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Ice Islands: Giant Bergs Adrift

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By Gregory S. Stone Photographs by Wes Skiles

A giant iceberg tests a diver's resolve with hidden caves, lethal temperatures, and ice explosions. Far from lifeless, icebergs shelter a startling swirl of sea life.

The Antarctic sun glowed red on the horizon at 1 a.m. A mile and a half (2.4 kilometers) from the deck of Braveheart an iceberg the size of six city blocks—the iceberg we'd been tethered to just hours before—heaved upward, one end pausing high in the air like the bow of a foundering ship. When it crashed back down, waves swept through the waters off Cape Hallett. As the boat rocked, the iceberg rose again, and the upper end of it seemed to explode. It was not long before ice shards covered two square miles like shattered crystal.

Such an event has rarely been recorded by humans, and it reinforced our sense of the tremendous power, complexity, and danger of the Antarctic icebergs we had come to study. One in particular was cruising the Ross Sea some 125 miles (201 kilometers) from where we were.

Its name was B-15B, a 1,900-square-mile (3,058-square-kilometer) chunk of the original B-15, which, when it calved from the Ross Ice Shelf in March 2000, had an upper surface area of about 4,500 square miles (7,242-square-kilometer)and was estimated to contain enough fresh water to supply the United States for five years.

A berg with the dimensions of B-15 comes along once or maybe twice in a lifetime. The National Ice Center in Suitland, Maryland, which has been tracking Antarctic icebergs with satellite mapping techniques for 25 years, has never recorded a berg as big. For nine years satellite images recorded the cracks in the Ross Ice Shelf as they spread and set B-15 loose.

It took only a month after B-15 was born for photographer Wes Skiles and me to decide to launch an expedition to study it. Antarctica's large, tabular bergs create habitat for penguins and seals that climb on ice ledges at the waterline and for seabirds that roost on them. At their edges and in caves that form along them, nutrients mix and fuel the growth of tiny marine plants called phytoplankton, the basis of the marine food web. As they drift and melt, the bergs leave physical and biological wakes that may encourage the concentration of krill, fish, jellyfish, whales, and seals.

In the months after B-15 calved, its fragments appeared headed for the shipping lanes supplying McMurdo Station, where the U.S. Antarctic Program operates year-round. And B-15A, the largest remnant of B-15, was positioned in a way that impeded more than 170,000 breeding pairs of emperor and Adélie penguins from traveling back and forth to their rookery at Cape Crozier.

We recruited an 18-member team of divers, environmental scientists, and a rough-and-ready New Zealand crew, and on January 17, 2001, in the 129-foot (39 meter) steel-hulled Braveheart, we set sail from Lyttelton, New Zealand. More than 2,000 miles (3,219 kilometers) and two weeks later (the equivalent of traveling from Miami to Los Angeles at seven miles an hour through gale-whipped ocean) we reached the remote, ice-choked waters of the Ross Sea.

In the end an unusually bad season of pack ice kept us from reaching B-15B in Braveheart. But for the five of us who dived some 90 times into the frigid waters, the bergs that littered the Ross Sea—many of them smaller chunks of B-15—provided more than seven weeks of science, exploration, and adventure.

We wanted to explore underwater places too dangerous for open-circuit scuba gear, so we used state-of-the-art rebreathing equipment that allows divers to remain safely at greater depths for longer periods by recycling exhaled breath. The water temperature presented separate problems. Seawater at 29.5°F (minus 1.4°C) sucks away body heat so quickly that a naked person would die in minutes. We wore two layers of underwear, dry suits, electric heaters, and two hoods. Still, most of the time in the water our hands and feet throbbed with pain. It took several months after returning home for some of us to recover complete feeling in faces, fingers, and toes.

Although the symptoms of frostbite and neuralgia have faded, the wonder of the expedition has not. Our observations support the research that indicates Antarctica's monstrous bergs, some of which can last for years, are a major factor in the biology of the Ross Sea. As they calve, move, and melt, they play an important role in the operation of the entire global ocean system. That system covers 70 percent of Earth, and what we are learning in Antarctic waters will fundamentally affect what we know about the future of our planet.

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In More to Explore the National Geographic magazine team shares some of its best sources and other information. Special thanks to the Research Division.

B-15. C-5. A-6. A bingo game in progress? No, these are names assigned to icebergs found in the Antarctic. The National/Naval Ice Center in Suitland, Maryland, names and tracks icebergs that are at least ten nautical miles long. The letter in the name is derived from the Antarctic quadrant in which the berg is first sighted: Quadrant A faces the Atlantic, B faces the Eastern Ross Sea, C faces Australia, and D faces the Indian Ocean. The assigned number represents the number of icebergs calved in that quadrant since 1976, the year the center began tracking icebergs by satellite. For example, iceberg B-15 is the 15th iceberg calved and tracked by the ice center in quadrant B. The iceberg designated B-15B is the second fragment to calve off of B-15.

—Abby Tipton

The National/Naval Ice Center
This website links you to satellite pictures of icebergs throughout the Arctic and Antarctica (including B-15) as well as to other sources of iceberg information.

United States Antarctic Program
Home page for the the National Science Foundation's U.S. Antarctic Program, which supports polar research conducted by scientists selected from universities and other research institutions.

Antarctic Newspaper
Newspaper published during the austral summer for the U.S. Antarctic Program at McMurdo Station, Antarctica.

Real-time Iceberg Photos
Part of the Space Science and Engineering Center at the University of Wisconsin, this Antarctic Projects Home Page provides near real-time and archived iceberg information.


Stonehouse, Bernard. The Last Continent: Discovering Antarctica. SCP Books, 2000.

“U.S. Antarctic Program, 1998-1999,” Office of Polar Programs, National Science Foundation, v. 56, 1998.


Heacox, Kim. Antarctica: The Last Continent. National Geographic Books, 1998.

Lewis, David. “Voyage to the Antarctic,” National Geographic (April 1983), 544-562.

Ellis, William S. “Tracking Danger With the Ice Patrol,” National Geographic (June 1968), 780-793.

Byrd, Richard Evelyn. “Our Navy Explores Antarctica,” National Geographic (October 1947), 429-522.


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