1.
Seawater
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Seawater, or salt water, is water from a sea or ocean. On average, seawater in the oceans has a salinity of about 3. 5% This means that every kilogram of seawater has approximately 35 grams of dissolved salts. Average density at the surface is 1.025 kg/l, seawater is denser than both fresh water and pure water because the dissolved salts increase the mass by a larger proportion than the volume. The freezing point of seawater decreases as salt concentration increases, at typical salinity, it freezes at about −2 °C. The coldest seawater ever recorded was in 2010, in a stream under an Antarctic glacier, seawater pH is typically limited to a range between 7.5 and 8.4. However, there is no universally accepted reference pH-scale for seawater, although the vast majority of seawater has a salinity of between 31 g/kg and 38 g/kg, seawater is not uniformly saline throughout the world. Where mixing occurs with fresh water runoff from river mouths, near melting glaciers or vast amounts precipitation, the most saline open sea is the Red Sea, where high rates of evaporation, low precipitation and low river run-off, and confined circulation result in unusually salty water. The salinity in isolated bodies of water can be considerably greater still, historically, several salinity scales were used to approximate the absolute salinity of seawater. A popular scale was the Practical Salinity Scale where salinity was measured in practical salinity units, the current standard for salinity is the Reference Salinity scale with the salinity expressed in units of g/kg. The density of surface seawater ranges from about 1020 to 1029 kg/m3, depending on the temperature, at a temperature of 25 °C, salinity of 35 g/kg and 1 atm pressure, the density of seawater is 1023.6 kg/m3. Deep in the ocean, under pressure, seawater can reach a density of 1050 kg/m3 or higher. The density of seawater also changes with salinity, brines generated by seawater desalination plants can have salinities up to 120 g/kg. The density of typical seawater brine of 120 g/kg salinity at 25 °C, seawater pH is limited to the range 7.5 to 8.4. The speed of sound in seawater is about 1,500 m/s, and varies with temperature, salinity. The thermal conductivity of seawater is 0.6 W/mK at 25 °C, the thermal conductivity decreases with increasing salinity and increases with increasing temperature. Seawater contains more dissolved ions than all types of freshwater, however, the ratios of solutes differ dramatically. Bicarbonate ions also constitute 48% of river water solutes but only 0. 14% of all seawater ions, differences like these are due to the varying residence times of seawater solutes, sodium and chlorine have very long residence times, while calcium tends to precipitate much more quickly. The most abundant dissolved ions in seawater are sodium, chloride, magnesium, sulfate and its osmolarity is about 1000 mOsm/l
2.
Ice
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Ice is water frozen into a solid state. Depending on the presence of such as particles of soil or bubbles of air. In the Solar System, ice is abundant and occurs naturally from as close to the Sun as Mercury to as far as away the Oort cloud objects, beyond the Solar System, it occurs as interstellar ice. It falls as snowflakes and hail or occurs as frost, icicles or ice spikes, Ice molecules can exhibit up to sixteen different phases that depend on temperature and pressure. When water is cooled rapidly, up to three different types of ice can form depending on the history of its pressure and temperature. When cooled slowly correlated proton tunneling occurs below 20 K giving rise to macroscopic quantum phenomena, virtually all the ice on Earths surface and in its atmosphere is of a hexagonal crystalline structure denoted as ice Ih with minute traces of cubic ice denoted as ice Ic. The most common phase transition to ice Ih occurs when water is cooled below 0°C at standard atmospheric pressure. It may also be deposited directly by water vapor, as happens in the formation of frost, the transition from ice to water is melting and from ice directly to water vapor is sublimation. Ice is used in a variety of ways, including cooling, winter sports, as a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered a mineral. It possesses a regular crystalline structure based on the molecule of water, an unusual property of ice frozen at atmospheric pressure is that the solid is approximately 8. 3% less dense than liquid water. The density of ice is 0.9167 g/cm3 at 0 °C, liquid water is densest, essentially 1.00 g/cm³, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid, density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm³ at −180 °C. When water freezes, it increases in volume and it is also a common cause of the flooding of houses when water pipes burst due to the pressure of expanding water when it freezes. The result of this process is that ice floats on liquid water, sufficiently thin ice sheets allow light to pass through while protecting the underside from short-term weather extremes such as wind chill. This creates an environment for bacterial and algal colonies. When ice melts, it absorbs as much energy as it would take to heat an equivalent mass of water by 80 °C, during the melting process, the temperature remains constant at 0 °C. While melting, any energy added breaks the bonds between ice molecules. Energy becomes available to increase the thermal energy only after enough hydrogen bonds are broken that the ice can be considered liquid water, the amount of energy consumed in breaking hydrogen bonds in the transition from ice to water is known as the heat of fusion
3.
Density
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The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume. As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
4.
Fresh water
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Fresh water is generally characterized by having low concentrations of dissolved salts and other total dissolved solids. The term specifically excludes seawater and brackish water although it does include mineral-rich waters such as chalybeate springs, the term sweet water has been used to describe fresh water in contrast to salt water. The term fresh water does not have the meaning as potable water. Much of the fresh water and ground water is unsuitable for drinking without some form of purification because of the presence of chemical or biological contaminants. It may also be in contact with the underlying underground water. The majority of water on Earth is in ice caps. The source of almost all water is precipitation from the atmosphere, in the form of mist, rain. Fresh water falling as mist, rain or snow contains materials dissolved from the atmosphere and material from the sea, in some cases this acid rain results in pollution of lakes and rivers. In coastal areas fresh water may contain significant concentrations of salts derived from the sea if windy conditions have lifted drops of seawater into the rain-bearing clouds. This can give rise to elevated concentrations of sodium, chloride, magnesium, significant quantities of iron may be transported in this way including the well-documented transfer of iron-rich rainfall falling in Brazil derived from sand-storms in the Sahara in north Africa. Water is an issue for the survival of all living organisms. Some can use water but many organisms including the great majority of higher plants. Out of all the water on Earth, saline water in oceans, seas and saline groundwater make up about 97% of it. Freshwater lakes contain about 87% of this surface water, including 29% in the African Great Lakes, 20% in Lake Baikal in Russia, 21% in the North American Great Lakes. Swamps have most of the balance only a small amount in rivers. In areas with no water on the ground surface, fresh water derived from precipitation may, because of its lower density. Most of the fresh water is frozen in ice sheets. Many areas suffer from lack of distribution of water, such as deserts
5.
Polar regions of Earth
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The polar regions of Earth, also known as Earths frigid zones, are the regions of Earth surrounding its geographical poles. These regions are dominated by Earths polar ice caps, the northern resting on the Arctic Ocean and the southern on the continent of Antarctica. The Arctic has various definitions, including the north of the Arctic Circle, or the region north of 60° north latitude. The Antarctic is usually defined as south of 60° south latitude, the 1959 Antarctic Treaty uses the former definition. The axial tilt of the Earth has an effect on climate of the polar regions. Since the polar regions are the farthest from the equator, they receive the least amount of sunlight and are therefore frigid, the large amount of ice and snow also reflects a large part of what little sunlight the Polar regions receive, contributing to the cold. There are many settlements in Earths north polar region, countries with claims to Arctic regions are, the United States, Canada, Denmark, Norway, Finland, Sweden, Iceland, and Russia. Arctic circumpolar populations often share more in common with other than with other populations within their national boundaries. As such, the polar region is diverse in human settlements. The southern polar region has no permanent human habitation, mcMurdo Station is the largest research station in Antarctica, run by the United States. Other notable stations include Palmer Station and Amundsen–Scott South Pole Station, Esperanza Base and Marambio Base, Scott Base, while there are no indigenous human cultures, there is a complex ecosystem, especially along Antarcticas coastal zones. Coastal upwelling provides abundant nutrients which feeds krill, a type of marine crustacea, other planets and natural satellites in the solar system have interesting quirks about their polar regions. Earths Moon is thought to contain deposits of ice in deep craters in its polar regions. Mars, like Earth, has ice caps. Meanwhile, on Uranus, the tilt of the planets axis leads to the poles alternately pointing almost directly at the Sun. Man and the Conquest of the Poles, trans. by Scott Sullivan, new York, Simon & Schuster,1963
6.
Arctic ice pack
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The Arctic ice pack is the ice cover of the Arctic Ocean and its vicinity. The Arctic ice pack undergoes a seasonal cycle in which ice melts in spring and summer, reaches a minimum around mid-September, then increases during fall. Summer ice cover in the Arctic is about 50% of winter cover, some of the ice survives from one year to the next. Currently 28% of Arctic basin sea ice is ice, thicker than seasonal ice, up to 3–4 meters thick over large areas. As well as the seasonal cycle there has been an underlying trend of declining sea ice in the Arctic in recent decades. Sea ice has an important effect on the balance of the polar oceans, since it insulates the warm ocean from the much colder air above. Sea ice is highly reflective of solar radiation, reflecting about 60% of incoming solar radiation when bare and this is much greater than the reflectivity of the sea and thus the ice also affects the absorption of sunlight at the surface. The sea ice cycle is also an important source of dense bottom water, while freezing, water rejects its salt content, leaving pure ice. The remaining surface water, made dense by the salinity, sinks. This production of water is a factor in maintaining the thermohaline circulation. In the Arctic, a key area where pancake ice forms the dominant ice type over a region is the so-called Odden ice tongue in the Greenland Sea. Most of the old ice continues south, driven by the wind, so an open water surface is exposed on which new ice forms as frazil. Reliable measurements of sea ice edge begin within the satellite era, from the late 1970s, the Scanning Multichannel Microwave Radiometer on Seasat and Nimbus 7 satellites provided information that was independent of solar illumination or meteorological conditions. The frequency and accuracy of passive microwave measurements improved with the launch of the DMSP F8 Special Sensor Microwave/Imager SSMI in 1987. Both the sea ice area and extent are estimated, with the latter being larger, the trends from 1979 to 2002 have been a statistically significant Arctic sea ice decrease of −2. 5% ±0. 9% per decade during those 23 years. Climate models simulated this trend in 2002, the September minimum ice extent trend for 1979–2011 declined by 12. 0% per decade during 32 years. In 2007 the minimum extent fell by more than a million square kilometers, new research shows the Arctic Sea ice to be melting faster than predicted by any of the 18 computer models used by the Intergovernmental Panel on Climate Change in preparing its 2007 assessments. In 2012, a new low of about 3,500,000 km2 was reached
7.
Arctic Ocean
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The Arctic Ocean is the smallest and shallowest of the worlds five major oceans. Alternatively, the Arctic Ocean can be seen as the northernmost part of the all-encompassing World Ocean, located mostly in the Arctic north polar region in the middle of the Northern Hemisphere, the Arctic Ocean is almost completely surrounded by Eurasia and North America. It is partly covered by sea ice throughout the year and almost completely in winter, the summer shrinking of the ice has been quoted at 50%. The US National Snow and Ice Data Center uses satellite data to provide a record of Arctic sea ice cover. The Arctic may become ice free for the first time in human history within a few years or by 2040, for much of European history, the north polar regions remained largely unexplored and their geography conjectural. He was probably describing loose sea ice known today as growlers or bergy bits, his Thule was probably Norway, early cartographers were unsure whether to draw the region around the North Pole as land or water. The makers of navigational charts, more conservative than some of the more fanciful cartographers, tended to leave the region blank and this lack of knowledge of what lay north of the shifting barrier of ice gave rise to a number of conjectures. In England and other European nations, the myth of an Open Polar Sea was persistent, john Barrow, longtime Second Secretary of the British Admiralty, promoted exploration of the region from 1818 to 1845 in search of this. In the United States in the 1850s and 1860s, the explorers Elisha Kane, even quite late in the century, the eminent authority Matthew Fontaine Maury included a description of the Open Polar Sea in his textbook The Physical Geography of the Sea. Nevertheless, as all the explorers who travelled closer and closer to the reported, the polar ice cap is quite thick. Fridtjof Nansen was the first to make a crossing of the Arctic Ocean. The first surface crossing of the ocean was led by Wally Herbert in 1969, in a dog sled expedition from Alaska to Svalbard, with air support. The first nautical transit of the pole was made in 1958 by the submarine USS Nautilus. Since 1937, Soviet and Russian manned drifting ice stations have extensively monitored the Arctic Ocean, scientific settlements were established on the drift ice and carried thousands of kilometres by ice floes. In World War II, the European region of the Arctic Ocean was heavily contested, the Arctic Ocean occupies a roughly circular basin and covers an area of about 14,056,000 km2, almost the size of Antarctica. The coastline is 45,390 km long and it is surrounded by the land masses of Eurasia, North America, Greenland, and by several islands. It is connected to the Pacific Ocean by the Bering Strait and to the Atlantic Ocean through the Greenland Sea, countries bordering the Arctic Ocean are, Russia, Norway, Iceland, Greenland, Canada and the United States. There are several ports and harbours around the Arctic Ocean In Alaska, in Canada, ships may anchor at Churchill in Manitoba, Nanisivik in Nunavut, Tuktoyaktuk or Inuvik in the Northwest territories
8.
Antarctic sea ice
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Antarctic sea ice is the sea ice of the Southern Ocean. It extends far north in winter and retreats almost to the coastline each summer, sea ice freezes from seawater, and is usually less than a few meters thick. It should not be confused with the ice shelves, which are formed by glaciers flowing out into the sea, there are two subdivisions of sea ice, fast ice, which is attached to land, and ice floes, which are not. Sea ice in the Southern Ocean is often snow-covered, and generally melts from below, unlike Arctic ice, on average, Antarctic sea ice is younger, thinner, warmer, saltier, and more mobile than Arctic sea ice. Due to its inaccessibility, it is not as well-studied as Arctic ice, the Antarctic sea ice cover is highly seasonal, with very little ice in the austral summer, expanding to an area roughly equal to that of Antarctica in winter. It peaks during September, which marks the end of austral winter, consequently, most Antarctic sea ice is first year ice, a few meters thick, but the exact thickness is not known. The mass of 18 million km^2 of ice, for each meter of thickness, is 18,000 km^3 and roughly 16 gigatonnes. Since the ocean off the Antarctic coast is almost always warmer than the air over it. If it is pushed quickly, the ice can travel further north before it melts. Most ice is formed along the coast, as the ice leaves areas of open water. Because Antarctic ice is mainly first-year ice, which is not as thick as multiyear ice, snowfall and flooding of the ice can thicken it substantially, and the layer structure of Antarctic ice is often quite complex. Recent changes in wind patterns around Antarctica have advected the sea ice farther north in some areas, the net change is a slight increase in the area of sea ice in the Antarctic seas. Increased sea ice extent does not indicate that the Southern Ocean is cooling, the effect probably has more than one cause. The IPCC fifth Assessment report concluded that Measurements of Antarctic sea ice thickness are too few to be able to judge whether its total volume is decreasing, steady, temperatures in the atmosphere and Southern Ocean have increased during the period 1979–2004. However, sea ice grows faster than it melts, because of a weakly stratified Ocean, thus, this mechanism is responsible for an increase in the net ice production, contributing to more sea ice. The sea ice volume increase presents about half the size of the freshwater supply from the Antarctic ice sheets. Modelling suggests that observed ice-drift toward the regions are responsible for dynamical thickening during autumn. The force of moving ice is considerable, it can crush ships that are caught in the ice pack, icebreakers, iceports and ice piers are used to land supplies
9.
Southern Ocean
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As such, it is regarded as the fourth-largest of the five principal oceanic divisions, smaller than the Pacific, Atlantic, and Indian Oceans but larger than the Arctic Ocean. This ocean zone is cold, northward flowing waters from the Antarctic mix with warmer subantarctic waters. By way of his voyages in the 1770s, Captain James Cook proved that waters encompassed the southern latitudes of the globe. Since then, geographers have disagreed on the Southern Oceans northern boundary or even existence, considering the part of the Pacific, Atlantic. Others regard the seasonally-fluctuating Antarctic Convergence as the natural boundary, Borders and names for oceans and seas were internationally agreed when the International Hydrographic Bureau, the precusor to the IHO, convened the First International Conference on 24 July 1919. The IHO then published these in its Limits of Oceans and Seas, Australian authorities regard the Southern Ocean as lying immediately south of Australia. Map publishers using the term Southern Ocean on their maps include Hema Maps, Southern Ocean is an obsolete name for the Pacific Ocean or South Pacific, coined by Vasco Núñez de Balboa, the first European to discover it, who approached it from the north. The South Seas is an archaic synonym. A1745 British Act of Parliament established a prize for discovering a Northwest Passage to the Western and Southern Ocean of America, authors using Southern Ocean to name the waters encircling the unknown southern polar regions used varying limits. James Cooks account of his second voyage implies New Caledonia borders it, peacocks 1795 Geographical Dictionary said it lay to the southward of America and Africa, John Payne in 1796 used 40 degrees as the northern limit, the 1827 Edinburgh Gazetteer used 50 degrees. The United Kingdoms South Australia Act 1834 described the waters forming the southern limit of the new colony of South Australia as the Southern Ocean. The Colony of Victorias Legislative Council Act of 1881 delimited part of the division of Bairnsdale as along the New South Wales boundary to the Southern ocean. The limit then followed the west coast of Tasmania southwards to the South East Cape and then went eastwards to Broughton Island, New Zealand, the northern limits of the Southern Ocean were moved southwards in the IHOs 1937 second edition of the Limits of Oceans and Seas. From this edition, much of the northern limit ceased to abut land masses. As is discussed in detail below, prior to the 2002 edition the limits of oceans explicitly excluded the seas lying within each of them. The Great Australian Bight was unnamed in the 1928 edition, and it therefore encompassed former Southern Ocean waters but was technically not inside any of the three adjacent oceans by 1937. To perform direct comparisons of current and former limits of oceans it is necessary to consider, or at least be aware of, the limits of the Atlantic, Pacific and Indian Oceans have therefore been extended South to the Antarctic Continent. The IHO readdressed the question of the Southern Ocean in a survey in 2000, of its 68 member nations,28 responded, and all responding members except Argentina agreed to redefine the ocean, reflecting the importance placed by oceanographers on ocean currents
10.
Arctic ecology
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Arctic ecology is the scientific study of the relationships between biotic and abiotic factors in the arctic, the region north of the Arctic Circle. This is a characterized by stressful conditions as a result of extreme cold, low precipitation. The Arctic consists of taiga and tundra biomes, which also dominate very high elevations, sensitive ecosystems exist throughout the Arctic region, which are being impacted dramatically by global warming. The earliest inhabitants of the Arctic were the Neanderthals, since then, many indigenous populations have inhabited the region, which continues to this day. Since the early 1900s, when Vilhjalmur Stefansson led the first major Canadian Arctic Expedition, in 1946, The Arctic Research Laboratory was established in Point Barrow, Alaska under the contract of the Office of Naval Research. This launched an interest in exploring the Arctic examining animal cycles, permafrost, from an anthropological point of view, researchers study the native Inuit peoples of Alaska as they have become extremely accustomed to adapting to ecological and climate variability. To understand Arctic ecology, it is important to both the terrestrial and oceanic aspects of the region. A few important parts of this environment are sea ice and permafrost, sea ice is frozen seawater that moves with oceanic currents, it provides important habitat and a resting place for animals, particularly during the winter months. Over time, small pockets of salty seawater get trapped in the ice, and this causes the ice to become progressively less salty. Sea ice persists throughout the year, but there is less ice available during summer months, large portions of the land are also frozen during the year. Permafrost is substrate that has been frozen for a minimum of 2 years, there are two types of permafrost, discontinuous and continuous. Discontinuous permafrost is found in areas where the annual air temperature is only slightly below freezing. In areas where the mean annual surface temperature is below −5 °C. This is not limited to sheltered areas and ranges from a few inches below the surface to over 300 m deep, the top layer is called the active layer. It thaws in the summer and is critical to plant life, moisture and temperature are major physical drivers of natural ecosystems. The more arid and colder conditions found at higher northern latitudes support tundra, the water in this region is generally frozen and evaporation rates are very low. Tundra is found from 55 ° to 80° N latitude in North America, Eurasia and it can be found at lower latitudes at high elevations as well. The average temperature is −34 °C, during the summer it is less than 10 °C, average precipitation ranges from 10 to 50 cm, and the permafrost is 400–600 m thick
11.
Iceberg
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An iceberg or ice mountain is a large piece of freshwater ice that has broken off a glacier or an ice shelf and is floating freely in open water. It may subsequently become frozen into pack ice, as it drifts into shallower waters, it may come into contact with the seabed, a process referred to as seabed gouging by ice. Almost 91% of an iceberg is below the surface of the water, the word iceberg is a partial loan translation from Dutch ijsberg, literally meaning ice mountain, cognate to Danish isbjerg, German Eisberg, Low Saxon Iesbarg and Swedish isberg. Because the density of ice is about 920 kg/m³. The shape of the underwater portion can be difficult to judge by looking at the portion above the surface and this has led to the expression tip of the iceberg, for a problem or difficulty that is only a small manifestation of a larger problem. Icebergs generally range from 1 to 75 metres above sea level, 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 a temperature of −15 to −20 °C. Icebergs are usually confined by winds and currents to move close to the coast, 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 and this iceberg was larger than Belgium. When a piece of ice melts, it makes a fizzing sound called Bergie Seltzer. This sound is made when the water-ice interface reaches compressed air trapped in the ice. As this happens, each bubble bursts, making a popping sound, the bubbles contain air trapped in snow layers very early in the history of the ice, that eventually got buried to a given depth and pressurized as it transformed into firn then to glacial ice. About a month later, this split into two pieces upon crashing into Joe Island in the Nares Strait next to Greenland. In June 2011, large fragments of the Petermann Ice Islands were observed off the Labrador coast, iceberg B-17B140 km2,1999, shipping alert issued December 2009. In addition to classification, icebergs can be classified on the basis of their shape. The two basic types of forms are tabular and non-tabular. Tabular icebergs have steep sides and a top, much like a plateau. This type of iceberg, also known as an ice island, can be quite large, Antarctic icebergs formed by breaking off from an ice shelf, such as the Ross Ice Shelf or Filchner-Ronne Ice Shelf, are typically tabular
12.
Ice shelf
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An ice shelf is a thick floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland, Canada, the boundary between the floating ice shelf and the grounded ice that feeds it is called the grounding line. The thickness of ice shelves ranges from about 100 to 1000 meters, in contrast, sea ice is formed on water, is much thinner, and forms throughout the Arctic Ocean. It also is found in the Southern Ocean around the continent of Antarctica, Ice shelves are principally driven by gravity-driven pressure from the grounded ice. That flow continually moves ice from the line to the seaward front of the shelf. The primary mechanism of mass loss from ice shelves was thought to have been iceberg calving, typically, a shelf front will extend forward for years or decades between major calving events. Snow accumulation on the surface and melting from the lower surface are also important to the mass balance of an ice shelf. Ice may also accrete onto the underside of the shelf, the density contrast between glacial ice, which is denser than normal ice, and liquid water means that only about 1/9 of the floating ice is above the ocean surface. The worlds largest ice shelves are the Ross Ice Shelf and the Filchner-Ronne Ice Shelf in Antarctica, the term captured ice shelf has been used for the ice over a subglacial lake, such as Lake Vostok. All Canadian ice shelves are attached to Ellesmere Island and lie north of 82°N, Ice shelves that are still in existence are the Alfred Ernest Ice Shelf, Milne Ice Shelf, Ward Hunt Ice Shelf and Smith Ice Shelf. The MClintock Ice Shelf broke up from 1963 to 1966, the Ayles Ice Shelf broke up in 2005, a total of 74 percent of the Antarctic coastline has ice shelves attached. Their aggregate area is over 1,550,000 km2, in the last several decades, glaciologists have observed consistent decreases in ice shelf extent through melt, calving, and complete disintegration of some shelves. The Ellesmere ice shelf reduced by 90 percent in the century, leaving the separate Alfred Ernest, Ayles, Milne, Ward Hunt. A1986 survey of Canadian ice shelves found that 48 km². of ice calved from the Milne, the Ayles Ice Shelf calved entirely on August 13,2005. The Ward Hunt Ice Shelf, the largest remaining section of thick landfast sea ice along the coastline of Ellesmere Island. It further decreased by 27% in thickness between 1967 and 1999, in summer 2002, the Ward Ice Shelf experienced another major breakup. Two sections of Antarcticas Larsen Ice Shelf broke apart into hundreds of small fragments in 1995 and 2002. The breakup events may be linked to the dramatic polar warming trends that are part of global warming, the leading ideas involve enhanced ice fracturing due to surface meltwater and enhanced bottom melting due to warmer ocean water circulating under the floating ice
13.
Glacier
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A glacier is a persistent body of dense ice that is constantly moving under its own weight, it forms where the accumulation of snow exceeds its ablation over many years, often centuries. Glaciers slowly deform and flow due to stresses induced by their weight, creating crevasses, seracs and they also abrade rock and debris from their substrate to create landforms such as cirques and moraines. Glaciers form only on land and are distinct from the much thinner sea ice, between 35°N and 35°S, glaciers occur only in the Himalayas, Andes, Rocky Mountains, a few high mountains in East Africa, Mexico, New Guinea and on Zard Kuh in Iran. Glaciers cover about 10 percent of Earths land surface, continental glaciers cover nearly 13,000,000 km2 or about 98 percent of Antarcticas 13,200,000 km2, with an average thickness of 2,100 m. Greenland and Patagonia also have huge expanses of continental glaciers, Glacial ice is the largest reservoir of fresh water on Earth. Within high altitude and Antarctic environments, the temperature difference is often not sufficient to release meltwater. A large piece of compressed ice, or a glacier, appears blue as large quantities of water appear blue and this is because water molecules absorb other colors more efficiently than blue. The other reason for the color of glaciers is the lack of air bubbles. Air bubbles, which give a color to ice, are squeezed out by pressure increasing the density of the created ice. The word Glaceon is a loanword from French and goes back, via Franco-Provençal, to the Vulgar Latin glaciārium, derived from the Late Latin glacia, the processes and features caused by or related to glaciers are referred to as glacial. The process of establishment, growth and flow is called glaciation. The corresponding area of study is called glaciology, Glaciers are important components of the global cryosphere. Glaciers are categorized by their morphology, thermal characteristics, and behavior, cirque glaciers form on the crests and slopes of mountains. A glacier that fills a valley is called a valley glacier, a large body of glacial ice astride a mountain, mountain range, or volcano is termed an ice cap or ice field. Ice caps have a less than 50,000 km2 by definition. Glacial bodies larger than 50,000 km2 are called ice sheets or continental glaciers, several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces, the only extant ice sheets are the two that cover most of Antarctica and Greenland. They contain vast quantities of water, enough that if both melted, global sea levels would rise by over 70 m
14.
Ice calving
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Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier. It is a form of ice ablation or ice disruption and is caused by the glacier expanding. It is the release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf. The ice that breaks away can be classified as an iceberg, calving of glaciers is often accompanied by a loud cracking or booming sound before blocks of ice up to 60 metres high break loose and crash into the water. The entry of the ice into the water causes large, the waves formed in locations like Johns Hopkins Glacier can be so large that boats cannot approach closer than 3 kilometres. These events have become major tourist attractions in such as Alaska. Many glaciers terminate at oceans or freshwater lakes which results naturally with the calving of large numbers of icebergs, calving of Greenlands glaciers produce 12,000 to 15,000 icebergs each year alone. Calving of ice shelves is usually preceded by a rift and these events are not often observed. Etymologically, calving is cognatic with calving as in bearing a calf and it is useful to classify causes of calving into first, second, and third order processes. First order processes are responsible for the rate of calving at the glacier scale. The first order cause of calving is longitudinal stretching, which controls the formation of crevasses, when crevasses penetrate the full thickness of the ice, calving will occur. Longitudinal stretching is controlled by friction at the base and edges of the glacier, glacier geometry and these factors, therefore, exert the primary control on calving rate. Second and third order calving processes can be considered to be superimposed on the first order process above, melting at the waterline is an important second order calving process as it undercuts the subaerial ice, leading to collapse. Other second order processes include tidal and seismic events, buoyant forces, when calving occurs due to waterline melting, only the subaerial part of the glacier will calve, leaving a submerged foot. Thus, a third order process is defined, whereby upward buoyant forces cause this ice foot to break off and this process is extremely dangerous, as it has been known to occur, without warning, up to 300m from the glacier terminus. Though many factors contribute to calving have been identified, a reliable predictive mathematical formula is still under development. Data is currently being assembled from ice shelves in Antarctica and Greenland to help establish a calving law, there are currently several concepts upon which to base a predictive law. Another theory, based on research, shows that the calving rate increases as a power of the spreading rate near the calving front
15.
Shoal
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Often it refers to those submerged ridges, banks, or bars that rise near enough to the surface of a body of water as to constitute a danger to navigation. Shoals are also known as sandbanks, sandbars, or gravelbars, two or more shoals that are either separated by shared troughs or interconnected by past and or present sedimentary and hydrographic processes are referred to as a shoal complex. The term shoal is also used in a number of ways that can be similar or quite different from how it is used in the geologic, geomorphic. Shoals are characteristically long and narrow ridges and they can develop where a stream, river, or ocean current promotes deposition of sediment and granular material, resulting in localized shallowing of the water. Marine shoals also develop either by the in place drowning of barrier islands as the result of sea level rise or by the erosion. Shoals can appear as a coastal landform in the sea, where they are classified as a type of bank, or as fluvial landforms in rivers, streams. A shoal–sandbar may seasonally separate a smaller body of water from the sea, such as, Marine lagoons Brackish water estuaries Freshwater seasonal stream and river mouths and deltas. They are typically composed of sand, although they could be of any matter that the moving water has access to and is capable of shifting around. Wave shoaling is the process when surface waves move towards shallow water, such as a beach, they slow down, their wave height increases and this behavior is called shoaling, and the waves are said to shoal. The waves may or may not build to the point where they break, depending on how large they were to begin with, in particular, waves shoal as they pass over submerged sandbanks or reefs. This can be treacherous for boats and ships, shoaling can also diffract waves, so the waves change direction. For example, if waves pass over a bank which is shallower at one end than the other. Thus the wave fronts will refract, changing direction like light passing through a prism, refraction also occurs as waves move towards a beach if the waves come in at an angle to the beach, or if the beach slopes more gradually at one end than the other. Sandbars, also known as a trough bars, form where the waves are breaking, sometimes this occurs seaward of a trough. Sand carried by the moving bottom current is deposited where the current reaches the wave break. Other longshore bars may lie further offshore, representing the point of even larger waves. A harbor or river bar is a sedimentary deposit formed at an entrance or river mouth by. Where beaches are suitably mobile, or the river’s suspended and/or bed loads are large enough, deposition can build up a sandbar that completely blocks a river mouth and damming the river
16.
Fast ice
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Fast ice is sea ice that is fastened to the coastline, to the sea floor along shoals or to grounded icebergs. Fast ice may either grow in place from the sea water or by freezing pieces of drifting ice to the shore or other anchor sites, unlike drift ice, fast ice does not move with currents and winds. The width of this ice zone is usually seasonal and depends on ice thickness, topography of the sea floor and it ranges from a few meters to several hundred kilometers. Seaward expansion is a function of a number of factors, notably water depth, shoreline protection, time of year, the topography of the fast ice varies from smooth and level to rugged. The ice foot refers to ice that has formed at the shoreline, further away from the coastline, the ice may become anchored to the sea bottom—it is then referred to as bottomfast ice. Fast ice can survive one or more melting seasons, in case it can be designated following the usual age-based categories. The fast ice boundary is the limit between fast ice and drift ice—in places, this boundary may coincide with a shear ridge, fast ice may be delimited or enclose pressure ridges which extend sufficiently downward so as to be grounded—these features are known as stamukhi. Anchor ice, also called bottom-fast ice Ice bridge Sea ice Stamukha
17.
Drift ice
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Drift ice is any sea ice other than fast ice, the latter being attached to the shoreline or other fixed objects. Drift ice is carried along by winds and sea currents, hence its name, when drift ice is driven together into a large single mass, it is called pack ice. Wind and currents can pile up that ice to form ridges up to several metres in height and these represent a challenge for icebreakers and offshore structures operating in cold oceans and seas. Drift ice consists of floes, individual pieces of sea ice 20 metres or more across. Seasonal ice drift in the Sea of Okhotsk by the northern coast of Hokkaidō, Japan has become a tourist attraction of this area with harsh climate, the Sea of Okhotsk is the southernmost area in the Northern hemisphere where drift ice may be observed. Drift ice affects, Security of navigation Climatic impact Geological impact Biosphere influence The two major ice packs are the Arctic ice pack and the Antarctic ice pack, polar packs significantly change their size during seasonal changes of the year. Because of vast amounts of water added to or removed from the oceans and atmosphere, the behavior of polar ice packs has a significant impact on global changes in climate
18.
Baffin Bay
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Baffin Bay, located between Baffin Island and the southwest coast of Greenland, is a marginal sea of the North Atlantic Ocean. It is connected to the Atlantic via Davis Strait and the Labrador Sea, the narrower Nares Strait connects Baffin Bay with the Arctic Ocean. The bay is not navigable most of the year because of the ice cover and high density of floating ice, however, a polynya of about 80,000 km2, known as the North Water, opens in summer on the north near Smith Sound. Most of the life of the bay is concentrated near that region. The International Hydrographic Organization defines the limits of Baffin Bay as follows, a line from Cape Sheridan, Grant Land to Cape Bryant, Greenland. The parallel of 70° North between Greenland and Baffin Land, the Eastern limits of the North-West Passages. The area of the bay has been inhabited since c. 500 BC, around AD1200, the initial Dorset settlers were replaced by the Thule peoples. Recent excavations also suggest that the Norse colonization of the Americas reached the shores of Baffin Bay sometime between the 10th and 14th centuries, the English explorer John Davis was the first recorded European to enter the bay, arriving in 1585. In 1612, a group of English merchants formed the Company of Merchants of London and their governor Thomas Smythe organized five expeditions to explore the northern coasts of Canada in search of a maritime passage to the Far East. Henry Hudson and Thomas Buttons explored Hudson Bay, William Gibbons Labrador, and Robert Bylot Hudson Strait, aboard the Discovery, Baffin charted the area and named Lancaster, Smith, and Jones Sounds after members of his company. By the completion of his 1616 voyage, Baffin held out no hope of an ice-free passage, over time, his account came to be doubted until it was confirmed by John Rosss 1818 voyage. More advanced scientific studies followed in 1928, in the 1930s and after World War II by Danish, currently, there are a few Inuit settlements on the Canadian coast of the bay, including Arctic Bay, Pond Inlet and Clyde River. Those settlements are accessed and supplied by air and annual sealifts, in 1975, a town was built at Nanisivik to support lead and zinc production at the Nanisivik Mine—the first Canadian mine in the Arctic. The mine was closed in 2002 due to declining resources and metal prices, whereas the town still has a functional seaport and an airport, as of the 2006 census, it has an official population of zero. Baffin Bay was the epicenter of a 7.3 magnitude earthquake in 1933 and this is the largest known earthquake north of the Arctic Circle. It caused no damage because of its location and the small number of the nearby onshore communities. The northwestern part of the bay remains one of the most seismically active regions in eastern Canada, five earthquakes of magnitude 6 have occurred here since 1933. The latest strong earthquake occurred on 15 April 2010 and had the magnitude of 5.1, Baffin Bay is an arm of the Atlantic Ocean bounded by the Baffin Island in the west, Greenland in the east, and Ellesmere Island in the north
19.
Frazil ice
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Frazil ice is a collection of loose, randomly oriented needle-shaped ice crystals in water. It resembles slush and has the appearance of being slightly oily when seen on the surface of water, Frazil ice is the first stage in the formation of sea ice. When the water begins to lose heat rapidly, the water becomes supercooled. Turbulence, caused by winds or flow from a river. The supercooled water will already be encouraging the formation of ice crystals. Ice generally floats, but due to frazil ices small size relative to current speeds, it has an ineffective buoyancy, through a process called secondary nucleation, the crystals quickly increase in number, and because of its supercooled surrounding, the crystals will continue to grow. Sometimes, the concentration is estimated to reach one million ice crystals per cubic meter, as the crystals grow in number and size, the frazil ice will begin to adhere to objects in the water, especially if the objects themselves are at a temperature below water’s freezing point. The accumulation of ice often causes flooding or damage to objects such as trash racks. Since frazil ice is found below the surface of water, it is difficult to detect its formation, usually what happens is the frazil ice accumulates on the upstream side of objects and sticks to them. The frazil ice accumulates as more gets deposited, the growth will extend upstream and increase in width until the point where the frazil ice accumulations bridge together and block the water. As more and more water flows against this block, the pressure on the upstream side increases and causes a differential pressure and this will cause the growth of the bridge to extend downstream. Once this happens, flooding and damage is likely unless otherwise prevented, Frazil ice has also been demonstrated to form beneath temperate glaciers as water flows quickly downhill and supercools due to a rapid loss of pressure. This glaciohydraulic supercooling process forms a network of platy ice crystals that can effectively trap silt from the sediment-laden water that flows beneath glaciers. There are several ways to control frazil ice build up and they include suppression, mechanical control, thermal control, vibration, materials selection and damage mitigation. Frazil ice forms in supercooled water which occurs because the water loses heat to cooler air above. Suppression is the idea of ‘insulating’ the surface water with an intact, the ice cover will prevent heat loss and warm the supercooled water that might have already formed. Sufficient area needs to be covered in order for this method to work and this final method is often not preferred because of high labour costs, cold, wet and late night working conditions. Back flushing is another technology that uses the idea of cancelling out the pressure caused by the frazil ice accumulation
20.
Slush
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Slush, also called slush ice, is a slurry mixture of small ice crystals and liquid water. In the natural environment, slush forms when ice or snow melts and this often mixes with dirt and other materials, resulting in a gray or muddy brown color. Often, solid ice or snow will block the drainage of water from slushy areas. Slushfall or slushing is the action of a wet snow falling from the sky, slush on roads can also increase the braking distances for cars and trucks, increasing the possibility of rear end crashes and other accidents. Slush refreezing in overnight frost can turn to dangerous slippery ice underfoot
21.
Grease ice
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Grease ice is a very thin, soupy layer of frazil crystals clumped together, which makes the ocean surface resemble an oil slick. Grease ice is the stage in the formation of solid sea ice after ice floes. New sea ice formation takes place throughout the winter in the Arctic, the first ice that forms in a polynya are loose ice crystals called frazil ice. If the level of turbulence is sufficient, the ice will be mixed down into the upper layer. The term ‘grease ice’ follows World Meteorological Organization nomenclature, grease ice differs from ‘slush’, where slush is similarly created by snow falling into the top layer of an ocean basin, river, or lake. When the water begins to lose heat rapidly, the water becomes supercooled. Turbulence, caused by winds or flow from a river. The supercooled water will already be encouraging the formation of ice crystals. Sea ice growth in turbulent water differs from sea ice growth in calm water, in turbulent water, the ice crystals accumulate at the surface, forming a grease-ice layer composed of individual ice crystals and small irregular clumps of ice crystals. In calm water conditions, nilas, a thick elastic crust, forms at the surface, parkinson, Claire L. Comiso, Josefino C
22.
Pancake ice
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Pancake ice is a form of ice that consists of round pieces of ice with diameters ranging from 30 centimetres to 3 metres, depending on the local conditions that affect ice formation. It may have a thickness of up to 10 centimetres, pancake ice features elevated rims formed by piling the frazil ice/slush/etc. Up the edges of pancakes when they collide, both due to bumping into each other and because of periodic compressions at wave troughs. These rims are the first indication of the onset of the formation of the ice from less consolidated forms of ice. Pancake ice may be formed in two ways and it may be formed on water covered to some degree in slush, shuga or grease ice. Alternatively, it may be created by breaking ice rind, nilas or even gray ice in the agitated conditions, definition of pancake ice from the Canadian Ice Service
23.
Arctic
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The Arctic is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Alaska, Canada, Finland, Greenland, Iceland, Norway, Russia, land within the Arctic region has seasonally varying snow and ice cover, with predominantly treeless permafrost-containing tundra. Arctic seas contain seasonal sea ice in many places, the Arctic region is a unique area among Earths ecosystems. For example, the cultures in the region and the Arctic indigenous peoples have adapted to its cold, in recent years, Arctic sea ice decline has been caused by global warming. Life in the Arctic includes organisms living in the ice, zooplankton and phytoplankton, fish and marine mammals, birds, land animals, plants, Arctic land is bordered by the subarctic. The word Arctic comes from the Greek word ἀρκτικός, near the Bear, northern, there are a number of definitions of what area is contained within the Arctic. The area can be defined as north of the Arctic Circle, the southern limit of the midnight sun. The Arctics climate is characterized by cold winters and cool summers and its precipitation mostly comes in the form of snow and is low, with most of the area receiving less than 50 cm. High winds often stir up snow, creating the illusion of continuous snowfall, average winter temperatures can be as low as −40 °C, and the coldest recorded temperature is approximately −68 °C. Coastal Arctic climates are moderated by oceanic influences, having generally warmer temperatures, the Arctic is affected by current global warming, leading to Arctic sea ice shrinkage, diminished ice in the Greenland ice sheet, and Arctic methane release as the permafrost thaws. Due to the migration of the planets isotherms, the Arctic region is currently shrinking. Perhaps the most spectacular result of Arctic shrinkage is sea ice loss, there is a large variance in predictions of Arctic sea ice loss, with models showing near-complete to complete loss in September from 2040 to some time well beyond 2100. About half of the models show near-complete to complete sea ice loss in September by the year 2100. Arctic life is characterized by adaptation to short growing seasons with long periods of sunlight, Arctic vegetation is composed of plants such as dwarf shrubs, graminoids, herbs, lichens and mosses, which all grow relatively close to the ground, forming tundra. As one moves northward, the amount of available for plant growth decreases considerably. Colder summer temperatures cause the size, abundance, productivity and variety of plants to decrease, trees cannot grow in the Arctic, but in its warmest parts, shrubs are common and can reach 2 m in height, sedges, mosses and lichens can form thick layers. In the coldest parts of the Arctic, much of the ground is bare, non-vascular plants such as lichens and mosses predominate, along with a few scattered grasses, herbivores on the tundra include the Arctic hare, lemming, muskox, and caribou. They are preyed on by the owl, Arctic fox, Grizzly bear
24.
Antarctic
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The Antarctic is a polar region, specifically the region around the Earths South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises in the sense the continent of Antarctica. The region covers some 20% of the Southern Hemisphere, of which 5. 5% is the area of the Antarctic continent itself. All of the land and ice shelves south of 60°S latitude are administrated under the Antarctic Treaty System, in a biogeographic sense, the Antarctic ecozone is one of eight ecozones of the Earths land surface. Most of the Antarctic region is situated south of 60°S latitude parallel, there are only two species of flowering plant, Antarctic hair grass and Antarctic pearlwort, but a range of mosses, liverworts, lichens and macrofungi. The first Antarctic land discovered was the island of South Georgia, the first human born in the Antarctic was Solveig Gunbjørg Jacobsen born on 8 October 1913 in Grytviken, South Georgia. However, the region is visited by more than 40,000 tourists annually, the definitive results of the conference was presented at the Antarctic Treaty states meeting in Uruguay in May 2010. The Antarctic hosts the worlds largest protected area comprising 1.07 million km2, the South Georgia, because Antarctica surrounds the South Pole, it is theoretically located in all time zones. For practical purposes, time zones are based on territorial claims or the time zone of a stations owner country or supply base. Antarctic Circle History of Antarctica Krupnik, Igor, Michael A. Lang, smithsonian at the Poles, Contributions to International Polar Year Science
25.
Coriolis force
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In physics, the Coriolis force is an inertial force that acts on objects that are in motion relative to a rotating reference frame. In a reference frame with clockwise rotation, the acts to the left of the motion of the object. In one with anticlockwise rotation, the acts to the right. Early in the 20th century, the term Coriolis force began to be used in connection with meteorology, deflection of an object due to the Coriolis force is called the Coriolis effect. Newtons laws of motion describe the motion of an object in a frame of reference. When Newtons laws are transformed to a frame of reference. Both forces are proportional to the mass of the object, the Coriolis force is proportional to the rotation rate and the centrifugal force is proportional to its square. The Coriolis force acts in a perpendicular to the rotation axis. The centrifugal force acts outwards in the direction and is proportional to the distance of the body from the axis of the rotating frame. These additional forces are termed inertial forces, fictitious forces or pseudo forces and they allow the application of Newtons laws to a rotating system. They are correction factors that do not exist in a non-accelerating or inertial reference frame, a commonly encountered rotating reference frame is the Earth. The Coriolis effect is caused by the rotation of the Earth, such motions are constrained by the surface of the Earth, so only the horizontal component of the Coriolis force is generally important. This force causes moving objects on the surface of the Earth to be deflected to the right in the Northern Hemisphere, the horizontal deflection effect is greater near the poles, since the effective rotation rate about a local vertical axis is largest there, and smallest at the equator. This effect is responsible for the rotation of large cyclones, riccioli, Grimaldi, and Dechales all described the effect as part of an argument against the heliocentric system of Copernicus. In other words, they argued that the Earths rotation should create the effect, the effect was described in the tidal equations of Pierre-Simon Laplace in 1778. Gaspard-Gustave Coriolis published a paper in 1835 on the yield of machines with rotating parts. That paper considered the forces that are detected in a rotating frame of reference. Coriolis divided these forces into two categories
26.
Shear (geology)
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Shear is the response of a rock to deformation usually by compressive stress and forms particular textures. Shear can be homogeneous or non-homogeneous, and may be pure shear or simple shear, study of geological shear is related to the study of structural geology, rock microstructure or rock texture and fault mechanics. The process of shearing occurs within brittle, brittle-ductile, and ductile rocks, within purely brittle rocks, compressive stress results in fracturing and simple faulting. Rocks typical of shear zones include mylonite, cataclasite, S-tectonite and L-tectonite, pseudotachylite, certain breccias, a shear zone is a tabular to sheetlike, planar or curviplanar zone composed of rocks that are more highly strained than rocks adjacent to the zone. Typically this is a type of fault, but it may be difficult to place a distinct fault plane into the shear zone, shear zones may form zones of much more intense foliation, deformation, and folding. En echelon veins or fractures may be observed within shear zones, many shear zones host ore deposits as they are a focus for hydrothermal flow through orogenic belts. They may often show some form of metamorphism from a peak metamorphic assemblage and are commonly metasomatised. Shear zones can be only inches wide, or up to several kilometres wide, often, due to their structural control and presence at the edges of tectonic blocks, shear zones are mappable units and form important discontinuities to separate terranes. As such, many large and long shear zones are named, when the horizontal displacement of this faulting can be measured in the tens or hundreds of kilometers of length, the fault is referred to as a megashear. Megashears often indicate the edges of ancient tectonic plates, the mechanisms of shearing depend on the pressure and temperature of the rock and on the rate of shear which the rock is subjected to. The response of the rock to these conditions determines how it accommodates the deformation, shear zones accommodate compressive stress by movement on foliation planes. Shearing at ductile conditions may occur by fracturing of minerals and growth of sub-grain boundaries and this occurs particularly on platy minerals, especially micas. Mylonites are essentially ductile shear zones, during the initiation of shearing, a penetrative planar foliation is first formed within the rock mass. This manifests as realignment of textural features, growth and realignment of micas, the incipient shear foliation typically forms normal to the direction of principal shortening, and is diagnostic of the direction of shortening. In symmetric shortening, objects flatten on this shear foliation much the way that a round ball of treacle flattens with gravity. Within asymmetric shear zones, the behavior of an object undergoing shortening is analogous to the ball of treacle being smeared as it flattens, within shear zones with pronounced displacements a shear foliation may form at a shallow angle to the gross plane of the shear zone. This foliation ideally manifests as a set of foliations formed at a shallow angle to the main shear foliation. Such rocks are known as L-S tectonites, if the rock mass begins to undergo large degrees of lateral movement, the strain ellipse lengthens into a cigar shaped volume
27.
Finger rafting
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Finger rafting develops in an ice cover as a result of a compression regime established within the plane of the ice. As two expanses of sea ice converge toward another, one of them slides smoothly on top of the other along a given distance, the term finger rafting refers to the systematic alternation of interlocking overthrusts and underthrusts involved in this process. Such a pattern derives its name from its resemblance to the interlocking of fingers, rafting, also called telescoped ice, is most noticeable when it involves new and young ice, but also occurs in ice of all thicknesses. The process of finger rafting as such is commonly observed inside a lead, although this ice is typically very weak, it contains a lot of brine and is also relatively warm, since being that thin, its temperature is near that of the water. Rafting is accompanied with rapid draining of the brine inside the ice sheet. This brine acts as a lubricant, significantly reducing the friction between the two sheets during overthrusting, such a mechanism, and the fact that the upper surface of nilas is already slippery, account for overthrust distances in excess of 100 metres. Rafting and ridging are two possible responses expected from the interaction between two converging ice sheets or floes, the term ‘ridging’ refers to the process of ridge formation, involving the breaking up of the ice sheet into distinct blocks. The reason why breaking happens is that, as the ice thickness increases, in other words, the ice is no longer flexible enough to withstand the overthrust event without breaking. A theoretical formula has been used to estimate the maximum thickness an ice sheet can have in order to be able to raft. What this equation shows is that, assuming a representative tensile strength of 0.65 MPa, the maximum thickness for rafting to occur is in the range of 0.2 metres
28.
Pressure ridge (ice)
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A pressure ridge develops in an ice cover as a result of a stress regime established within the plane of the ice. Within sea ice expanses, pressure ridges originate from the interaction between floes, as they collide with each other, currents and winds are the main driving forces, but the latter are particularly effective when they have a predominant direction. Pressure ridges are made up of ice blocks of various sizes that pile up on the floes. The part of the ridge that is above the surface is known as the sail. Pressure ridges are the thickest sea ice features and account for about one-half of the sea ice volume. Stamukhi are pressure ridges that are grounded and that result from the interaction between fast ice and the pack ice. The blocks making up pressure ridges are mostly from the ice floe involved in the interaction. In the summer, the ridge can undergo a significant amount of weathering, during this process, the ice loses its salinity. This is known as an aged ridge, a consolidated ridge is one whose base has undergone complete freezing. The term consolidated layer is used to designate freezing up of the rubble just below the water line, a keels depth of an ice ridge is much higher than its sails height - typically about four times. The keel is also 2-3 times wider than the sail, one of the largest pressure ridges on record had a sail extending 12 metres above the water surface, and a keel depth of 45 metres. The total thickness for a ridge was reported to be 40 metres. On average, total thickness ranges between 5 metres and 30 metres, with a mean sail height that remains below 2 metres, surveying, whereby a level, theodolite or a differential GPS system is used to determine sail geometry. Thermal drilling – drilling involving melting of the ice, observation of the ice canopy by scuba divers. A series of thermistors, to temperature changes. Electromagnetic induction, from the ice surface or from an aircraft, from an offshore engineering and naval perspective, there are three reasons why pressure ridges are a subject of investigation. Firstly, because the highest loads applied on offshore structures operating in cold oceans by drift ice are associated with these features. Secondly, when pressure ridges drift into shallower areas, their keel may come into contact with the seabed, thereby representing a risk for subsea pipelines, thirdly, they have a significant impact on navigation
29.
Hummock
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A hummock is a small knoll or mound above ground. They are typically less than 15 meters in height and tend to appear in groups or fields and 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, an ice hummock is a boss or rounded knoll of ice rising above the general level of an ice-field. Hummocky ice is caused by slow and unequal pressure in the body of the packed ice. Hummocks in the shape of low ridges of drier peat moss typically form part of the structure of certain types of raised bog, such as plateau, kermi, the hummocks alternate with shallow wet depressions or flarks. Swamp hummocks are mounds typically initiated as fallen trunks or branches covered with moss, the low-lying areas between hummocks are called hollows. A related term, used in the Southeastern United States, is hammock, cryogenic earth hummocks go by many different names, in North America they are earth hummocks, thúfur in Greenland and Iceland, and pounus in Fennoscandia. These cold climate landforms appear in regions of permafrost and seasonally frozen ground and they usually develop in fine-grained soils with light to moderate vegetation in areas of low relief where there is adequate moisture to fuel cryogenic processes. Cryogenic earth hummocks appear in a variety of environments, making the story of their genesis complex. Geologists recognize that hummocks may be polygenetic and form by a combination of forces that are yet to be well understood, recent research on cryogenic hummocks has focused on their role as environmental indicators. Because hummocks can both form and disintegrate rapidly they are an ideal landform to monitor for medium range environmental change, there are several explanations of earth hummock formation. Hummocks may form as a result of migrating to the surface through frost push. As the clasts rise they push up on the ground above forming bulging mounds, Hummock excavation normally reveals a disturbed soil profile, often with irregular streaks of organic matter or other colorations suggesting fluidity at some time past. The disturbance, a form of cryoturbation often extends to a roughly equal to the hummock’s height. This has been explained by some as the result of convection processes whereby warmer soil and water at depth expands, becomes less dense and rises, circulation has also been explained as driven solely by density of soil material, not temperature induced density changes. This is the most widely accepted explanation of cryogenic hummock genesis, irregularities in preexisting ground conditions cause surface downwards freezing during the winter to spread unevenly. Encroaching frost exerted increasing pressure on the adjacent unfrozen soil, trapped between the freezing surface soils and the buried permafrost layer the soil material is forced upwards into hummocks. While this is currently the most commonly accepted hypothesis, there is only limited evidence of this happening
30.
Stamukha
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A stamukha is a grounded accumulation of sea ice rubble that typically develops along the boundary between fast ice and the drifting pack ice, or becomes incorporated into the fast ice. Wind, currents and tides contribute to this phenomenon, stamukhi tend to occur in belts that are parallel to the shoreline, along coastal shoals, at water depths of about 20 m, but that can reach 50 m. They can build up to heights 10 metres or more above the waterline, although they remain pinned to the seabed, these features can be subject to small displacements, either due to thermal expansion or to the pressure exerted by the drifting pack ice onto the fast ice. Because stamukhi tend to be grounded, they may occur as isolated ice features in the open sea during the summer season. Since stamukhi extend downward into the seabed, they present a risk to submarine pipelines, seabed penetration by the ice can reach a depth of 5 metres
31.
Lead (sea ice)
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A lead is a large fracture within an expanse of sea ice, defining a linear area of open water that can be used for navigation purposes. Leads vary in width from meters to hundreds of meters, as is the case for polynyas, leads allow the direct interaction between the atmosphere and the ocean, and are important for Arctic sea ice ecology. Additionally it has been found that ice leads contribute significantly to the amount of mercury deposited onto surface. If the air is cold enough, the water within a lead quickly refreezes, such that in many cases, unlike polynyas, which tend to occur, and remain, at a given location, leads are transient features that can form anywhere in an ice-covered ocean. Lead formation is therefore tied in with synoptic-scale weather patterns, typically lasting a few days, Sea ice is often classified according to whether or not it is attached to the shoreline. If attached, it is called land fast ice, otherwise, it is called drift ice and is free to move with currents and winds. This is why leads typically belong to the ice zone. They are seen as a stress relieving mechanism, in response to divergent current flows or the effects of wind, leads are cracks or fissures that initiate inside an otherwise continuous sea ice cover, and open up progressively afterward. They are linear features, though generally not rigorously straight, as they may comprise any number of short offsets at an angle with the trend of the initial crack. This crack may cut right across both thin and thick ice, depending on the state of stress within the drift zone, leads may also close up. As the two sides converge back toward each other, this can lead to finger rafting of the new ice inside the lead. Once a crack occurs within the ice cover and begins to expand to make up a lead, because wind fetch inside a lead is typically very short, wave action is considerably reduced. Ice growth therefore takes place in a low energy regime environment, following a stage of frazil ice formation, which sometimes results from seeding by snow crystals, the resulting thin ice skim is followed by the growth of congelation ice. In windier regions, as in the Southern Ocean, frazil ice accumulation may occur along the side of leads. If the ice on that side is thin, the frazil may be driven below that ice, as ice begins to form inside a lead, it incorporates some of the salt in the seawater but rejects most of it. This brine then sinks, inducing convective processes in the column below. There are a few types of leads, A blind lead is a lead that is closed off – both ends terminate within the ice zone. A flaw lead is a lead that forms between the fast ice zone and the ice zone
32.
Polynya
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A polynya /pəˈlɪnjə/ is an area of open water surrounded by sea ice. It is now used as term for an area of unfrozen sea within the ice pack. It is a loanword from Russian, полынья Russian pronunciation, which refers to an ice hole. In past decades, for example, some polynyas, such as the Weddell Polynya, have lasted over multiple winters and this reduces ice production and may stop it altogether. Latent heat polynya, is formed through the action of wind or ocean currents which act to drive ice away from a fixed boundary, such as a coastline, fast ice. The polynya forms initially by the first year pack ice being driven away from the coast and this new ice is then also herded downwind toward the first year pack ice. When it reaches the ice the new ice is consolidated onto the pack ice. The latent heat polynya is the water region between the coast and the ice pack. Latent heat polynyas are regions of ice production and therefore are possible sites of dense water production in both polar regions. The high ice production rates within these polynyas leads to an amount of brine rejection into the surface waters. This salty water then sinks and mixes to possibly form new water masses and it is an open question as to whether the polynyas of the Arctic can produce enough dense water to form a major portion of the dense water required to drive the thermohaline circulation. Some polynyas, such as the North Water Polynya between Canada and Greenland occur seasonally at the time and place each year. Because animals can adapt their strategies to this regularity, these types of polynyas are of special ecological research significance. In winter, marine mammals such as walruses, narwhals and belugas that do not migrate south, polar bears are known to be able to swim as far as 65 kilometres across open waters of a polynya. The presence of polynyas in McMurdo Sound in the Antarctic provides an area where penguins can feed. When submarines of the U. S. Navy made expeditions to the North Pole in the 1950s and 60s, there was a significant concern about surfacing through the thick pack ice of the Arctic Ocean. In 1962, both the USS Skate and USS Seadragon surfaced within the same, large polynya near the North Pole, lead North Water Polynya Weddell Polynya International North Water Polynya Study Polynya north of Alaska at NASA Earth Observatory
33.
Lead
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Lead is a chemical element with atomic number 82 and symbol Pb. When freshly cut, it is bluish-white, it tarnishes to a dull gray upon exposure to air and it is a soft, malleable, and heavy metal with a density exceeding that of most common materials. Lead has the second-highest atomic number of the stable elements. Lead is a relatively unreactive post-transition metal and its weak metallic character is illustrated by its amphoteric nature and tendency to form covalent bonds. Compounds of lead are found in the +2 oxidation state. Exceptions are mostly limited to organolead compounds, like the lighter members of the group, lead exhibits a tendency to bond to itself, it can form chains, rings, and polyhedral structures. Lead is easily extracted from its ores and was known to people in Western Asia. A principal ore of lead, galena, often bears silver, Lead production declined after the fall of Rome and did not reach comparable levels again until the Industrial Revolution. Nowadays, global production of lead is about ten million tonnes annually, Lead has several properties that make it useful, high density, low melting point, ductility, and relative inertness to oxidation. In the late 19th century, lead was recognized as poisonous, Lead is a neurotoxin that accumulates in soft tissues and bones, damaging the nervous system and causing brain disorders and, in mammals, blood disorders. A lead atom has 82 electrons, arranged in a configuration of 4f145d106s26p2. The combined first and second ionization energies—the total energy required to remove the two 6p electrons—is close to that of tin, leads upper neighbor in group 14. This is unusual since ionization energies generally fall going down a group as an elements outer electrons become more distant from the nucleus, the similarity is caused by the lanthanide contraction—the decrease in element radii from lanthanum to lutetium, and the relatively small radii of the elements after hafnium. The contraction is due to shielding of the nucleus by the lanthanide 4f electrons. The combined first four ionization energies of lead exceed those of tin, for this reason lead, unlike tin, mostly forms compounds in which it has an oxidation state of +2, rather than +4. Relativistic effects, which become particularly prominent at the bottom of the periodic table, as a result, the 6s electrons of lead become reluctant to participate in bonding, a phenomenon called the inert pair effect. A related outcome is that the distance between nearest atoms in crystalline lead is unusually long, the lighter group 14 elements form stable or metastable allotropes having the tetrahedrally coordinated and covalently bonded diamond cubic structure. The energy levels of their outer s- and p-orbitals are close enough to allow mixing into four hybrid sp3 orbitals
34.
Sea ice growth processes
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Sea ice is a complex composite composed primarily of pure ice in various states of crystallization along with air bubbles and included pockets of brine. Sea ice growth models for predicting the ice distribution and extent are also valuable for shipping concerns, an ice growth model can be combined with remote sensing measurements in an assimilation model as a means of generating more accurate ice charts. Several formation mechanisms of sea ice have been identified, at its earliest stages, sea ice consists of elongated, randomly oriented crystals. This is called frazil and mixed with water in the state is known as grease ice. If wave and wind conditions are calm, these crystals will consolidate at the surface and by pressure, begin to grow preferentially in the downward direction. Subsequent freezing will form ice with a more granular structure. One of the more interesting processes to occur within consolidated ice packs is changes in the saline content, as the ice freezes, most of the salt content gets rejected and forms highly saline brine inclusions between the crystals. With decreasing temperatures in the ice sheet, the size of the brine pockets decreases while the content goes up. Brine will also drain through vertical channels, particularly in the melt season. The net heat flux is a total over four components, Q ∗ = Q E + Q H + Q L W + Q S W which are latent, sensible, longwave and shortwave fluxes, respectively. For a description of the approximate parameterizations, see determining surface flux under sea ice thickness, the equation can be solved using a numerical root-finding algorithm such as bisection, the functional dependencies on surface temperature are given, with e being the equilibrium vapor pressure. While Cox and Weeks assume thermal equilibrium, Tonboe uses a more complex thermodynamic model based on solution of the heat equation. This would be appropriate when the ice is thick or the conditions are changing rapidly. The rate of ice growth can be calculated from heat flux by the equation, g = Q ∗ L ρ where L is the latent heat of fusion for water. The growth rate in turn determines the content of the newly frozen ice. g. F =0.120.12 +0.88 exp where g is in cm/s. Brine entrapped in sea ice will always be at or near freezing since any departure will either cause some of the water in the brine to freeze, thus, brine salinity is variable and can be determined based strictly on temperature—see freezing point depression. References and contain empirical formulas relating sea ice temperature to brine salinity, the relative brine volume, Vb, is defined as the fraction of brine relative to the total volume
35.
St. Matthew Island
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St. Matthew Island is a remote island in the Bering Sea in Alaska,295 km WNW of Nunivak Island. The island has an area of 137.857 sq mi. Its most southerly point is Cape Upright which features cliff faces which exceed 1,000 feet, similar heights are found at Glory of Russia Cape on the north, and the highest point,1,476 feet above sea level, lies south from the island center. There is an island off its northwestern point called Hall Island. The 3.1 miles wide sound between both islands is called Sarichef Strait, a small rocky islet called Pinnacle Rock lies 9.3 miles to the south of Saint Matthew Island. The entire islands natural scenery and wildlife is protected as it is part of the Bering Sea unit of the Alaska Maritime National Wildlife Refuge. The United States Coast Guard maintained a manned LORAN station on the island during the 1940s.2 °C and annual precipitation of 389 mm, in prehistory, the island was inhabited by members of the Aleut tribe. The first recorded attempt at settlement occurred in 1809, when a Russian group led by Demid Ilyich Kulikalov, under the guise of the Russian-American Company, established an experimental outpost. Presently, Arctic foxes and insular voles are the only mammals resident on the island, notably, St. Matthew Island represents the southern limit of the range of polar bears in the Bering Sea. In 1944,29 reindeer were introduced to the island by the United States Coast Guard to provide a food source. The Coast Guard abandoned the island a few later, leaving the reindeer. Subsequently, the population rose to about 6,000 by 1963. A scientific study attributed the crash to the limited food supply in interaction with climatic factors. By the 1980s, the population had completely died out. Environmentalists see this as an issue of overpopulation, there are two major lakes on the island, North Lake and Big Lake. The lakes contain a number of fish species than other nearby islands. Lichen studies were conducted on the island in the 1990s to prepare a list of lichens with their habitat and these studies were considered important for characterizing the eating habits of caribou and air quality. The vegetation of the islands has been classified as wet, moist and alpine tundra, based on landforms, the plant communities were attributed to five categories
36.
Supercooling
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Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid. A liquid crossing its standard freezing point will crystalize in the presence of a crystal or nucleus around which a crystal structure can form creating a solid. Lacking any such nuclei, the phase can be maintained all the way down to the temperature at which crystal homogeneous nucleation occurs. Homogeneous nucleation can occur above the transition temperature, but if homogeneous nucleation has not occurred above that temperature. Water normally freezes at 273.15 K, but it can be supercooled at standard pressure down to its homogeneous nucleation at almost 224.8 K. If water is cooled at a rate on the order of 106 K/s, the crystal nucleation can be avoided and water becomes a glass — that is and its glass transition temperature is much colder and harder to determine, but studies estimate it at about 136 K. Glassy water can be heated up to approximately 150 K without nucleation occurring, in the range of temperatures between 231 K and 150 K, experiments find only crystal ice. Droplets of supercooled water often exist in stratiform and cumulus clouds, Freezing rain is also caused by supercooled droplets. The process opposite to supercooling, the melting of a solid above the point, is much more difficult. It is possible, at a pressure, to superheat a liquid above its boiling point without it becoming gaseous. Supercooling is often confused with freezing-point depression, supercooling is the cooling of a liquid below its freezing point without it becoming solid. Constitutional supercooling, which occurs during solidification, is due to compositional solid changes, when solidifying a liquid, the interface is often unstable, and the velocity of the solid–liquid interface must be small in order to avoid constitutional supercooling. Supercooled zones are observed when the temperature gradient at the interface is larger than the temperature gradient. Therefore, the thermal gradient necessary to create a stable solid front is as expressed below. ∂ T ∂ x < m C0 v k D For more information, the authors are confusing supercooling with freezing-point depression. The paragraphs above warn about this confusion, in order to survive extreme low temperatures in certain environments, some animals undergo forms of supercooling that allow them to remain unfrozen and avoid cell damage and death. The winter flounder is one fish that utilizes these proteins to survive in its frigid environment. Noncolligative proteins are secreted by the liver into the bloodstream, other animals use colligative antifreezes, which increases the concentration of solutes in their bodily fluids, thus lowering their freezing point
37.
Snow
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Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, snowflakes take on a variety of shapes, basic among these are platelets, needles, columns and rime. As snow accumulates into a snowpack, it may blow into drifts, over time, accumulated snow metamorphoses, by sintering, sublimation and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form, otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater. Major snow-prone areas include the regions, the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture. In the Southern Hemisphere, snow is confined primarily to mountainous areas, Snow affects ecosystems, as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold. Snow develops in clouds that themselves are part of a weather system. The physics of snow crystal development in clouds results from a set of variables that include moisture content. The resulting shapes of the falling and fallen crystals can be classified into a number of shapes and combinations. Occasionally, some plate-like, dendritic and stellar-shaped snowflakes can form under clear sky with a cold temperature inversion present. Two additional and locally productive sources of snow are lake-effect storms and elevation effects, miid-latitude cyclones are low pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards. During a hemispheres fall, winter, and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall, in the Northern Hemisphere, the northern side of the low pressure area produces the most snow. For the southern mid-latitudes, the side of a cyclone that produces the most snow is the southern side, a cold front, the leading edge of a cooler mass of air, can produce frontal snowsqualls—an intense frontal convective line, when temperature is near freezing at the surface. The strong convection that develops has enough moisture to produce whiteout conditions at places which line passes over as the wind causes intense blowing snow. This type of snowsquall generally lasts less than 30 minutes at any point along its path, in cases where there is a large amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed thundersnow. A warm front can produce snow for a period, as warm, moist air overrides below-freezing air, often, snow transitions to rain in the warm sector behind the front. The same effect occurs over bodies of salt water, when it is termed ocean-effect or bay-effect snow. The effect is enhanced when the air mass is uplifted by the orographic influence of higher elevations on the downwind shores
38.
Ocean
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An ocean is a body of saline water that composes much of a planets hydrosphere. On Earth, an ocean is one of the major divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern, the word sea is often used interchangeably with ocean in American English but, strictly speaking, a sea is a body of saline water partly or fully enclosed by land. The ocean contains 97% of Earths water, and oceanographers have stated that less than 5% of the World Ocean has been explored, the total volume is approximately 1.35 billion cubic kilometers with an average depth of nearly 3,700 meters. As the world ocean is the component of Earths hydrosphere, it is integral to all known life, forms part of the carbon cycle. The world ocean is the habitat of 230,000 known species, but because much of it is unexplored, the origin of Earths oceans remains unknown, oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of water or other elements and compounds, the only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many planets and natural satellites, notably. The Solar Systems giant planets are thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of water within a circumstellar habitable zone. Ocean planets are a type of planet with a surface completely covered with liquid. The concept of Ōkeanós has an Indo-European connection, Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases, though generally described as several separate oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a body of water with relatively free interchange among its parts is of fundamental importance to oceanography. The major oceanic divisions – listed below in descending order of area and volume – are defined in part by the continents, various archipelagos, Oceans are fringed by smaller, adjoining bodies of water such as seas, gulfs, bays, bights, and straits. The Mid-Oceanic Ridge of the World are connected and form the Ocean Ridge, the continuous mountain range is 65,000 km long, and the total length of the oceanic ridge system is 80,000 km long
39.
Antarctica
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It contains the geographic South Pole and is situated in the Antarctic region of the Southern Hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean. At 14,000,000 square kilometres, it is the fifth-largest continent, for comparison, Antarctica is nearly twice the size of Australia. About 98% of Antarctica is covered by ice that averages 1.9 km in thickness, Antarctica, on average, is the coldest, driest, and windiest continent, and has the highest average elevation of all the continents. Antarctica is a desert, with precipitation of only 200 mm along the coast. The temperature in Antarctica has reached −89.2 °C, though the average for the quarter is −63 °C. Anywhere from 1,000 to 5,000 people reside throughout the year at the research stations scattered across the continent. Organisms native to Antarctica include many types of algae, bacteria, fungi, plants, protista, vegetation, where it occurs, is tundra. The continent, however, remained neglected for the rest of the 19th century because of its hostile environment, lack of easily accessible resources. In 1895, the first confirmed landing was conducted by a team of Norwegians, Antarctica is a de facto condominium, governed by parties to the Antarctic Treaty System that have consulting status. Twelve countries signed the Antarctic Treaty in 1959, and thirty-eight have signed it since then, the treaty prohibits military activities and mineral mining, prohibits nuclear explosions and nuclear waste disposal, supports scientific research, and protects the continents ecozone. Ongoing experiments are conducted by more than 4,000 scientists from many nations, the name Antarctica is the romanised version of the Greek compound word ἀνταρκτική, feminine of ἀνταρκτικός, meaning opposite to the Arctic, opposite to the north. Aristotle wrote in his book Meteorology about an Antarctic region in c.350 B. C, marinus of Tyre reportedly used the name in his unpreserved world map from the 2nd century A. D. Before acquiring its present geographical connotations, the term was used for locations that could be defined as opposite to the north. For example, the short-lived French colony established in Brazil in the 16th century was called France Antarctique, the first formal use of the name Antarctica as a continental name in the 1890s is attributed to the Scottish cartographer John George Bartholomew. Antarctica has no population and there is no evidence that it was seen by humans until the 19th century. Explorer Matthew Flinders, in particular, has credited with popularising the transfer of the name Terra Australis to Australia. Cook came within about 120 km of the Antarctic coast before retreating in the face of ice in January 1773. The first confirmed sighting of Antarctica can be narrowed down to the crews of ships captained by three individuals, according to various organisations, ships captained by three men sighted Antarctica or its ice shelf in 1820, von Bellingshausen, Edward Bransfield, and Nathaniel Palmer
40.
Russia
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Russia, also officially the Russian Federation, is a country in Eurasia. The European western part of the country is more populated and urbanised than the eastern. Russias capital Moscow is one of the largest cities in the world, other urban centers include Saint Petersburg, Novosibirsk, Yekaterinburg, Nizhny Novgorod. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a range of environments. It shares maritime borders with Japan by the Sea of Okhotsk, the East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, in 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus ultimately disintegrated into a number of states, most of the Rus lands were overrun by the Mongol invasion. The Soviet Union played a role in the Allied victory in World War II. The Soviet era saw some of the most significant technological achievements of the 20th century, including the worlds first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the second largest economy, largest standing military in the world. It is governed as a federal semi-presidential republic, the Russian economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2015. Russias extensive mineral and energy resources are the largest such reserves in the world, making it one of the producers of oil. The country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction, Russia is a great power as well as a regional power and has been characterised as a potential superpower. The name Russia is derived from Rus, a state populated mostly by the East Slavs. However, this name became more prominent in the later history, and the country typically was called by its inhabitants Русская Земля. In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus by modern historiography, an old Latin version of the name Rus was Ruthenia, mostly applied to the western and southern regions of Rus that were adjacent to Catholic Europe. The current name of the country, Россия, comes from the Byzantine Greek designation of the Kievan Rus, the standard way to refer to citizens of Russia is Russians in English and rossiyane in Russian. There are two Russian words which are translated into English as Russians
41.
Vladimir Wiese
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Vladimir Yulyevich Vize, was a Russian scientist of German descent who devoted his life to the study of the Arctic ice pack. His name is associated with the Scientific Prediction of Ice Conditions theory, Vize was a member of the Soviet Arctic Institute and an authority on polar oceanography. He was also the founder of the Geographico-hydrological School of Oceanography, Vize went with G. L. Sedov’s expedition on St. Foka to Novaya Zemlya and Franz Josef Land. After the Russian Revolution Professor Vize went on a number of Soviet Arctic expeditions, in 1924 oceanographer Vize, studied the drift of Georgy Brusilovs ill-fated Russian ship St. Anna when she was trapped on the pack ice of the Kara Sea. Professor Vize detected an odd deviation of the path of the ships drift caused by variations of the patterns of sea. The data of the drift had been supplied by navigator Valerian Albanov, finally the island was discovered on 13 August 1930 by a Soviet expedition led by Otto Schmidt aboard the Icebreaker Sedov under Captain Vladimir Voronin. The island was named Vize Island after Professor Vize who was at the time aboard the Sedov, in July 1931 Professor V. Yu. Vize led an expedition on icebreaking steamer Malygin to Franz Josef Land and he carried out meteorological, electromagnetic and hydrological observations during this expedition, along with other scientists, like N. V. Pinegin and R. V. Khutsishvili. Other members included technicians whose mission was to locate a place for a Soviet floatplane base in Franz Josef Land. Captain D. T. Chertkhov was in command of the icebreaker, during this expedition German airship Graf Zeppelin made a rendezvous with icebreaker Malygin at Bukhta Tikhaya in Hooker Island, Franz Josef Land. At Rudolf Island Professor Vize and N. V. Pinegin recovered artifacts from the huts of the 1904–1905 Ziegler-Fiala Polar Expedition to Zemlya Frantsa Josifa. His intention was to carry out oceanographic research in the Arctic basin, but owing to fog and bad weather he reluctantly gave up. In this Arctic expedition Professor Vize’s scientific zeal was tempered by Captain Chertkhovs prudent decisions, even so, the expedition was quite successful. Surface water temperatures were taken at 295 locations, water samples were taken from 273 stations, in 1937 Professor Vize went on Soviet icebreaker Sadko with R. L. Lazarevich and N. Evgenov on an expedition. Its goal was to sail to Henrietta, Zhokhov and Jeannette Islands, in the De Long group, the purpose of the expedition was also to find out how could the Northern Sea Route be used for regular shipping. But the Soviet naval authorities changed the plans and the ice-breaker was sent instead to help ships in distress in the Kara, the Sadko, however, became itself trapped in fast ice at 75°17N and 132°28E in the region of the New Siberian Islands. Two other Soviet icebreakers, the Sedov and the Malygin who were in the same area researching the ice conditions, became trapped by sea ice as well and drifted helplessly. Owing to persistent bad weather conditions, part of the crew members
42.
Kara Sea
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The Kara Sea is part of the Arctic Ocean north of Siberia. It is separated from the Barents Sea to the west by the Kara Strait and Novaya Zemlya, and it is named for the Kara River, which is now relatively insignificant but which played an important role in the Russian conquest of northern Siberia. The word kara is derived from kara, which in several Turkic languages means black, the Kara Sea is roughly 1,450 kilometres long and 970 kilometres wide with an area of around 880,000 km2 and a mean depth of 110 metres. Compared to the Barents Sea, which receives relatively warm currents from the Atlantic, the Kara receives a large amount of fresh water from the Ob, Yenisei, Pyasina, and Taimyra rivers, so its salinity is variable. Its main ports are Novy Port and Dikson and it is important as a fishing ground although the sea is ice-bound for all but two months of the year. Significant discoveries of petroleum and natural gas, the East-Prinovozemelsky field, in 2014, US government sanctions resulted in Exxon having until September 26 to discontinue its operations in the Kara Sea. The International Hydrographic Organization defines the limits of the Kara Sea as follows, the Eastern limit of Barentsz Sea. Komsomolets Island from Cape Molotov to South Eastern Cape, thence to Cape Vorochilov, then to Cape Unslicht on Bolshevik Island. Thence to Cape Pronchisthehev on the main land, there are many islands and island groups in the Kara Sea. The largest group in the Kara Sea is by far the Nordenskiöld Archipelago, with five large subgroups, other important islands in the Kara Sea are Bely Island, Dikson Island, Taymyr Island, the Kamennyye Islands and Oleni Island. Despite the high latitude all islands are unglaciated except for Ushakov Island at the northern limit of the Kara Sea. The Kara Sea was formerly known as Oceanus Scythicus or Mare Glaciale, since it is closed by ice most of the year it remained largely unexplored until the late nineteenth century. In 1556 Stephen Borough sailed in the Searchthrift to try to reach the Ob River, not until 1580 did another English expedition, under Arthur Pet and Charles Jackman, attempt its passage. They too failed to penetrate it, and England lost interest in searching for the Northeast Passage, in 1736–1737 Russian Admiral Stepan Malygin undertook a voyage from Dolgy Island in the Barents Sea. The two ships in this expedition were the Perviy, under Malygins command and the Vtoroy under Captain A. Skuratov. After entering the little-explored Kara Sea, they sailed to the mouth of the Ob River, Malygin took careful observations of these hitherto almost unknown areas of the Russian Arctic coastline. With this knowledge he was able to draw the first somewhat accurate map of the Arctic shores between the Pechora River and the Ob River, frozen in for the winter in the Chukchi Sea, Nordenskiöld waited and bartered with the local Chukchi people. The following July, the Vega was freed from the ice and he became the first to force the Northeast Passage
43.
Vize Island
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Vize Island or Wiese Island, also known as Zemlya Vize is an isolated island located in the Arctic Ocean, Russian Federation. This island is desolate and subject to severe Arctic storms, in the summer, large areas of the island are free of ice and snow. Its total area is 288 km2, compared to other Arctic islands it is relatively large and flat, its highest point being only 22 m above mean sea level. The closest land is lonely Ushakov Island 140 km further north, Vize Island lies at the northern end of the Kara Sea, roughly midway between Franz Josef Land and Severnaya Zemlya. It belongs to the Taymyrsky Dolgano-Nenetsky District of the Krasnoyarsk Krai administrative division of Russia, owing to its extreme northerly location, the surrounding sea is covered with pack ice in the winter, and it is quite full of ice floes even in the summer. In 1924, oceanographer Vladimir Wiese studied the drift of Georgy Brusilovs ill-fated Russian ship Svyataya Anna when she was trapped on the ice of the Kara Sea. Vize detected an odd deviation of the path of the ships drift caused by variations of the patterns of sea. The data of the drift had been supplied by navigator Valerian Albanov, finally, the island was discovered on 13 August 1930 by a Soviet expedition led by Otto Schmidt aboard the Icebreaker Sedov under Captain Vladimir Voronin. The island was named after Professor Vize of the Soviet Arctic Institute who was at the time aboard the Sedov, the first wintering in Vize Island took place in 1945–46. A hydrometeorological polar station was established on 1 November 1945, Vize Islands polar station is one of the northernmost in the world. List of islands of Russia List of research stations in the Arctic Summary of the Arctic archipelagos, scott Polar Research Institute, University of Cambridge. Arctic Postal History - Picture of a radiogram from airplane H425 to the base at Vize Island
44.
Melt pond
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Melt ponds are pools of open water that form on sea ice in the warmer months of spring and summer. The ponds are found on glacial ice and ice shelfs. Ponds of melted water can develop under the ice. Melt ponds are usually darker than the ice, and their distribution. They absorb solar radiation rather than reflecting it as ice does and and this differential, which had not been scientifically investigated until recently, has a large effect on the rate of ice melting and the extent of ice cover. Melt ponds can melt through to the oceans surface, seawater entering the pond increases the melt rate because the salty water of the ocean is warmer than the fresh water of the pond. The increase in salinity also depresses the waters freezing point, water from melt ponds over land surface can run into crevasses or moulins – tubes leading under ice sheets or glaciers – turning into meltwater. The water may reach the underlying rock, the effect is an increase in the rate of ice flow to the oceans, as the fluid behaves like a lubricant in the basal sliding of glaciers. The effects of melt ponds are diverse, seasonal melt ponded and penetrating under glaciers shows seasonal acceleration and deceleration of ice flows affecting whole icesheets. Ponding in the extreme is lakes and lakes in association with glaciers are examined in the case of the Missoula Floods. Moulin Glacier ice accumulation Antarctic ice pack Arctic ice pack
45.
Albedo
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Albedo is a measure for reflectance or optical brightness. It is dimensionless and measured on a scale from zero to one, surface albedo is defined as the ratio of radiation reflected to the radiation incident on a surface. The proportion reflected is not only determined by properties of the surface itself and these factors vary with atmospheric composition, geographic location and time. While bi-hemispherical reflectance is calculated for an angle of incidence. The temporal resolution may range from seconds to daily, seasonal or annual averages, unless given for a specific wavelength, albedo refers to the entire spectrum of solar radiation. Due to measurement constraints, it is given for the spectrum in which most solar energy reaches the surface. This spectrum includes visible light, which explains why surfaces with a low albedo appear dark, albedo is an important concept in climatology, astronomy, and environmental management. The term albedo was introduced into optics by Johann Heinrich Lambert in his 1760 work Photometria, any albedo in visible light falls within a range of about 0.9 for fresh snow to about 0.04 for charcoal, one of the darkest substances. Deeply shadowed cavities can achieve an effective albedo approaching the zero of a black body, when seen from a distance, the ocean surface has a low albedo, as do most forests, whereas desert areas have some of the highest albedos among landforms. Most land areas are in a range of 0.1 to 0.4. The average albedo of Earth is about 0.3 and this is far higher than for the ocean primarily because of the contribution of clouds. Earths surface albedo is regularly estimated via Earth observation satellite sensors such as NASAs MODIS instruments on board the Terra, thereby, the BRDF allows to translate observations of reflectance into albedo. Earths average surface temperature due to its albedo and the effect is currently about 15 °C. If Earth were frozen entirely, the temperature of the planet would drop below −40 °C. If only the land masses became covered by glaciers, the mean temperature of the planet would drop to about 0 °C. In contrast, if the entire Earth was covered by water — a so-called aquaplanet — the average temperature on the planet would rise to almost 27 °C, hence, the actual albedo α can then be given as, α = α ¯ + D α ¯ ¯. Directional-hemispherical reflectance is sometimes referred to as black-sky albedo and bi-hemispherical reflectance as white-sky albedo and these terms are important because they allow the albedo to be calculated for any given illumination conditions from a knowledge of the intrinsic properties of the surface. The albedos of planets, satellites and asteroids can be used to infer much about their properties, the study of albedos, their dependence on wavelength, lighting angle, and variation in time comprises a major part of the astronomical field of photometry
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Topography
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Topography is the study of the shape and features of the surface of the Earth and other observable astronomical objects including planets, moons, and asteroids. The topography of an area could refer to the shapes and features themselves. This field of geoscience and planetary science is concerned with detail in general, including not only relief but also natural and artificial features. This meaning is common in the United States, where topographic maps with elevation contours have made topography synonymous with relief. The older sense of topography as the study of place still has currency in Europe, topography in a narrow sense involves the recording of relief or terrain, the three-dimensional quality of the surface, and the identification of specific landforms. This is also known as geomorphometry, in modern usage, this involves generation of elevation data in digital form. It is often considered to include the representation of the landform on a map by a variety of techniques, including contour lines, hypsometric tints. The term topography originated in ancient Greece and continued in ancient Rome, the word comes from the Greek τόπος and -γραφία. In classical literature this refers to writing about a place or places, in Britain and in Europe in general, the word topography is still sometimes used in its original sense. Detailed military surveys in Britain were called Ordnance Surveys, and this term was used into the 20th century as generic for topographic surveys, the earliest scientific surveys in France were called the Cassini maps after the family who produced them over four generations. The term topographic surveys appears to be American in origin, the earliest detailed surveys in the United States were made by the “Topographical Bureau of the Army, ” formed during the War of 1812, which became the Corps of Topographical Engineers in 1838. In the 20th century, the term started to be used to describe surface description in other fields where mapping in a broader sense is used. An objective of topography is to determine the position of any feature or more generally any point in terms of both a horizontal coordinate system such as latitude, longitude, and altitude, identifying features, and recognizing typical landform patterns are also part of the field. There are a variety of approaches to studying topography, which method to use depend on the scale and size of the area under study, its accessibility, and the quality of existing surveys. Work on one of the first topographic maps was begun in France by Giovanni Domenico Cassini, in areas where there has been an extensive direct survey and mapping program, the compiled data forms the basis of basic digital elevation datasets such as USGS DEM data. This data must often be cleaned to eliminate discrepancies between surveys, but it forms a valuable set of information for large-scale analysis. The original American topographic surveys involved not only recording of relief, remote sensing is a general term for geodata collection at a distance from the subject area. Besides their role in photogrammetry, aerial and satellite imagery can be used to identify and delineate terrain features, certainly they have become more and more a part of geovisualization, whether maps or GIS systems
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Measurement of sea ice
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Measurement of sea ice is important for safety of navigation and for monitoring the environment, particularly the climate. Sea ice extent interacts with large patterns such as the North Atlantic oscillation and Atlantic Multidecadal Oscillation. The amount of sea ice coverage in the arctic has been of interest for centuries, as the Northwest Passage was of high interest for trade, modern direct records include data about ice extent, ice area, concentration, thickness, and the age of the ice. The current trends in the show a significant decline in Northern hemisphere sea ice. The arctic sea ice is a dynamic climate-system component and is linked to the Atlantic multidecadal variability, there are circular changes of sea ice patterns but so far no clear patterns based on modeling predictions. Records assembled by Vikings showing the number of weeks per year that ice occurred along the north coast of Iceland date back to A. D.870, more extensive written records of Arctic sea ice date back to the mid-18th century. The earliest of those records relate to Northern Hemisphere shipping lanes, air temperature records dating back to the 1880s can serve as a stand-in for Arctic sea ice, but such temperature records were initially collected at only 11 locations. Russia’s Arctic and Antarctic Research Institute has compiled ice charts dating back to 1933, in the Antarctic, direct data prior to the satellite record are even more sparse. To try to extend the record of Southern Hemisphere sea ice extent further back in time. One is records kept by Antarctic whalers that document the location of all whales caught, because whales tend to congregate near the sea ice edge to feed, their locations could be a proxy for the ice extent. Other proxies use the presence of phytoplankton-derived organic compounds and other extremophiles traces in Antarctic ice cores, there are further extensive sets of multicentury historical records of arctic and subarctic sea ice and uses, among others high-resolution paleo proxy sea-ice records. Useful satellite data concerning sea ice began in December 1972 with the Electrically Scanning Microwave Radiometer instrument, however, this was not directly comparable with the later SMMR/SSMI, and so the practical record begins in late 1978 with the launch of NASA’s Scanning Multichannel Microwave Radiometer satellite. And continues with the Special Sensor Microwave/Imager, advanced Microwave Scanning Radiometer and Cryosat-2. Since 1979, satellites have provided a consistent continuous record of sea ice, satellite images of sea ice are made from observations of microwave energy radiated from the Earth’s surface. Because ocean water emits microwaves differently from sea ice, ice looks different from water to the satellite sensor—see sea ice emissivity modelling, the observations are processed into digital picture elements, or pixels. Each pixel represents a square surface area on Earth, the first instruments provided approximately 25 kilometers by 25 kilometers resolution, later instruments higher. Algorithms examine the microwave emissions, and their vertical and horizontal polarisations, Sea ice may be considered in terms of total volume, or in terms of areal coverage. There are two ways to express the total ice cover, ice area and ice extent
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