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Iceberg

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An iceberg is a massive piece of fresh water ice. It breaks off from a glacier or an ice shelf to float freely in open water. This process of breaking off is called calving.

Iceberg A-38
Iceberg A-38

Because of the way ice floats, only about one-tenth of an iceberg's volume is visible above the surface. This occurs due to Archimedes's Principle of buoyancy. The density of pure ice is about 920 kg/m3, while seawater is much denser. This creates the common expression "tip of the iceberg." It describes a situation where only a small part of a larger issue is visible.

Icebergs lose mass through two main processes: melting and calving. Melting is often driven by the ocean rather than solar radiation. Scientists model ocean-driven melting by looking at the velocity between the iceberg and the ocean. They also consider the temperature difference between the water and the ice. Waves also cause erosion by impacting the iceberg.

As the ice melts, trapped air bubbles are released. These bubbles can make a popping or fizzing sound known as "Bergie Seltzer." This sound can actually help scientists study how the ice is melting. Calving happens when the ice fractures into new pieces. This fracturing changes the mass, volume, and stability of the iceberg.

Grotto in an iceberg
Grotto in an iceberg

Icebergs are classified by their size and their shape. The International Ice Patrol uses specific classes for size. Small chunks are called "growlers," which are less than 1 meter high. Larger pieces are called "bergy bits," which are between 1 and 5 meters high. Very large icebergs can exceed 75 meters in height.

Iceberg Shape
Iceberg Shape

Shapes also vary significantly. Tabular icebergs have flat tops and steep sides, looking like a plateau. These often come from Antarctic ice shelves. Other shapes include domes with rounded tops or pinnacles with spires. Some icebergs are wedge-shaped, while others are blocky.

Blue Tabular Iceberg
Blue Tabular Iceberg

Stability is a major concern because icebergs can capsize without warning. As an iceberg melts or breaks, its center of gravity changes. This can cause the iceberg to flip over suddenly. This is especially common when an iceberg is young and first calves from a glacier. Large icebergs can even cause "glacial earthquakes." This happens when a large piece flips back onto the glacier face. Such an event can release as much energy as an atomic bomb.

Tracking icebergs has a long and important history. Before 1914, there was no formal system to monitor them. This lack of tracking led to many ship collisions. In 1912, the RMS Titanic sank after hitting an iceberg. This tragedy killed more than 1,500 people. In response, maritime nations formed the International Ice Patrol in 1913. The group monitors currents, ice-flow, and ocean temperatures. They provide data to help ships stay safe near the Grand Banks of Newfoundland.

Titanic iceberg
Titanic iceberg

Modern technology allows us to monitor icebergs from great distances. In the 1940s, scientists tested the use of radar for detection. By the 1970s, ice-breaking ships used satellite photographs to track ice. Today, we use advanced satellites like RADARSAT-1 and ENVISAT. These use synthetic aperture radar (SAR) to see through bad weather. SAR sends microwave energy to the ocean and records the reflections.

Iceberg A22A, South Atlantic Ocean
Iceberg A22A, South Atlantic Ocean

The U.S. National Ice Center also monitors ice worldwide. They name Antarctic icebergs using a letter and a number. For example, the letter indicates where the iceberg originated.

Research on Iceberg B-15A by Josh Landis, National Science Foundation (Image 4) (NSF)
Research on Iceberg B-15A by Josh Landis, National Science Foundation (Image 4) (NSF)

Icebergs are much larger than they might appear. The largest iceberg on record was an Antarctic tabular iceberg. It was sighted in 1956 and was larger than the country of Belgium. In 2000, a massive iceberg named B-15 was measured in Antarctica. These icebergs can have masses exceeding 10 million tonnes. Some icebergs even show many colors. They can appear blue, green, or even rainbow-colored. This is caused by seawater, algae, or a lack of air bubbles.

Iceberg in the Arctic with its underside exposed
Iceberg in the Arctic with its underside exposed

Sediment can even turn an iceberg black. Some people have even proposed towing icebergs to provide fresh water to other regions.

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🖼️ Images & Media (14)
File:Iceberg in the Arctic with its underside exposed.jpg
Iceberg in the Arctic with its underside...
File:Blue Tabular Iceberg.jpg
Blue Tabular Iceberg.jpg
File:Iceberg from overhead IMG 0320.jpg
Iceberg from overhead IMG 0320.jpg
File:Research on Iceberg B-15A by Josh Landis, National Science Foundation (Image 4) (NSF).jpg
Research on Iceberg B-15A by Josh Landis,...
File:Grotto in an iceberg.jpg
Grotto in an iceberg.jpg
File:Iceberg Shape.svg
Iceberg Shape.svg
File:Antarctic Sound-2016-Iceberg 02.jpg
Antarctic Sound-2016-Iceberg 02.jpg
File:Titanic iceberg.jpg
Titanic iceberg.jpg
File:Burton Island, Atka, and Glacier push iceberg in McMurdo Sound (827218l).jpg
Burton Island, Atka, and Glacier push...
Singing iceberg.oga
File:Iceberg A22A, South Atlantic Ocean.jpg
Iceberg A22A, South Atlantic Ocean.jpg
File:Scenic_view_of_Greenland_icebergs_in_Baffin_Bay_in_Disko_Bay_07.jpg
Scenic_view_of_Greenland_icebergs_in_Baffi...

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