Iceberg

s at Cape York, Greenland]] 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. 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.

Etymology

from the Ross Ice Shelf]] The word "iceberg" is a partial loan translation from Dutch ijsberg, literally meaning ice mountain, cognate to Danish Isbjerg, German Eisberg, Low Saxon Iesbarg, Swedish Isberg and Norwegian Isfjell.

Overview

Because the density of pure ice is about 920 kg/m³, and that of sea water about 1025 kg/m³, typically only one-ninth 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 "", for a problem or difficulty that is only a small manifestation of a larger problem.

Icebergs generally range from above sea level and weigh . The tallest known iceberg in the North Atlantic was above sea level, reported by the USCG icebreaker East Wind in 1958, making it the height of a 55-storey building. These icebergs originate from the glaciers of western Greenland, and may have an interior temperature of .

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 , with a surface area of . The mass was estimated around three billion tonnes. The largest iceberg on record was an Antarctic tabular iceberg of over [] sighted west of Scott Island, in the South Pacific Ocean, by the USS Glacier on November 12, 1956. This iceberg was larger than Belgium.

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.

Recent large icebergs

Iceberg B-15 , 2000 Iceberg A-38, about , 1998 Iceberg B-15A, , broke off 2003 Iceberg C-19, , 2002 Iceberg B-9, , 1987 Iceberg D-16, , 2006 Ice sheet, , broken off of Petermann Glacier in northern Greenland on Aug 5, 2010, considered to be largest Arctic iceberg since 1962. About a month later, this iceberg split into two pieces upon crashing into Joe Island in the Nares Strait next to Greenland. Iceberg B-17B , 1999, shipping alert issued December 2009

Shape

In addition to size classification, Icebergs can also be classified on the basis of their 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. This type of iceberg can be quite large, as in the case of Pobeda Ice Island. Antarctic icebergs formed by breaking off from an ice shelf, such as the Ross Ice Shelf or Filchner-Ronne Ice Shelf, are typically tabular. The largest icebergs in the world are formed this way. of Iceberg A-38 off Ronne Ice Shelf]]

Non-tabular icebergs have different shapes, and include:

Dome: An iceberg with a rounded top.

Pinnacle: An iceberg with one or more spires.

Wedge: An iceberg with a steep edge on one side and a slope on the opposite side.

Dry-Dock: An iceberg that has eroded to form a slot or channel.

Blocky: An iceberg with steep, vertical sides and a flat top. It differs from tabular icebergs in that its shape is more like a block than a flat sheet.

melty: An iceberg that is starting to melt or has water on the top.

Monitoring

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 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:

A – longitude 0° to 90° W (Bellingshausen Sea, Weddell Sea)

B – longitude 90° W to 180° (Amundsen Sea, Eastern Ross Sea)

C – longitude 90° E to 180° (Western Ross Sea, Wilkes Land)

D – longitude 0° to 90° E (Amery Ice Shelf, Eastern Weddell Sea)

Iceberg B15 calved from the Ross Ice Shelf in 2000 and initially had an area of . It broke apart in November 2002. The largest remaining piece of it, Iceberg B-15A, with an area of , 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 away.

History

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 provides the "limits of all known ice" in that vicinity to the maritime community.

Technology history

; a smudge of red paint much like the Titanic's stripe was seen near the base.]]

Before April 1912 there was no system in place to track icebergs to guard ships against 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, ice-flow, 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.

See also

Drift ice station

Ice drift

Polar ice cap

Polar ice packs

Polynya

Sea ice

Shelf ice

References

External links

Iceberg Finder Service for east coast of Canada

Icebergs of The Arctic and Antarctic

Category:Dutch loanwords Category:Physical oceanography Category:Ice in transportation Category:Bodies of ice