial navigation; as soon as they discovered that the Earth is spherical they devised the concept of the celestial sphere, an imaginary spherical surface rotating with the heavenly bodies fixed in it. As long as no assumptions are made concerning the distances of those bodies from Earth or from each other, the sphere can be accepted as real and is in fact still in use; the Ancient Greeks use meaning stand of the Sun. The stars move across the inner surf
The polar night occurs in the northernmost and southernmost regions of the Earth when the night lasts for more than 24 hours. This occurs only inside the polar circles; the opposite phenomenon, the polar day, or midnight sun, occurs when the Sun stays above the horizon for more than 24 hours. "Night" is understood as the center of the Sun being below a free horizon. Since the atmosphere bends the rays of the Sun, the polar day is longer than the polar night, the area, affected by polar night is somewhat smaller than the area of midnight sun; the polar circle is located at a latitude between these two areas, at the latitude of 66.5 degrees. In the northernmost city of Sweden, Kiruna, at 67°51'N, the polar night lasts for around 28 twenty-four-hour periods, while the midnight sun lasts around 50 twenty-four-hour periods. While it is day in the Arctic Circle, it is night in the Antarctic Circle, vice versa. Any planet or moon with a sufficient axial tilt that rotates with respect to its star more than it orbits the star will experience the same phenomenon.
The polar shortest day is not dark everywhere inside the polar circle, but only in places within about 5.5° of the poles, only when the moon is well below the horizon. Regions located at the inner border of the polar circles experience polar twilight instead of polar night. In fact, polar regions get more twilight throughout the year than equatorial regions. For regions inside the polar circles, the maximum lengths of the time that the Sun is below the horizon varies from zero a few degrees beyond the Arctic Circle and Antarctic Circle to 179 days at the Poles. However, not all this time is classified as polar night since sunlight may be visible because of refraction; the time when any part of the Sun is above the horizon at the poles is 186 days. The preceding numbers are average numbers: the ellipticity of the Earth's orbit makes the South Pole receive a week more of Sun-below-horizon than the North Pole; as there are various kinds of twilight, there exist various kinds of polar night. Each kind of polar night is defined as.
The descriptions below are based on clear skies, so the sky will be darker in the presence of dense clouds. Polar twilight occurs in areas that are located at the inner border of the polar circles, where the Sun will be on or below the horizon all day on the winter solstice. There is no true daylight at the solar culmination, only civil twilight; this means that the Sun is below the horizon, but by less than 6°. During civil twilight, there may still be enough light for most normal outdoor activities because of light scattering by the upper atmosphere and refraction. Street lamps may remain on and a person looking at a window from within a brightly lit room may see their reflection at noon, as the level of outdoor illuminance will be below that of many illuminated indoor spaces. Sufferers of seasonal affective disorder tend to seek out therapy with artificial light, as the psychological benefits of daylight require high levels of ambient light which are not present in any stage of twilight; the civil polar night period produces only a faint glow of light visible at midday.
It happens when there is no civil twilight and only nautical twilight occurs at the solar culmination. Civil twilight happens when the Sun is between 0 and 6° below the horizon, civil night when it is lower than that. Therefore, the civil polar night is limited to latitudes above 72° 34', 6° inside the polar circle. Nowhere on mainland Europe is this definition met. On the Norwegian territory of Svalbard, civil polar night lasts from about 11 November until 30 January. Dikson, in Russia, experiences civil polar night for a month. During dense cloud cover places like the coast of Finnmark in Norway will get a darker "day". On the Canadian territory of Pond Inlet, Nunavut however civil polar night lasts from about 16 December until 26 December. During the nautical polar night period, there is no trace of daylight, except around midday, it happens when there is no nautical twilight and only astronomical twilight occurs at the solar culmination. Nautical twilight happens when the Sun is between twelve degrees below the horizon.
There is a location at the horizon around midday with more light than others because of refraction. During nautical night, the Sun is lower than 12° below the horizon, so nautical polar night is limited to latitudes above 78° 34', 12° within the polar circle, or 11.5° from the pole. Alert, the northernmost settlement in Canada and the world, experiences this from November 19 to January 22; the northernmost point of land, at the end of Greenland at Oodap Qeqertaa, experiences this from November 15 to January 27. On the Canadian territory of Eureka, Nunavut in Canada experiences this December 2 to January 8. On the Norwegian territory of Svalbard Ny-Alesund experiences this from December 13 to December 31; the astronomical polar night is a period of continuous night. Astronomical twilight happens when the Sun is between twelve and eighteen degrees below the horizon and astronomical night when it is lower than that. Thus, the astronomical polar night is limited to latitudes above 84° 34', 18° within the polar circle, or five and a half degrees from the pole.
During the astronomical polar night stars of the sixth magnitude, which are the dimmest stars visible to the naked eye, wil
An iceberg is a large piece of freshwater ice that has broken off a glacier or an ice shelf and is floating in open water. Another name for iceberg is "ice mountain". Small bits of disintegrating icebergs are called "growlers" or "bergy bits". Icebergs are possible on Earth because the oceans are filled with liquid water, a substance less dense when solid than liquid. Planets with oceans consisting of different substances like methane cannot have icebergs, as their chunks of frozen liquid would sink; because 90 percent of an iceberg is below the surface and not visible, icebergs have been considered a serious maritime hazard since the 1912 loss of the "unsinkable" RMS Titanic, leading to the formation of the International Ice Patrol in 1914. The expression "tip of the iceberg", illustrates a difficulty, only a small, visible part of a larger, complex problem; the largest iceberg reliably recorded was Iceberg B-15A which split off the Ross Ice Shelf in Antarctica in 2000. The word iceberg is a partial loan translation from the Dutch word ijsberg meaning ice mountain, cognate to Danish isbjerg, German Eisberg, Low Saxon Iesbarg and Swedish isberg.
Because the density of pure ice is about 920 kg/m3, that of seawater about 1025 kg/m3 about one-tenth of the volume of an iceberg is above water. The shape of the underwater portion can be difficult to judge by looking at the portion above the surface; the visible "tips" of icebergs range from 1 to 75 metres above sea level and weigh 100,000 to 200,000 metric tons. The largest known iceberg in the North Atlantic was 168 metres above sea level, reported by the USCG icebreaker East Wind in 1958, making it the height of a 55-story building; these icebergs originate from the glaciers of western Greenland and may have interior temperatures of −15 to −20 °C. Winds and currents tend to move icebergs close to coastlines, where they can become frozen into pack ice, or drift into shallow waters, where they can come into contact with the seabed, a phenomenon called seabed gouging; the largest icebergs recorded have been calved, or broken off, from the Ross Ice Shelf of Antarctica. Iceberg B-15, photographed by satellite in 2000, measured 295 by 37 kilometres, with a surface area of 11,000 square kilometres.
The largest iceberg on record was an Antarctic tabular iceberg of over 31,000 square kilometres sighted 150 miles west of Scott Island, in the South Pacific Ocean, by the USS Glacier on November 12, 1956. This iceberg was larger than Belgium. A small iceberg less than 2 meters across that floats with less than 1 meter showing above water is called a growler, is smaller than a bergy bit, less than 5 meters in size. Both are spawned from disintegrating icebergs; as a piece of iceberg ice melts, it produces a fizzing sound called the "Bergie Seltzer". This sound results; as this happens, each bubble bursts. The bubbles contain air trapped in snow layers early in the history of the ice, that got buried to a given depth and pressurized as it transformed into firn to glacial ice. In addition to size classification, icebergs can be classified on the basis of their shape; the two basic types of iceberg forms are non-tabular. Tabular icebergs have steep sides and a flat top, much like a plateau, with a length-to-height ratio of more than 5:1.
This type of iceberg known as an ice island, can be quite large, as in the case of Pobeda Ice Island. Antarctic icebergs formed by breaking off from an ice shelf, such as the Ross Ice Shelf or Filchner-Ronne Ice Shelf, are tabular; the largest icebergs in the world are formed this way. Non-tabular icebergs include: Dome: An iceberg with a rounded top. Pinnacle: An iceberg with one or more spires. Wedge: An iceberg with a steep edge on one side and a slope on the opposite side. Dry-Dock: An iceberg that has eroded to form a slot or channel. Blocky: An iceberg with steep, vertical sides and a flat top, it differs from tabular icebergs in that its aspect ratio, the ratio between its width and height, is small, more like that of a block than a flat sheet. Before the early 1910s, although there had been many fatal sinkings of ships by icebergs, there was no system in place to track icebergs to guard ships against collisions. In 1907, SS Kronprinz Wilhelm, a German liner, had rammed an iceberg and suffered a crushed bow, but was still able to complete her voyage.
The advent of steel ship construction led designers to declare their ships "unsinkable". The April 1912 sinking of the Titanic, which killed 1,518 of its 2,223 passengers and crew, changed all that. For the remainder of the ice season of that year, the United States Navy patrolled the waters and monitored ice flow. In November 1913, the International Conference on the Safety of Life at Sea met in London to devise a more permanent system of observing icebergs. Within three months the participating maritime nations had formed the International Ice Patrol; the goal of the IIP was to collect data on meteorology and oceanography to measure currents, ice-flow, ocean temperature, salinity levels. They monitored iceberg dangers near the Grand Banks of Newfoundland and provided the "limits of all known ice" in that vicinity to the maritime community; the IIP published their first records in 1921, which allowed for a year-by-year comparison of iceberg movement. Aerial surveillance of the seas in the early
The tidal force is an apparent force that stretches a body towards and away from the center of mass of another body due to a gradient in gravitational field from the other body. It arises because the gravitational field exerted on one body by another is not constant across its parts: the nearest side is attracted more than the farthest side, it is this difference. Thus, the tidal force is known as the differential force, as well as a secondary effect of the gravitational field. In celestial mechanics, the expression tidal force can refer to a situation in which a body or material is under the gravitational influence of a second body, but is perturbed by the gravitational effects of a third body; the perturbing force is sometimes in such cases called a tidal force: it is the difference between the force exerted by the third body on the second and the force exerted by the third body on the first. When a body is acted on by the gravity of another body, the field can vary on body 1 between the side of the body facing body 2 and the side facing away from body 2.
Figure 4 shows the differential force of gravity on a spherical body exerted by another body. These so-called tidal forces cause strains on both bodies and may distort them or in extreme cases, break one or the other apart; the Roche limit is the distance from a planet at which tidal effects would cause an object to disintegrate because the differential force of gravity from the planet overcomes the attraction of the parts of the object for one another. These strains would not occur if the gravitational field were uniform, because a uniform field only causes the entire body to accelerate together in the same direction and at the same rate; the relationship of an astronomical body's size, to its distance from another body influences the magnitude of tidal force. The tidal force acting on an astronomical body, such as the Earth, is directly proportional to the diameter of that astronomical body and inversely proportional to the cube of the distance from another body producing a gravitational attraction, such as the Moon or the Sun.
Tidal action on bath tubs, swimming pools and other small bodies of water is negligible. Figure 3 is a graph showing. In this graph, the attractive force decreases in proportion to the square of the distance, while the slope relative to value decreases in direct proportion to the distance; this is why the gradient or tidal force at any point is inversely proportional to the cube of the distance. The tidal force corresponds to the difference in Y between two points on the graph, with one point on the near side of the body, the other point on the far side; the tidal force becomes larger, when the two points are either farther apart, or when they are more to the left on the graph, meaning closer to the attracting body. For example, the Moon produces a greater tidal force on the Earth than the Sun though the Sun exerts a greater gravitational attraction on the Earth than the Moon, because the gradient is less; the Moon produces a greater tidal force on the Earth, than the tidal force of the Earth on the Moon.
The distance is the same, but the diameter of the Earth is greater than the diameter of the Moon, resulting in a greater tidal force. What matters is not the total gravitational attraction on a body, but the difference from one side to the other; the greater the diameter of the body, the more difference there will be from one side to the other. Gravitational attraction is inversely proportional to the square of the distance from the source; the attraction will be stronger on the side of a body facing the source, weaker on the side away from the source. The tidal force is proportional to the difference; as expected, the table below shows that the distance from the Moon to the Earth, is the same as the distance from the Earth to the Moon. The Earth is 81 times more massive than the Moon but has 4 times its radius; as a result, at the same distance, the tidal force per unit mass of the Earth on the Moon is about 20 times stronger than that of the Moon on the Earth. Thus the Earth was able to lock the Moon's rotation to its orbit around the Earth but not vice versa.
In the case of an infinitesimally small elastic sphere, the effect of a tidal force is to distort the shape of the body without any change in volume. The sphere becomes an ellipsoid with two bulges, pointing away from the other body. Larger objects distort into an ovoid, are compressed, what happens to the Earth's oceans under the action of the Moon; the Earth and Moon rotate about their common center of mass or barycenter, their gravitational attraction provides the centripetal force necessary to maintain this motion. To an observer on the Earth close to this barycenter, the situation is one of the Earth as body 1 acted upon by the gravity of the Moon as body 2. All parts of the Earth are subject to the Moon's gravitational forces, causing the water in the oceans to redistribute, forming bulges on the sides near the Moon and far from the Moon; when a body rotates while subject to tidal forces, internal friction results in the gradual dissipation of its rotational kinetic energy as heat. In the case for the Earth, Earth's Moon, the loss of rotational kinetic energy results in a gain of about 2 milliseconds per century.
If the body is close
Wilkes Land is a large district of land in eastern Antarctica, formally claimed by Australia as part of the Australian Antarctic Territory, though the validity of this claim has been placed for the period of the operation of the Antarctic Treaty, to which Australia is a signatory. It fronts on the southern Indian Ocean between Queen Mary Coast and Adelie Land, extending from Cape Hordern in 100°31' E to Pourquoi Pas Point, in 136°11' E; the region extends as a sector about 2600 km towards the South Pole, with an estimated land area of 2,600,000 km² glaciated. It is further subdivided in the following coastal areas which can be thought of as sectors extending to the South Pole: Knox Land: 100°31' E to 109°16' E Budd Land: 109°16' E to 115°33' E Sabrina Land: 115°33' E to 122°05' E Banzare Land: 122°05' E to 130°10' E Clarie Land: 130°10' E to 136°11' EIn a wider sense, Wilkes Land extends further East to Point Alden in 142°02' E, thereby including Adélie Land, claimed by France. Wilkes Land is named after Lieutenant Charles Wilkes, the American explorer who commanded the 1838–42 United States Exploring Expedition.
The naming is in recognition of Wilkes' discovery of the continental margin over a distance of 2,400 km of coast, thus providing substantial proof that Antarctica is a continent. This definition of extent excludes the area east of 142°02' E, George V Land, sighted by Wilkes but has been shown by expeditions to be further south than the positions assigned by him. In 2006 a team of researchers led by Ralph von Frese and Laramie Potts used gravity measurements by NASA's GRACE satellites to discover the 300-mile-wide Wilkes Land crater, which formed about 250 million years ago. Wilkes Land is featured prominently in the 1998 film The X-Files. Fox Mulder journeys to Antarctica to save his partner Dana Scully, being held there against her will. In the process, they discover a huge secret lab under the surface run by the Cigarette-Smoking Man. Adélie Valley