1.
Sea ice
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Sea ice arises as seawater freezes. Because ice is less dense water, it floats on the oceans surface. Sea ice covers about 7% of the Earth’s surface and about 12% of the world’s oceans. Much of the sea ice is enclosed within the polar ice packs in the Earths polar regions, the Arctic ice pack of the Arctic Ocean. Polar packs undergo a significant yearly cycling in surface extent, a natural process upon which depends the Arctic ecology, due to the action of winds, currents and temperature fluctuations, sea ice is very dynamic, leading to a wide variety of ice types and features. Sea ice may be contrasted with icebergs, which are chunks of ice shelves or glaciers that calve into the ocean, depending on location, sea ice expanses may also incorporate icebergs. Sea ice does not simply grow and melt, during its lifespan, it is very dynamic. Due to the action of winds, currents, water temperature. Sea ice is classified according to whether or not it is able to drift, Sea ice can be classified according to whether or not it is attached to the shoreline. If attached, it is called landfast ice, or more often, alternatively, and unlike fast ice, drift ice occurs further offshore in very wide areas, and encompasses ice that is free to move with currents and winds. The physical boundary between fast ice and drift ice is the fast ice boundary, the drift ice zone may be further divided into a shear zone, a marginal ice zone and a central pack. Drift ice consists of floes, individual pieces of sea ice 20 metres or more across, the term pack ice is used either as a synonym to drift ice, or to designate drift ice zone in which the floes are densely packed. The overall sea ice cover is termed the ice canopy from the perspective of submarine navigation, another classification used by scientists to describe sea ice is based on age, that is, on its development stages. These stages are, new ice, nilas, young ice, first-year, new ice is a general term used for recently frozen sea water that does not yet make up solid ice. It may consist of ice, slush, or shuga. Other terms, such as ice and pancake ice, are used for ice crystal accumulations under the action of wind. Nilas designates a sea ice crust up to 10 centimetres in thickness and it bends without breaking around waves and swells. Nilas can be subdivided into dark nilas – up to 5 centimetres in thickness and very dark
2.
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
3.
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
4.
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
5.
Theodolite
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A theodolite /θiːˈɒdəlaɪt/ is a precision instrument for measuring angles in the horizontal and vertical planes. Theodolites are used mainly for surveying applications, and have adapted for specialized purposes such as meteorology. A modern theodolite consists of a telescope mounted within two perpendicular axes, the horizontal or trunnion axis and the zenith axis. A theodolite measures vertical angles as angles between the zenith, forwards or plunged—typically approximately 90 and 270 degrees, when the telescope is pointed at a target object, the angle of each of these axes can be measured with great precision, typically to seconds of arc. A theodolite may be either transit or non-transit, in a transit theodolite, the telescope can be inverted in the vertical plane, whereas the rotation in the same plane is restricted to a semi-circle in a non-transit theodolite. Some types of transit theodolites do not allow the measurement of vertical angles, the builders level is sometimes mistaken for a transit theodolite, but it measures neither horizontal nor vertical angles. It uses a level to set a telescope level to define a line of sight along a horizontal plane. A theodolite is mounted on its head by means of a forced centering plate or tribrach containing four thumbscrews, or in modern theodolites. Before use, a theodolite must be placed vertically above the point to be measured using a plumb bob. The instrument is then set level using leveling footscrews and circular, both axes of a theodolite are equipped with graduated circles that can be read through magnifying lenses. The vertical circle which transits about the horizontal axis should read 90° when the axis is horizontal, or 270° when the instrument is in its second position. Half of the difference between the two positions is called the index error, the horizontal and vertical axes of a theodolite must be perpendicular, if not then a horizontal axis error exists. This can be tested by aligning the tubular spirit bubble parallel to a line between two footscrews and setting the bubble central, a horizontal axis error is present if the bubble runs off central when the tubular spirit bubble is reversed. To adjust, the operator removes 1/2 the amount the bubble has run off using the screw, then re-level, test. If not, then a collimation error exists, index error, horizontal axis error and collimation error are regularly determined by calibration and are removed by mechanical adjustment. Their existence is taken account in the choice of measurement procedure in order to eliminate their effect on the measurement results of the theodolite. The term diopter was used in old texts as a synonym for theodolite. This derives from an astronomical instrument called a dioptra
6.
Differential GPS
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DGPS uses a network of fixed, ground-based reference stations to broadcast the difference between the positions indicated by the GPS satellite systems and the known fixed positions. These stations broadcast the difference between the measured satellite pseudoranges and actual pseudoranges, and receiver stations may correct their pseudoranges by the same amount, the digital correction signal is typically broadcast locally over ground-based transmitters of shorter range. The term refers to a technique of augmentation. The United States Coast Guard and Canadian Coast Guard each run such systems in the U. S. the USCGs DGPS system has been named NDGPS and is now jointly administered by the Coast Guard and the U. S. Department of Transportation’s Federal Highway Administration. It consists of broadcast sites located throughout the inland and coastal portions of the United States including Alaska, Hawaii, a similar system that transmits corrections from orbiting satellites instead of ground-based transmitters is called a Wide-Area DGPS or Satellite Based Augmentation System. When GPS was first being put into service, the US military was concerned about the possibility of enemy forces using the globally available GPS signals to guide their own weapon systems. Originally, the government thought the coarse acquisition signal would only give about 100 meter accuracy, but with improved receiver designs and this technique, known as Selective Availability, or SA for short, seriously degraded the usefulness of the GPS signal for non-military users. This presented a problem for users who relied upon ground-based radio navigation systems such as LORAN, VOR. The advent of a global satellite system could provide greatly improved accuracy. The accuracy inherent in the S/A signal was too poor to make this realistic. Through the early to mid 1980s, a number of developed a solution to the SA problem. This suggested that broadcasting this offset to local GPS receivers could eliminate the effects of SA, resulting in closer to GPSs theoretical performance. Additionally, another source of errors in a GPS fix is due to transmission delays in the ionosphere. This offered an improvement to about 5 meters accuracy, more than enough for most civilian needs, the US Coast Guard was one of the more aggressive proponents of the DGPS system, experimenting with the system on an ever-wider basis through the late 1980s and early 1990s. These signals are broadcast on marine longwave frequencies, which could be received on existing radiotelephones, almost all major GPS vendors offered units with DGPS inputs, not only for the USCG signals, but also aviation units on either VHF or commercial AM radio bands. Plans were put into place to expand the system across the US, the quality of the DGPS corrections generally fell with distance, and large transmitters capable of covering large areas tend to cluster near cities. This meant that lower-population areas, notably in the midwest and Alaska, in addition the system provides single or dual coverage to a majority of the inland portion of United States. Instead, the FAA started studying broadcasting the signals across the entire hemisphere from communications satellites in geostationary orbit and this led to the Wide Area Augmentation System and similar systems, although these are generally not referred to as DGPS, or alternatively, wide-area DGPS
7.
Scuba diving
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Scuba diving is a mode of underwater diving in which the scuba diver uses a self-contained underwater breathing apparatus which is completely independent of surface supply, to breathe underwater. They may include additional cylinders for decompression gas or emergency breathing gas, closed-circuit or semi-closed circuit rebreather scuba systems allow recycling of exhaled gases. The volume of gas used is reduced compared to that of open circuit, therefore, scuba divers engaged in armed forces covert operations may be referred to as frogmen, combat divers or attack swimmers. A scuba diver primarily moves underwater by using fins attached to the feet, scuba divers are trained in the procedures and skills appropriate to their level of certification by instructors affiliated to the diver certification organisations which issue these certifications. A minimum level of fitness and health is required by most training organisations, the closed-circuit rebreathers were first developed for escape and rescue purposes, and were modified for military use, due to their stealth advantages, as they produce very few bubbles. The first commercially successful closed-circuit scuba was designed and built by English diving engineer, Henry Fleuss in 1878, while working for Siebe Gorman in London. Sir Robert Davis, head of Siebe Gorman, improved the oxygen rebreather in 1910 with his invention of the Davis Submerged Escape Apparatus, rebreathers have been increasingly used by civilians for recreation, especially since the end of the Cold War. This reduced the risk of attack by Communist Bloc forces. After that, the armed forces had less reason to requisition civilian rebreather patents. The single hose two stage scuba regulators trace their origins to Australia, where Ted Eldred developed the first example of type of regulator. This was developed because patents protected the Aqualungs twin hose design, the single hose regulator separates the demand valve from the cylinder, giving the diver air at the ambient pressure at the mouth, rather than ambient pressure at the cylinder valve. The term SCUBA originally referred to United States combat frogmens oxygen rebreathers, SCUBA was originally an acronym, but is now generally used as a common noun or adjective, scuba. It has become acceptable to refer to equipment or scuba apparatus—examples of the linguistic RAS syndrome. Scuba diving may be performed for a number of reasons, both personal and professional, recreational diving is done purely for enjoyment and has a number of technical disciplines to increase interest underwater, such as cave diving, wreck diving, ice diving and deep diving. Divers may be employed professionally to perform tasks underwater, some of these tasks are suitable for scuba. There are divers who work, full or part-time, in the diving community as instructors, assistant instructors, divemasters. Other specialist areas of diving include military diving, with a long history of military frogmen in various roles. Their roles include direct combat, infiltration behind enemy lines, placing mines or using a manned torpedo, in some cases diver rescue teams may also be part of a fire department, paramedical service or lifeguard unit, and may be classed as public service diving
8.
Thermistor
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A thermistor is a type of resistor whose resistance is dependent on temperature, more so than in standard resistors. The word is a portmanteau of thermal and resistor, thermistors are widely used as inrush current limiter, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements. Thermistors are of two fundamental types, With NTC, resistance decreases as temperature rises to protect against inrush overvoltage conditions. Commonly installed in parallel as a current sink, with PTC, resistance increases as temperature rises to protect against overcurrent conditions. Commonly installed in series as a resettable fuse, thermistors differ from resistance temperature detectors in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. If k is positive, the resistance increases with increasing temperature, if k is negative, the resistance decreases with increasing temperature, and the device is called a negative temperature coefficient thermistor. Resistors that are not thermistors are designed to have a k as close to 0 as possible, instead of the temperature coefficient k, sometimes the temperature coefficient of resistance α T is used. It is defined as α T =1 R d R d T and this α T coefficient should not be confused with the a parameter below. In practice, the linear approximation works only over a temperature range. For accurate temperature measurements, the curve of the device must be described in more detail. The Steinhart–Hart equation is a widely used third-order approximation,1 T = a + b ln + c 3 where a, b and c are called the Steinhart–Hart parameters, T is the absolute temperature and R is the resistance. As an example, typical values for a thermistor with a resistance of 3 kΩ at room temperature are, a =1.40 ×10 −3 b =2.37 ×10 −4 c =9. Solving for R yields, R = R0 e − B or, alternatively and this can be solved for the temperature, T = B ln The B-parameter equation can also be written as ln R = B / T + ln r ∞. This can be used to convert the function of resistance vs. temperature of a thermistor into a function of ln R vs.1 / T. The average slope of this function will yield an estimate of the value of the B parameter. Many NTC thermistors are made from a disc, rod, plate. They work because raising the temperature of a semiconductor increases the number of charge carriers - it promotes them into the conduction band. The more charge carriers that are available, the current a material can conduct
9.
Electromagnetic induction
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Electromagnetic or magnetic induction is the production of an electromotive force across an electrical conductor due to its dynamic interaction with a magnetic field. Michael Faraday is generally credited with the discovery of induction in 1831, Lenzs law describes the direction of the induced field. Faradays law was later generalized to become the Maxwell-Faraday equation, one of the four Maxwells equations in James Clerk Maxwells theory of electromagnetism, electromagnetic induction has found many applications in technology, including electrical components such as inductors and transformers, and devices such as electric motors and generators. Electromagnetic induction was first discovered by Michael Faraday, who made his discovery public in 1831 and it was discovered independently by Joseph Henry in 1832. In Faradays first experimental demonstration, he wrapped two wires around opposite sides of a ring or torus. He plugged one wire into a galvanometer, and watched it as he connected the wire to a battery. He saw a transient current, which he called a wave of electricity and this induction was due to the change in magnetic flux that occurred when the battery was connected and disconnected. Within two months, Faraday found several other manifestations of electromagnetic induction, Faraday explained electromagnetic induction using a concept he called lines of force. However, scientists at the time widely rejected his theoretical ideas, an exception was James Clerk Maxwell, who used Faradays ideas as the basis of his quantitative electromagnetic theory. Heavisides version is the form recognized today in the group of known as Maxwells equations. In 1834 Heinrich Lenz formulated the law named after him to describe the flux through the circuit, Lenzs law gives the direction of the induced EMF and current resulting from electromagnetic induction. Faradays law of induction makes use of the magnetic flux ΦB through a region of space enclosed by a wire loop. The magnetic flux is defined by an integral, Φ B = ∫ Σ B ⋅ d A. The dot product B·dA corresponds to an amount of magnetic flux. In more visual terms, the flux through the wire loop is proportional to the number of magnetic flux lines that pass through the loop. When the flux through the changes, Faradays law of induction says that the wire loop acquires an electromotive force. The direction of the force is given by Lenzs law which states that an induced current will flow in the direction that will oppose the change which produced it. This is due to the sign in the previous equation
10.
Submarine pipeline
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A submarine pipeline is a pipeline that is laid on the seabed or below it inside a trench. In some cases, the pipeline is mostly on-land but in places it crosses water expanses, such as seas, straights. Submarine pipelines are used primarily to oil or gas. A distinction is made between a flowline and a pipeline. The former is a pipeline, in the sense that it is used to connect subsea wellheads, manifolds. The latter, sometimes referred to as a pipeline, is used to bring the resource to shore. One of the earliest and most critical tasks in a submarine pipeline planning exercise is the route selection, the primary physical factor to be considered in submarine pipeline construction is the state of the seabed – whether it is smooth or uneven. If it is uneven, the pipeline will include free spans when it connects two points, leaving the section in between unsupported. If an unsupported section is too long, the stress exerted onto it may be excessive. Vibration from current-induced vortexes may also become an issue, corrective measures for unsupported pipeline spans include seabed leveling and post-installation support, such as berm or sand infilling below the pipeline. The strength of the seabed is another significant parameter, if the soil is not strong enough, the pipeline may sink into it to an extent where inspection, maintenance procedures and prospective tie-ins become difficult to carry out. At the other extreme, a rocky seabed is expensive to trench and, at points, abrasion. Ideally, the soil should be such as to allow the pipe to settle into it to some extent, the evolution of these features is difficult to predict so it is preferable to avoid the areas where they are known to exist. Submarine landslides, They result from high rates and occur on steeper slopes. They can be triggered by earthquakes, currents, High currents are objectionable in that they hinder pipe laying operations. For instance, in shallow seas tidal currents may be strong in a strait between two islands. Under these circumstances, it may be preferable to bring the pipe elsewhere, waves, In shallow waters, waves can also be problematic for pipeline laying operations and, subsequently, to its stability, because of the waters scouring action. This is one of a number of reasons why landfalls are particularly delicate areas to plan, ice-related issues, In freezing waters, floating ice features often drift into shallower waters, and their keel comes into contact with the seabed
11.
Seabed gouging by ice
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Seabed gouging by ice is a process that occurs when floating ice features drift into shallower areas and their keel comes into contact with the seabed. As they keep drifting, they produce long, narrow furrows most often called gouges and this phenomenon is common in offshore environments where ice is known to exist. Although it also occurs in rivers and lakes, it appears to be documented from oceans. Seabed scours produced via this mechanism should not be confused with strudel scours and these result from spring run-off water flowing onto the surface of a given sea ice expanse, which eventually drains away through cracks, seal breathing holes, etc. The resulting turbulence is strong enough to carve a depression into the seabed and it appears Charles Darwin speculated in 1855 about the possibility that icebergs could gouge the seabed as they drifted across isobaths. Some discussion on the involvement of sea ice was brought up in the 1920s, at that time, ship-borne sidescan sonar surveys in the Canadian Beaufort Sea began to gather actual evidence of this mechanism. Seabed gouges were subsequently observed further north, in the Canadian Arctic Archipelago, throughout that decade, seabed gouging by ice was investigated extensively. Since then, means of protecting these structures against ice action became an important concern, an oil spill in this environment would be problematic in terms of detection and clean-up. Scientists in fields of other than offshore engineering have also addressed seabed gouging. However, much of it appears to have been documented from an engineering perspective. Seabed gouging by ice is an eminently discreet phenomenon, little sign of it can be observed from above the water surface – the odd evidence includes sea floor sediments incorporated into the ice, information of interest on these gouges includes, depth, width, length and orientation. Gouging frequency – the number of gouges produced at a given location per unit time – is another important parameter, repetitive mapping involves repeating these surveys a number of times, at an interval ranging from a few to several years, as a means of estimating gouging frequency. Seabed gouges produced by drifting ice features can be many kilometers in length, in Northern Canada and Alaska, gouge depths may reach 5 metres. Most, however, do not exceed 1 meter, anything deeper than 2 meters is referred to by the offshore engineering community as an extreme event. Gouge widths range from a few meters to a few hundred meters, the maximum water depths at which gouges have been reported range from 450 to 850 metres, northwest of Svalbard in the Arctic Ocean. These are thought to be remnant traces left by icebergs during the Pleistocene, thousands of years ago, when the sea level was lower than what it is today. In the Beaufort Sea, Northern Canada, a 50 km long gouge was shown to exist, with a depth of 8.5 metres. The gouge is not always straight but varies in orientation and this event is thought to be about 2000 years old
12.
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
13.
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
14.
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
15.
Cryovolcano
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A cryovolcano is a theoretical type of volcano that erupts volatiles such as water, ammonia or methane, instead of molten rock. Collectively referred to as cryomagma or ice-volcanic melt, these substances are usually liquids and can form plumes, after eruption, cryomagma is expected to condense to a solid form when exposed to the very low surrounding temperature. Cryovolcanoes may potentially form on icy moons and other objects with abundant water past the Solar Systems snow line, a number of features have been identified as possible cryovolcanoes on Pluto, Titan and Ceres. In addition, although they are not known to form volcanoes, ice geysers have been observed on Enceladus, one potential energy source on some solar system bodies for melting ices and producing cryovolcanoes is tidal friction. It has also suggested that translucent deposits of frozen materials could create a subsurface greenhouse effect that would accumulate the required heat. Signs of past warming of the Kuiper belt object Quaoar have led scientists to speculate that it exhibited cryovolcanism in the past, on November 27,2005, Cassini photographed geysers on the south pole of Enceladus. Indirect evidence of activity was later observed on several other icy moons of the Solar System, including Europa, Titan, Ganymede. Cryovolcanism is one process hypothesized to be a significant source of the found in Titans atmosphere. Subsequent observations by New Horizons in 2015 found that Charon has a youthful surface, Pluto itself has two features that have been identified as possible cryovolcanoes, being mountains with indented peaks. In 2015, two bright spots inside a crater of the dwarf planet Ceres were imaged by the Dawn spacecraft. In September 2016, NASA JPL and NASA Goddard scientists released findings that large Ahuna Dome on Ceres is a volcanic dome unlike any seen elsewhere in the solar system, mountain is likely volcanic in nature. Specifically, it would be a cryovolcano -- a volcano that erupts a liquid made of such as water. The only known example of a cryovolcano that potentially formed from a salty mud mix, in addition, at least some of Ceres well known bright spots are likely also cryovolcanic in origin. A study published in March 2017 suggests that Occators most recent large eruption occurred about 4 million years ago, Triton - Triton at the eight Planets South Pole of Triton - Triton at SolarViews. Ice volcanoes are all the rage this winter, How do you stimulate a regional tourist economy, ice volcanoes attract curious explorers to Lake Michigan shore, Experts warn to explore formations with caution
16.
Offshore geotechnical engineering
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Offshore geotechnical engineering is a sub-field of geotechnical engineering. It is concerned with design, construction, maintenance and decommissioning for human-made structures in the sea. Oil platforms, artificial islands and submarine pipelines are examples of such structures, the seabed has to be able to withstand the weight of these structures and the applied loads. Geohazards must also be taken into account, today, there are more than 7,000 offshore platforms operating at a water depth up to and exceeding 2000 m. An offshore environment has several implications for geotechnical engineering and these include the following, Ground improvement and site investigation are expensive. Offshore structures are tall, often extending over 100 metres above their foundation, offshore structures typically have to contend with significant lateral loads. Cyclic loading can be a design issue. Offshore structures are exposed to a range of geohazards. The codes and technical standards are different from those used for onshore developments, design focuses on ultimate limit state as opposed to deformation. Design modifications during construction are either unfeasible or very expensive, the design life of these structures often ranges between 25–50 years. The environmental and financial costs in case of failure can be higher, offshore structures are exposed to various environmental loads, wind, waves, currents and, in cold oceans, sea ice and icebergs. Environmental loads act primarily in the direction, but also have a vertical component. Some of these loads get transmitted to the foundation, wind, wave and current regimes can be estimated from meteorological and oceanographic data, which are collectively referred to as metocean data. Earthquake-induced loading can also occur – they proceed in the opposite direction, depending on location, other geohazards may also be an issue. All of these phenomena may affect the integrity or the serviceability of the structure, marine sediments are composed of detrital material as well as remains of marine organisms, the latter making up calcareous soils. Total sediment thickness varies on a regional scale – it is higher near the coastline than it is away from it. In places, the seabed can be devoid of sediment, due to strong bottom currents, the consolidation state of the soil is either normally consolidated, overconsolidated or underconsolidated. Wave forces induce motion of floating structures in all six degrees of freedom – they are a design criterion for offshore structures
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