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Ice, Ice & More Ice
Factfile |
 Ice, Ice & More Ice |
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Icebergs |
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Icebergs are pieces of floating ice that calve (break off) from ice shelves and glaciers. They can be of any size and are very common in the Southern Ocean. Believe it or not, scientists call small icebergs growlers (these are about the size of a small car) while the next biggest size of iceberg are called bergy bits (these are about the size of a house and no, we aren't making the name up!).
Calving icebergs split from the edge of Ross Ice Shelf - Australian Antarctic Division
Icebergs that calve from ice shelves are tabular (flat topped) but icebergs may also be described as dome-shaped, sloping, pinnacled, weathered or glacier bergs.
Tabular icebeg, Photo: HMS Endurance
The rule that 90% of an iceberg lie underwater is true and this is one of the reasons why they are so dangerous to Ships, as you can't see their shape under water. Another dangerous thing about icebergs is that because they move with the ocean currents, they cannot be marked on navigation charts.
When HMS Endurance is in Antarctica, the Ship's Meteorologists use radar and satellites to help them locate the position of drifting icebergs and this information is also passed on to all the ships in the area. Although HMS Endurance is of a special design so that it can withstand the shocks of constantly breaking through ice, every possible measure is taken to avoid a collision with an iceberg. The most famous Ship to hit an iceberg was the Titanic in 1912.
Scientists use a particular coding system for naming icebergs. When an iceberg is first sighted, it is given a letter of the alphabet (A,B,C or D) and a sequential number.
Satellite pic by NASA of icebergs
The letter of the alphabet relates to the particular sector of Antarctica in which the iceberg was first sighted:
A = Bellinshausen/Weddell Sea
B = Amundsen/Eastern Ross Sea
C = Western Ross Sea/ Wilkesland
D = Amery/ Eastern Weddell Sea
The sequential number explains the running order of the original sighting. For example, iceberg B-15 is the 15th iceberg to be sighted from sector B.
Ice shelves can produce tabular icebergs with bases that reach deeper than 300m. Seafloor images taken by Scientists across the shallow areas round Antarctica show deep gouges where icebergs have ploughed in the seafloor.
Eventually, storms, waves and warmer surface water all help to melt drifting icebergs, but they have been known to last over 6 years.
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