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An iceberg is a large piece of ice from freshwater that has broken off from a snow-formed glacier or ice shelf and is floating in open water.[1] It may subsequently become frozen into pack ice. Alternatively, it may come to rest on the seabed in shallower water, causing ice scour (also known as ice gouging) or becoming an ice island.
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The word "iceberg" is a partial loan translation from Dutch ijsberg, literally meaning ice mountain,[2] cognate to Danish Isbjerg, German Eisberg, Low Saxon Iesbarg and Swedish/Norwegian Isberg.
Because the density of pure ice is about 920 kg/m³, and that of sea water about 1025 kg/m³, typically only one-tenth of the volume of an iceberg is above water. The shape of the underwater portion can be difficult to judge by looking at the portion above the surface. 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 (3–250 ft) above sea level and weigh 100,000 to 200 000 tons. The tallest known iceberg in the North Atlantic was 168 metres (550 ft) above sea level, making it the height of a 55-storey building. Despite their size, the icebergs of Newfoundland move an average of 17 kilometres a day (10 mi).[3] These icebergs originate from the glaciers of western Greenland, and may have an interior temperature of -15 to -20°C (5 to -4 °F).[4]
Though 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 km long and 37 km wide (183-23 mi), with a surface area of 11,000 km² (4,250 mi²). The mass was estimated around three billion tonnes.
When an iceberg melts, it makes a fizzing sound called "Bergie Seltzer"". This sound is made when compressed air bubbles trapped in the iceberg pop. The bubbles come from air trapped in snow layers that later became glacial ice.[4]
Ice campers who camp on top of flat or hollowed icebergs are known as icebergers.
Names for various sizes of iceberg are not universal, but usually follow a similar pattern. The size classification in the table below is used by the International Ice Patrol:[5]
| Size Category | Height | Length |
|---|---|---|
| Growler | Less than 1 metre (3.3 ft) | Less than 5 metres (16 ft) |
| Bergy Bit | 1–5 metres (3.3–16 ft) | 5–15 metres (16–49 ft) |
| Small | 5–15 metres (16–49 ft) | 15–60 metres (49–197 ft) |
| Medium | 15–45 metres (49–148 ft) | 60–120 metres (200–390 ft) |
| Large | 45–75 metres (148–246 ft) | 120–200 metres (390–660 ft) |
| Very Large | Over 75 metres (246 ft) | Over 200 metres (660 ft) |
In addition to the above size classification, there is also a type of classification based on shape. The two basic types of iceberg forms are tabular and non-tabular.
Tabular icebergs have steep sides and a flat top, much like a plateau, with a length-to-height ratio of more than 5:1.[6] This type of iceberg can be quite large, as in the case of Pobeda Ice Island.
Non-tabular icebergs have different shapes, and include:[7]
Icebergs are monitored worldwide by the U.S. National Ice Center (NIC), established in 1995, which produces analyses and forecasts of Arctic, Antarctic, Great Lakes and Chesapeake Bay ice conditions. More than 95% of the data used in its sea ice analyses are derived from the remote sensors on polar-orbiting satellites that survey these remote regions of the Earth.
The NIC is the only organization that names and tracks all Antarctic Icebergs. It assigns each iceberg larger than 10 nautical miles (18 km) along at least one axis a name composed of a letter indicating its point of origin and a running number. The letters used are as follows:
Iceberg B15, which calved from the Ross Ice Shelf in 2000 and initially had an area of 11,000 km², was the largest iceberg ever recorded. It broke apart in November 2002. The largest remaining piece of it, Iceberg B-15A, with an area of 3,000 km², was still the largest iceberg on Earth until it ran aground and split into several pieces October 27, 2005. It has been determined that the cause of the breakup was an ocean swell generated by an Alaskan storm 6 days earlier and 13,500 km (8,370 miles) away.[8]
In the 20th century, several scientific bodies were established to study and monitor the icebergs. The International Ice Patrol, formed in 1914 in response to the Titanic disaster, monitors iceberg dangers near the Grand Banks of Newfoundland and provide the "limits of all known ice" in that vicinity to the maritime community.
In March 2008, a chunk of Antarctic ice, about seven times the size of Manhattan, suddenly collapsed, putting an even greater portion of glacial ice at risk, and an ice shelf about the size of Connecticut was "hanging by a thread" as of March 25, 2008.[9][10]
There was no system in place before April 1912 to track icebergs, to guard against ship collisions. The sinking of the RMS Titanic, which caused the deaths of 1,523 of its 2,228 passengers, created the demand for a system to observe icebergs. For the remainder of the ice season of that year, the United States Navy patrolled the waters and monitored ice flow. In November 1913, the International Conference on the Safety of Life at Sea met in London to devise a more permanent system of observing icebergs. Within three months, the participating maritime nations had formed the International Ice Patrol (IIP). The goal of the IIP was to collect data on meteorology and oceanography in order to measure currents, iceflow, ocean temperature, and salinity levels. They published their first records in 1921, which allowed for a year-by-year comparison of iceberg movement.
New technologies monitor icebergs. Aerial surveillance of the seas in the early 1930s allowed for the development of charter systems that could accurately detail the ocean currents and iceberg locations. In 1945, experiments tested the effectiveness of radar in detecting icebergs. A decade later, oceanographic monitoring outposts were established for the purpose of collecting data; these outposts continue to serve in environmental study. A computer was first installed on a ship for the purpose of oceanographic monitoring in 1964, which allowed for a faster evaluation of data. By the 1970s, icebreaking ships were equipped with automatic transmissions of satellite photographs of ice in Antarctica. Systems for optical satellites had been developed, but were still limited by weather conditions. In the 1980s, drifting buoys were used in Antarctic waters for oceanographic and climate research. They are equipped with sensors that measure ocean temperature and currents. Side-Looking Airborne Radar (SLAR) made it possible to acquire images regardless of weather conditions. On November 4, 1995, Canada launched RADARSAT-1. Developed by the Canadian Space Agency, it provides images of Earth for both scientific and commercial purposes. This system was the first to use Synthetic Aperture Radar (SAR), which sends microwave energy to the ocean surface and records the reflections to track icebergs. The European Space Agency launched ENVISAT on March 1, 2002, an environmental satellite which uses Advanced Synthetic Aperture Radar (ASAR). This can detect changes in surface height accurately. The Canadian Space Agency launched RADARSAT-2 in December 2007, which uses SAR and multipolarization modes and follows the same orbit path as RADARSAT-1.[11]
ICEBERG (from ice and Berg, Ger. for hill, mountain), a floating mass of ice broken from the end of a glacier or from an ice-sheet. The word is sometimes, but rarely, applied to the arch of an Arctic glacier viewed from the sea. It is more commonly used to describe huge floating masses of ice that drift from polar regions into navigable waters. They are occasionally encountered far beyond the polar regions, rising into beautiful forms with breakers roaring into their caves and streams of water pouring from their pinnacles in the warmer air. When, however, they rest in comparatively warm water, melting takes place most rapidly at the base and they frequently overturn. Only one-ninth of the mass of ice is seen above water. When a glacier descends to the sea, as in Alaska, and "advances into water, the depth of which approaches its thickness, the ends are broken off and the detached masses float away as icebergs. Many of the bergs are overturned, or at least tilted, as they set sail. If this does not happen at once it is likely to occur later as the result of the wave-cutting and melting which disturb their equilibrium" (T. C. Chamberlin and R. D. Salisbury, Geology: Processes and their Results, 1905). These bergs carry a load of debris from the glacier and gradually strew their load upon the sea floor. They do not travel far before losing all stony and earthy debris, but glacial material found in dredgings shows that icebergs occasionally carry their load far from land. The structure of the iceberg varies with its origin and is always that of the glacier or ice-sheet from which it was broken. The breaking off of the ice-sheet from a Greenland glacier is called locally the "calving" of the glacier. The constantly renewed material from which the icebergs are formed is brought down by the motion of the glacier. The ice-sheet cracks at the end, and masses break off, owing to the upward pressure of the water upon the lighter ice which is pushed into it. This is accomplished with considerable violence. The disintegration of an Arctic icesheet is a simpler matter, as the ice is already floating.
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Categories: I-IOL | Earth sciences
An Iceberg is a large piece of ice floating in the water. Icebergs are very dangerous to ships, and many ships have sunk after crashing into icebergs. The most famous one was RMS Titanic in 1912.
About 90% of an iceberg is below the water line and ten percent above. Just by looking at the part you can see, it is hard to tell how the part underwater looks, and how close you can get before crashing into it. Icebergs are dangerous for ships, especially during the months of April, May, and June.
The first person to give a correct scientific explanation of this phenomenon was Mikhail Lomonosov, around 1750: The density of ice is about 0.92 kg per liter, that of sea water is about 1.025 kg per liter. For this reason, 92 parts of the 1025, or about 90 percent of the iceberg's volume need to be below the water line. Lomonosov grew up on the shore of the White Sea in the Euorpean part of Russia. He studied in Marburg, and is credited with introducing the word iceberg into the Russian language.
Icebergs break off from larger structures made of ice, like glaciers or ice shelves. These are formed by snowfall in very cold places where it will not melt in the summer. The snow builds up and compacts into ice. This is gradually pulled downhill by gravity and into the sea. The ice then falls off and makes icebergs. The icebergs can drift in the sea for years before they have melted completely.
The biggest iceberg people know about was called B-15. It broke off from the Antarctic ice shelf in the year 2000, and was as large as the island of Jamaica (over 10,000km2). It soon started to break up into smaller pieces, some of which still remain in 2008.
   | Tracking Monsters - Satellite imagery to track arctic icebergs - Canadian Geographic Magazine In-depth |
| | Canadian Geographic Facts on Icebergs - Just the Facts - Icebergs - Canadian Geographic Magazine: In-depth |
| | Iceberg Physiology - Arctic iceberg physiology, habitat, behaviours, lifespan, range - Canadian Geographic Magazine In-depth |
| | iceberg - Online Etymology Dictionary |
| | Alaskan storm cracks giant iceberg to pieces in faraway Antarctica - Alaskan storm cracks giant iceberg to pieces in faraway Antarctica |
 | Iceberg Google maps - Iceberg - a vista de google |
| | Icebergs of The Arctic and Antarctic - Icebergs of The Arctic and Antarctic |
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