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Just like a snowflake, it could be said that no two icebergs are exactly alike. Each iceberg is defined by its birth, establishing its size and shape as it sets off on a long journey.
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Profile: Ijsberg
The life and times of Arctic icebergs
By Holly Gordon
Common name: Iceberg, ‘ Berg, Bergie
Scientific name: Arctic iceberg
Average height: ranges from one metre above sea level to more than 75
metres above sea level
Did you know? The term iceberg most likely came from the Dutch term "ijsberg," which
means "ice mountain" |
Did you know?
It´s not uncommon to see an iceberg
moving directly against strong winds because 90 percent of its mass below sea level
is drifting with the ocean current, not the wind.
A secret World War II program, Habbakuk,
planned to make aircraft carriers out of icebergs. The program began in Jasper and
Banff, but was soon abandoned.
When birds take flight from resting on an
iceberg it´s a good sign that the iceberg will soon roll.
The largest iceberg ever recorded in the
Northern Hemisphere was found near Baffin Island in 1882. It was 13 kilometres long,
six kilometres wide, 20 metres above sea level and had a mass of nine billion tonnes.
It´s not uncommon to see an iceberg
moving directly against strong winds because 90 percent of its mass below sea level
is drifting with the ocean current, not the wind.
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Physiology
An iceberg is a piece of glacial
ice that can measure one metre or more above sea level. When an iceberg is in the water,
approximately 90 percent of its mass is below sea level.
Icebergs are normally white because of all the tiny air bubbles in the ice. The bubbles reflect
all light waves, giving the iceberg a white appearance. An iceberg looks blue in colour when
the ice is bubble-free. This is because when white light, made up of all colours combined,
passes through the ice more red light is absorbed than blue light, causing any light that has
passed through a reasonable thickness of ice to appear blue.
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Height (m) |
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Length (m) |
| Growler (the size of a small car) |
less than one |
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less than five |
| Bergy bit (the size of a house) |
1 to 4 |
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5 to 14 |
| Small |
5 to 15 |
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15 to 60 |
| Medium |
16 to 45 |
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61 to 122 |
| Large |
46 to 75 |
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123 to 21 |
| Very large |
over 75 |
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over 213 |
There are two classes of icebergs: tabular and non-tabular. A tabular iceberg has steep
sides and a flat top. It looks more like a large, flat piece of ice than one would normally
picture, and its length-to-height ratio is less than 5:1. A non-tabular iceberg is as it
sounds – any iceberg that does not conform to the tabular characteristics. It usually
becomes that way because its flat top has eroded into another shape.
There are five kinds of non-tabular icebergs: dome, pinnacle, wedge, dry dock and blocky.
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Pinnacle: one or more spires. |
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Wedge: one steep vertical side that slopes down
to the opposite side. |
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Blocky: steep, vertical sides and a flat top. |
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| Dry dock: erosion has created a U-shaped slot
or channel near or at sea level. Each side of the dry dock normally has a column
or pinnacle. |
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Habitats/Behaviours
An Arctic iceberg breaks off from a glacier and
can be found floating in the water or aground. Icebergs themselves don't exist for many years,
but the glaciers that calve them are thousands of years old.
Iceberg timeline:
1,000 B.C.: Snow falls on arctic ice caps and, during the next several months, turns into
firn – a granular form of snow.
950 B.C.: The firn is compressed into dense ice because of the added firn and snow that
have accumulated on top of what fell 50 years earlier.
Between 950 B.C. and 2002 A.D.: The weight of the ice cap forces the ice to slowly flow
seaward.
1993 A.D.: Icebergs are calved – break off of the glacier – because they are
weakened by the rising and falling tides on the coast.
1996 A.D.: The icebergs calved three years previous melt. An estimated one percent of icebergs
make it as far as the Atlantic Ocean. If an iceberg travels that far, it will melt within
months from the warm waters. If an iceberg stops drifting in Baffin Bay, however, it can
take more than four years for the iceberg to melt.
Range
Western Greenland's glaciers calve 90 percent of all icebergs found in Newfoundland's waters.
This means that between 30,000 and 40,000 icebergs are calved annually.
After calving usually on the west coast of Greenland, icebergs drift to the coast of Newfoundland,
which is about 1,800 nautical miles.
The average iceberg drift speed is about 0.7 kilometres per hour, but this is influenced
by factors including iceberg size, shape, currents, waves and wind. They travel in the Baffin
Current, then the Labrador Current and finally reach the Grand Banks of Newfoundland. Once
they reach the Grand Banks, icebergs drift either eastward – north of the Flemish Cap – or
southward between the Flemish Cap and the Grand Banks – also known as Iceberg
Alley.
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