Icebergs regularly break off from glaciers in the Arctic and make their way south to the North Atlantic Ocean, where they can come into contact with ships. The number of icebergs found in the North Atlantic Ocean changes from year to year.

Chart courtesy National Geographic Maps
  • A deep, cold ocean current flows down from the North Pole, around the Canadian province of Newfoundland and Labrador, to meet the warm Gulf Stream traveling north from the Gulf of Mexico. Called the Labrador Current, it passes by the Arctic’s premier iceberg nursery off the coast of west Greenland. There, icebergs calve in great numbers, breaking off glaciers to float freely in the ocean. They drift northward up the coast until they meet the Labrador, then ride south in huge masses toward Newfoundland. Nowhere else in the world does this much ice intersect major shipping routes. The region deserves its nickname: Iceberg Alley.

    Icebergs, fog, severe storms, and ocean traffic make Iceberg Alley one of the world’s most dangerous shipping areas. Temperature differences between the Labrador Current and the Gulf Stream, up to 68°F (20° C), produce dense fog and unsteady seas.

    The officers of Titanic were well aware of the risks. A 1909 pilot’s guide supplied to the ship stated, “One of the chief dangers in crossing the Atlantic lies in the probability of encountering masses of ice, in the form of both icebergs and extensive fields of solid compact sea ice. Ice is more likely to be encountered in this route between April and August, both months inclusive, than at other times.” In fact, 1912 saw the heaviest ice for any April in the then-young century, a record that stood until 1972.

    Forming the Ice Patrol

    In the wake of the Titanic disaster, the International Convention for the Safety of Life at Sea (SOLAS) created the International Ice Patrol (IIP) in 1913. SOLAS mandated a 24-hour radio watch, boat drills, and lifeboats for all passengers on ships navigating Iceberg Alley. The IIP’s mission remains to “monitor the extent of the iceberg danger near the Grand Banks of Newfoundland during the ice season, and broadcast the location of the southeastern, southern, and southwestern limits of all known ice to interested shipping.”

    Ice patrollers survey 1.3 million square kilometers (half a million square miles) by air each day, feeding data into a computer model of the Limit of All Known Ice (LAKI). They then broadcast the LAKI report via radio and the Internet, recommending specific lanes for safe passage.

    Ice continues to be a shipping hazard in Iceberg Alley and across the North Atlantic, with hundreds of collisions since 1912. But thanks in part to the IIP and improved radio communications, no single incident has resulted in more than a hundred casualties.

    • The average iceberg is 1,982 cubic meters (70,000 cubic feet)—about 840,000 ice cubes.
    • Seven-eighths of an icebergs mass is below the waterline.
    • Melting an average iceberg takes the specific heat of 9.1 million liters (2.4 million gallons) of gasoline.
    • It takes 1,724 metric tons (1,900 tons) of TNT to blow up an average iceberg.
    • The tallest known iceberg in the North Atlantic was 168 meters (550 feet) high, sighted off Greenland in 1967.
    • Ice islands from Antarctica can reach the size of the U.S. state of Rhode Island.
    • Icebergs float because they are freshwater, which is less dense than saltwater.
    • Meltwater flowing off icebergs sustains whole colonies of krill (tiny shrimp), making them a magnet for fish, whales, seals, and polar bears.
    • Icebergs are most dangerous to ships when they turn over in the water. Don't go near them in a small boat!
  • Term Part of Speech Definition Encyclopedic Entry
    Arctic Noun

    region at Earth's extreme north, encompassed by the Arctic Circle.

    Encyclopedic Entry: Arctic
    casualty Noun

    person who has been injured or killed in a specific incident.

    coast Noun

    edge of land along the sea or other large body of water.

    Encyclopedic Entry: coast
    current Noun

    steady, predictable flow of fluid within a larger body of that fluid.

    Encyclopedic Entry: current
    data Plural Noun

    (singular: datum) information collected during a scientific study.

    fog Noun

    clouds at ground level.

    Encyclopedic Entry: fog
    glacier Noun

    mass of ice that moves slowly over land.

    Encyclopedic Entry: glacier
    Gulf Stream Noun

    warm current that starts in the Gulf of Mexico and travels along the eastern coast of the U.S. and Canada before crossing the North Atlantic Ocean.

    iceberg Noun

    large chunks of ice that break off from glaciers and float in the ocean.

    Encyclopedic Entry: iceberg
    Iceberg Alley Noun

    area in the North Atlantic Ocean with a large number of icebergs.

    International Ice Patrol Noun

    organization that keeps track of the number, size, and movement of icebergs in order to warn ships.

    navigate Verb

    to plan and direct the course of a journey.

    North Pole Noun

    fixed point that, along with the South Pole, forms the axis on which the Earth spins.

    Encyclopedic Entry: North Pole
    ocean Noun

    large body of salt water that covers most of the Earth.

    Encyclopedic Entry: ocean
    province Noun

    division of a country larger than a town or county.

    Encyclopedic Entry: province
    sea ice Noun

    frozen ocean water.

    shipping route Noun

    path in a body of water used for trade.

    storm Noun

    severe weather indicating a disturbed state of the atmosphere resulting from uplifted air.

    temperature Noun

    degree of hotness or coldness measured by a thermometer with a numerical scale.

    Encyclopedic Entry: temperature
    Titanic Noun

    luxury cruise ship that sank in the North Atlantic Ocean in 1912.