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Icebergs

Icebergs

An iceberg is a large mass of free-floating ice that has broken away from a glacier. Beautiful and dangerous, icebergs wander over the ocean surface until they melt. Most icebergs come from the glaciers of Greenland or from the massive ice sheets of Antarctica . A few icebergs originate from smaller Alaskan glaciers. Snow produces the glaciers and ice sheets so, ultimately, icebergs originate from snow. In contrast, "sea ice" originates from freezing salt water . When fragments break off of a glacier, icebergs are formed in a process called calving.

Icebergs consist of freshwater ice, pieces of debris, and trapped bubbles of air. The combination of ice and air bubbles causes sunlight shining on the icebergs to refract, coloring the ice spectacular shades of blue, green, and white. Color may also indicate age; blue icebergs are old, and green ones contain algae and are young. Icebergs come in a variety of shapes and sizes, some long and flat, others towering and massive.

An iceberg floats because it is lighter and less dense than salty seawater, but only a small part of the iceberg is visible above the surface of the sea. Typically, about 8090% of an iceberg is below sea level, so they drift with ocean currents rather than wind . Scientists who study icebergs classify true icebergs as pieces of ice that are greater than 16 ft (5 m) above sea level and wider than 98 ft (30 m) at the water line. Of course, icebergs may be much larger. Smaller pieces of floating ice are called "bergy bits" (3.316 ft or 15 m tall and 3398 ft or 1030 m wide) or "growlers" (less than 3.3 ft or 1 m tall and less than 33 ft or 10 m wide). The largest icebergs can be taller than 230 ft (70 m) and wider than 738 ft (225 m). Chunks of ice more massive than this are called ice islands. Ice islands are much more common in the Southern Hemisphere, where they break off the Antarctic ice sheets.

Because of the unusual forms they may take, icebergs are also classified by their shape. Flat icebergs are called tabular. Icebergs that are tall and flat are called blocky. Domed icebergs are shaped like a turtle shell, rounded, with gentle slopes. Drydock icebergs have been eroded by waves so that they are somewhat U-shaped. Perhaps the most spectacular are the pinnacle icebergs, which resemble mountain tops, with one or more central peaks reaching skyward.

The life span of an iceberg depends on its size but is typically about two years for icebergs in the Northern Hemisphere. Because they are larger, icebergs from Antarctica may last for several more years. Chief among the destructive forces that work against icebergs are wave action and heat. Wave action can break icebergs into smaller pieces and can cause icebergs to knock into each other and fracture. Relatively warm air and water temperature gradually melt the ice. Because icebergs float, they drift with water currents towards the equator into warmer water. Icebergs may drift as far as 8.5 mi (14 km) per day. Most icebergs have completely melted by the time they reach about 40 degrees latitude (north or south). There have been rare occasions when icebergs have drifted as far south as Bermuda (32 degrees north latitude), which is located about 900 mi (1,400 km) east of Charleston, South Carolina. In the Atlantic Ocean, they have also been found as far east as the Azores, islands in the Atlantic Ocean off the coast of Spain.

One of the best-known icebergs is the one that struck and sank the RMS Titanic on April 14, 1912, when the ship was on her maiden voyage. More than 1,500 people lost their lives in that disaster, which occurred near Newfoundland, Canada. As a result of the tragedy, the Coast Guard began monitoring icebergs to protect shipping interests in the North Atlantic sea lanes. Counts of icebergs drifting into the North Atlantic shipping lanes vary from year to year, with little predictability. During some years, no icebergs drift into the lanes; other years are marked by hundreds or moreas many as 1,572 have been counted in a single year. Many ships now carry their own radar equipment to detect icebergs. As recently as 1959, a Danish ship equipped with radar struck an iceberg and sank, resulting in 95 deaths. Some ships even rely on infrared sensors from airplanes and satellites. Sonar is also used to locate icebergs.

Modern iceberg research continues to focus on improving methods of tracking and monitoring icebergs, and on learning more about iceberg deterioration. In 1995, a huge iceberg broke free from the Larsen ice shelf in Antarctica. This iceberg was 48 mi (77 km) long, 23 mi (37 km) wide, and 600 ft (183 m) thick. The iceberg was approximately the size of the country of Luxembourg and isolated James Ross Island (one of Antarctica's islands) for the first time in recorded history. The megaberg was monitored by airplanes and satellites to make sure it didn't put ships at peril. According to some scientists, this highly unusual event could be evidence of global warming . Surges in the calving of icebergs known as Heinrich events are also known to be caused by irregular motions of Earth around the Sun that cause ocean waters of varying temperatures and salinity to change their circulation patterns. These cycles were common during the last glacial period, and glacial debris was carried by "iceberg armadas" to locations like Florida and the coast of Chile. Scientists have "captured" icebergs for study including crushing to measure their strength. It has been proposed to tow icebergs to drought-stricken regions of the world to solve water shortage problems; however, the cost and potential environmental impact of such an undertaking have so far discouraged any such attempts.

See also Glaciation; Ocean circulation and currents

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Iceberg

Iceberg

An iceberg is a large mass of free-floating ice that has broken away from a glacier. (Glaciers are flowing masses of ice, created by years of snowfall and cold temperatures.) Beautiful and dangerous, icebergs are carried about the ocean surface until they melt. Most icebergs come from the glaciers of Greenland or from the massive ice sheets of Antarctica.

The process of icebergs breaking off of a glacier is called calving. Icebergs consist of freshwater ice, pieces of debris, and trapped bubbles of air. The combination of ice and air bubbles causes sunlight shining on the icebergs to color the ice spectacular shades of blue, green, and white. Icebergs come in a variety of unusual shapes and sizes, some long and flat, others towering and massive.

An iceberg floats because it is lighter and less dense than the salty seawater, but only a small part of the iceberg is visible above sea level. Typically, about 80 to 90 percent of an iceberg is below sea level. Scientists who study icebergs classify true icebergs as pieces of ice that are higher than 16 feet (5 meters) above sea level and wider than 98 feet (30 meters) at the water line. The largest icebergs can be taller than 230 feet (70 meters) and wider than 738 feet (225 meters). Chunks of ice more massive than this are called ice islands. Ice islands are much more common in the Southern Hemisphere, where they break off from the Antarctic ice sheets.

The life span of an iceberg depends on its size, but is typically about two years in the Northern Hemisphere. Because they are larger, icebergs from Antarctica may last for several more years. The main destructive forces that work against icebergs are wave action and heat. Wave action can break icebergs into smaller pieces. It can also force icebergs to knock into each other, which can fracture them. Relatively warm air and water temperature gradually melt icebergs.

Words to Know

Calving: Process of iceberg formation in which a glacier flows into the sea and large chunks of glacial ice break free due to stress, pressure, or the forces of waves and tides.

Ice island: Thick slab of floating ice occupying an area as large as 180 square miles (460 square kilometers).

Ice sheet: Glacial ice that covers at least 19,500 square miles (50,000 square kilometers) of land and that flows in all directions, covering and obscuring the landscape below it.

Ice shelf: Section of an ice sheet that extends into the sea a considerable distance and that may be partially afloat.

Since icebergs float, they drift with water currents toward the warmer waters near the equator. Icebergs may drift as far as 8.5 miles (14 kilometers) per day. Most icebergs have completely melted by the time they reach about 40 degrees latitude, north and south. There have been rare occasions when icebergs have drifted as far south as the island of Bermuda in the Caribbean, and as far east as the Azores, islands in the Atlantic Ocean off the coast of Spain.

Loss of the Titanic to an iceberg

One of the best-known icebergs is the one that struck and sank the ocean liner Titanic on her maiden voyage in the spring of 1912. More than 1,500 people lost their lives in that disaster, which occurred near Newfoundland, Canada. As a result of the tragedy, 16 nations agreed to monitor icebergs to protect shipping interests in the North Atlantic sea lanes. Counts of icebergs drifting into the North Atlantic shipping lanes vary from year to year. Some years no icebergs drift into the lanes; other years are marked by hundreds or more. Many ships now carry their own radar equipment to detect icebergs. Some ships even rely on infrared sensors from airplanes and satellites. Sonar is also used to locate icebergs.

Modern iceberg research continues to focus on improving methods of tracking and monitoring icebergs and on learning more about iceberg deterioration. In 1995, a huge iceberg broke free from the Larsen Ice Shelf in Antarctica. Between the fall of 1998 and the spring of 1999, 662 square

miles (1,714 square kilometers) of area from the Larsen Ice Shelf calved away. In the fall of 2000, an iceberg measuring 30 by 11.5 miles (48 by 18.5 kilometers) calved from the Ross Ice Shelf in Antarctica. According to some scientists, these highly unusual events could be evidence of global warming.

Some people have proposed towing icebergs to regions of the world that suffer from drought. However, the cost and potential environmental impact of such a project have discouraged any such attempts.

[See also Glaciers ]

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iceberg

iceberg, mass of ice that has become detached, or calved, from the edge of an ice sheet or glacier and is floating on the ocean. Because ice is slightly less dense than water about one ninth of the total mass of a berg projects above the water. Greenland and other N Atlantic icebergs are usually peaked and irregular in shape; Antarctic icebergs are tabular, with flat tops and steep sides. Icebergs differ from other ocean ices: sea ice is formed directly from the freezing of ocean water; pack ice is tightly packed fragments of sea ice; ice floes are small, floating ice fragments that separate from pack ice; and fast ice is ice attached to a shore.

Greenland is the source of most of the icebergs in the N Atlantic, where the iceberg season lasts roughly from February to October. As a consequence of the loss of the Titanic through collision with an iceberg in 1912, a patrol of N Atlantic shipping channels was initiated in 1914 by the international agreement of 16 nations. Patrols use planes and surface vessels equipped with radar, loran, and underwater sound equipment. A constant census of bergs is maintained, and the location of an iceberg is reported to any ship in its vicinity.

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iceberg

ice·berg / ˈīsˌbərg/ • n. a large floating mass of ice detached from a glacier or ice sheet and carried out to sea. PHRASES: the tip of the iceberg the small, perceptible part of a much larger situation or problem that remains hidden: the statistics represent just the tip of the iceberg. ORIGIN: late 18th cent.: from Dutch ijsberg, from ijs ‘ice’ + berg ‘hill.’

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iceberg

iceberg Large drifting piece of ice, broken off from a glacier or polar ice-sheet. In the Northern Hemisphere, the main source of icebergs is the sw coast of Greenland. In the Southern Hemisphere, the glacial flow from Antarctica releases huge tabular icebergs. Icebergs can be dangerous to shipping, since only a small portion is visible above the surface of the water.

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iceberg

icebergBerg, burg, erg, exergue •Hamburg • Battenberg • Strasberg •Habsburg • Salzburg • Strasbourg •Pressburg • Spielberg • Tilburg •Lindbergh, Strindberg •Wittenberg • Vicksburg • Pittsburgh •Ginsberg • Johannesburg •Königsberg • Gettysburg • Freiburg •Heidelberg • Heisenberg • iceberg •Bromberg, homburg, Romberg •Gothenburg • Warburg • Jo'burg •Gutenberg • Duisburg • Magdeburg •Brandenburg • Hindenburg •Mecklenburg • Wallenberg •Orenburg • Nuremberg •Luxembourg • St Petersburg •Williamsburg • Schoenberg •Würzburg • Esbjerg

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