Icebergs
Icebergs are thick masses of ice floating in the ocean. They form when large chunks of ice break off a glacier or an ice shelf and float free in the sea. This is called calving. Many new icebergs were formed in 2002, with the break up of the Larsen B ice shelf.
Icebergs in Antarctica
Dr Mike Williams from NIWA explains where the icebergs from Antarctica come from and how they were formed.
Icebergs can vary in size, but the largest-known iceberg, B15A, was 296 km long and 38 km wide when it broke off the Ross ice shelf in 2001. This is about the same size as Jamaica –10,600 km².
B15 in McMurdo Sound
Dr Mike Williams from NIWA explains what effect the iceberg B15 had on the penguin colony nearby when it blocked the inlet to McMurdo Sound.
This sounds huge – but you wouldn’t have been able to see the whole thing as around 90% of an iceberg is actually under water.
Tip of the iceberg
The tip of an iceberg which is visible above the waterline is usually only about 1/7 or 1/8 of the mass of an iceberg. Seawater is slightly denser than ice and this means that the iceberg floats with most of its mass below the surface. In comparison a cork, which has a density of about 20% that of water, floats close to the water surface. Ice has about 90% of the density of water but the density of seawater is also influenced by the temperature and salinity.
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Download a PDF of the two images side by side for easy comparison.
The reason why ice floats and is lighter than water is that a certain mass of ice occupies more space than the same mass of water. This is related to the characteristics of hydrogen bonds.
Floating icebergs
Icebergs are thick masses of ice floating in the ocean. The reason why ice floats and is lighter than water is that a certain mass of ice occupies more space than the same mass of water. This is related to the characteristics of hydrogen bonds. This iceberg is floating off the Otago coastline.
In 2006, icebergs were sighted off New Zealand’s Otago coastline – the first time they’d been seen so far north in many years. Where did they come from? What is an iceberg, anyway?
Did you also know that all icebergs over 1900 m along at least one axis are monitored by the US National Ice Center and given names to assist with tracking.
Naming icebergs
Dr Mike Williams from NIWA explains how icebergs are named and that icebergs can have siblings as well.
Useful link
The varied sights and sounds of Antarctic icebergs begin to reveal themselves in this Radio NZ podcast with NIWA scientist and Deep South National Science Challenge director, Dr Mike Williams: Voice of the iceberg 2.
