International Ice Patrol (IIP)
Frequently Asked Questions
Icebergs
| Q. |
Where do North Atlantic icebergs come from?
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| A. |
The principal origin of those icebergs that reach the North Atlantic
Ocean are the 100 or so major tidewater glaciers of West Greenland.
Between 10,000 to 15,000 icebergs are calved each year, primarily from
20 major glaciers between the Jacobshaven and Humboldt Glaciers.
Since icebergs originate from Glaciers, they are composed of fresh
water. As described in the other FAQs, glaciers are formed by
thousands of years of snowfall accumulation which eventually is compressed
into ice. It is estimated that these glaciers account for 85% of the icebergs
which reach the Grand Banks of Newfoundland. Other sources of icebergs are the East
Greenland glaciers, which produce about half the amount of icebergs as the West
Greenland glaciers, but account for only 10% of the icebergs reaching the Grand Banks. The
remaining 5% are thought to come from glaciers and ice shelves of northern Ellesmere
Island.
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| Q. |
What is the life cycle of an iceberg?
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| A. |
The life cycle of a typical iceberg found in the North Atlantic today
might look something like this:
| TIME LINE | ICEBERG DEVELOPMENT |
|---|
| 1,000 B.C. | Snow/Firn |
| 950 B.C. | Ice/Glacier |
| -- | Glacier movement |
| 1998 A.D. | Calving |
| 2001 A.D. | Iceberg melt |
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| Q. |
How many icebergs last long enough to reach the Atlantic shipping lanes?
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| A. |
The mean number of icebergs passing south of 48 N is 482 icebergs with a standard
deviation of 492 icebergs. Therefore, yearly totals are highly variable and are
subject to highly variable climatic factors.
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| Q. |
Where is iceberg alley?
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| A. |
The area we call "Iceberg Alley" is located about 250 miles east and
southeast of the island of Newfoundland, Canada. Iceberg Alley is usually
considered to be that portion of the Labrador Current, that flows southward
from Flemish Pass, along the eastern edge of the Grand Banks of Newfoundland,
to the Tail of the Banks. This area extends approximately from 48 to 43 degrees
North Latitude at 48 degrees West longitude. Icebergs and sea ice flowing south
from Iceberg Alley created the Titanic disaster of 1912. This is the area of the
ocean we patrol and monitor most carefully.
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| Q. |
What are the shapes and sizes of icebergs?
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| A. |
ICEBERG SIZE CLASSIFICATION
| SIZE CATEGORY | HEIGHT(FT) | HEIGHT(M) | LENGTH(FT) | LENGTH(M) |
|---|
| Growler | less than 3 | less than 1 | less than 16 | less than 5 |
| Bergy Bit | 3-16 | 1-5 | 16-49 | 5<15 |
| Small | 16-49 | 5-15 | 49-197 | 15-60 |
| Medium | 50-148 | 16-45 | 198-394 | 61-120 |
| Large | 149-246 | 46-75 | 395-656 | 121-200 |
| Very Large | Over 246 | Over 75 | Over 656 | Over 200 |
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| Q. |
What are the most dangerous icebergs?
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| A. |
All icebergs are dangerous to shipping but depending on its size, shape
and location some icebergs can be more troublesome than others. Obviously,
icebergs nearest the Atlantic shipping lanes are of greatest concern to
mariners. Large icebergs, because of their great mass, can inflict the
most damage on a ship. However, they are usually easy to dectect on a
ship's radar and therefore can be avoided. On the other hand, the smaller
an iceberg, the harder it is for ships to detect and avoid. For example,
many growlers or bergy bits are mostly submerged and are about the size a
small vessel. These "hidden" icebergs can cause a significant amount of
damage to a vessel. Lastly, an iceberg's shape is a factor. A smoothed
iceberg can be more difficult to detect.
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| Q. |
What is the typical size of an iceberg in the North Atlantic Ocean?
|
| A. |
SIZE DISTRIBUTION OF ICEBERGS IN THE IIP OPERATION AREA FOR 1994 ICE SEASON
| SIZE CATEGORY | % OF TOTAL |
|---|
| Growler | 5.6% |
| Small | 15.3% |
| Medium | 15.3% |
| Large | 12.5% |
| Very Large | 2.8% |
| General(Size Unknown) | 48.5% |
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| Q. |
What is the largest iceberg ever recorded?
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| A. |
The largest icebergs (also referred to as ice islands) originate from
the vast ice shelves surrounding Antarctica (see National Ice Center's
list of
Antarctic Icebergs).
The largest known iceberg was from this region. Pictured below is a berg that was
roughly the size of the State of Rhode Island. IIP does not track Antarctic Icebergs.
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| Q. |
Besides the North Atlantic, where else might icebergs be found?
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| A. |
Icebergs are also commonly found around the ice shelves of Antarctica
(see National Ice Center's list of Antarctic Icebergs)
and a very small number of icebergs calve into the ocean in Alaska and in Siberia or
south of Franz Joseph Land in the Barents Sea.
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| Q. |
What is the extreme range of iceberg locations?
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| A. |
The grey shaded area is the normal range of iceberg distribution. The
extreme icebergs/growlers are indicated. Some of the notable extreme
icebergs are:
- In 1926, the southernmost known iceberg (a growler) reached 30-20 N, 62-32 W (about 150 nm from Bermuda).
- In 1883, a growler was located about 200 nm south of the Azores.
- In 1907, an iceberg was sighted about 100 nm southwest of Fastnet, Ireland.
- In 1912, a growler was seen about 75 nm east of Chesapeake Bay, USA.
- In 1912, the iceberg that the R.M.S. Titanic collided with was located at 41-46N, 50-12W.
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| Q. |
How much of an iceberg is below the water?
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| A. |
About 7/8ths of an iceberg is below the water line. This
figure is approximate. Although icebergs are similar, not all are the
same. Varying factors are iceberg density, water density etc. Keep in
mind we are talking about an iceberg's mass. Due to irregular iceberg
shapes, icebergs may have varying heights out of the water, but mass is
relatively consistent.
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| Q. |
Why were the 1999, 2005, and 2006 iceberg seasons so mild?
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| A. |
Currently we are not sure why these iceberg seasons were so mild. There are many contributing factors. The following response will focus on the 1999 iceberg season to provide a more thorough and detailed answer.
In
an average year, nearly 500 icebergs pass south of 48º N, the traditional
boundary below which icebergs are considered to be a menace to
transatlantic shipping. In 1999, 22 icebergs passed south of 48º N. In a
typical year, International Ice Patrol issues routine iceberg warnings to
mariners from February through July. In 1999, Ice Patrol issued no
warnings. Ice Patrol's aerial reconnaissance usually extends well into
August. In 1999, routine aerial reconnaissance was suspended at the end
of May.
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