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All about icebergs: How these majestic yet menacing chunks of ice threaten shipping

Icebergs are natural wonders that inspire a sense of fascination but also pose dangers to the international shipping community.

Icebergs are pieces of ice that formed on land and float in an ocean or lake. The North Atlantic and the cold waters surrounding Antarctica are home to most of the icebergs on Earth.

An iceberg is born when chunks of ice calve, or break off, from glaciers, ice shelves or a larger iceberg. The large ice masses travel with ocean currents, sometimes smashing up against the shore or getting caught in shallow waters.

“Icebergs more or less do what the current tells them,” said Richard Alley, Evan Pugh professor of geosciences at Penn State.


This floating iceberg off southeast Greenland is one of over 10,000 calved annually from the island's glaciers. (Flickr Photo/David Stanley)

According to Scott Weese, a meteorologist with the Canadian Ice Service, icebergs are classified by size. The term iceberg refers to chunks of ice larger than 16 feet (5 meters) across.

Smaller icebergs, known as bergy bits and growlers, can be especially dangerous for ships because they are harder to spot. Icebergs also come in a variety of shapes, Weese said, such as tabular, domed and wedge.

Icebergs typically migrate from the Arctic Circle to “Iceberg Alley,” which is an area stretching from the coast of Labrador to the northeast coast of the island of Newfoundland.

In April 2017, tourists flocked to the town of Ferryland -- which is south of St. John's on the east coast of Newfoundland and Labrador -- to see a massive iceberg that grounded just off shore. The Canadian Ice Service classified it as "large," which means it has a height of 151-240 feet and is between 401 and 670 feet long.

According to Alley, the relatively early appearance of the iceberg in Ferryland is due to unusual storm activity that buffered the iceberg off its typical course and caused it to take a shortcut across the Canadian coast. Peak iceberg season is from May to early July.

However, Alley said, global climate change may be contributing to a broader trend of icebergs making appearances early in the season.

According to AccuWeather Senior Meteorologist Brett Anderson, climate change is increasing the rate at which ice is breaking off glaciers in Greenland.

“This year, there has been a high number of icebergs as more ice has broken off glaciers,” Anderson said. “I would say this would become a problem for shipping.”

For ships navigating through iceberg-laden waters, the phrase “just the tip of the iceberg” is literally true. For most icebergs, according to, the part below the water is three to nine times the height above the water.


This March 2017 photo released by the U.S. Coast Guard and made by a robotic camera aboard a reconnaissance aircraft shows icebergs floating near the Grand Banks of Newfoundland in the North Atlantic Ocean. (Photo/U.S. Coast Guard via AP)

In addition, Alley said, icebergs can break up or roll over, which can be hazardous to passing ships.

After the Titanic sank near Newfoundland in 1912 after striking an iceberg, the United States and 12 other countries formed the International Ice Patrol to warn ships of icebergs in the North Atlantic.

The International Ice Patrol uses airplanes and radars to track icebergs that float into major shipping lanes. The U.S. National Ice Center uses satellite data to monitor icebergs near Antarctica. However, it only tracks icebergs larger than 500-square meters.

The International Ice Patrol reported that 648 icebergs have been seen in the trans-Atlantic shipping lanes as of late April 2017. That's compared to an average 212 icebergs during that period in a typical year.