Icebergs come in many sizes, from very large (over 240 feet tall) to the “growler” (under 3 feet tall).

Erik Hecht/500px/National Geographic Creative

STANDARDS

CCSS: 6.RP.A.2, MP2, MP3

TEKS: 6.4B, 6.4C

Breaking the Ice

A giant iceberg recently split off Antarctica, hinting at the possible future of polar ice

At first, the crack crept slowly along the Antarctic Peninsula. This long landmass juts out from the frozen continent, arching toward South America like a bird’s wing. Huge platforms of floating ice called ice shelves extend from the coast into the sea.

Then, in 2014, the crack began expanding. By early 2017, it stretched 150 kilometers across an ice shelf known as Larson C. It was growing at the rate of five football fields a day. Finally, on a cloudy winter day in July, the crack reached the end of its journey, causing a big chunk of Larson C to break free.

A.Fleming/British Antarctic Suvey (ice shelf crack); Jim McMahon/Mapman (map and globe)

The resulting iceberg, named A68, is one of the largest ever recorded. At 200 meters thick, it’s nearly as tall as the Washington Monument. Its surface area is the size of Delaware, and its weight is close to 1 trillion tons. That’s enough water to supply New York City for a century!

“It’s a whopping hunk of ice,” says Christina Hulbe, a glaciologist at the University of Otago in New Zealand. She and other experts are keeping an eye on A68 and the ice shelf it came from. The enormous iceberg may be nothing to worry about. Or it could hint at more destruction to come.

CYCLES OF ICE

In some ways, A68 isn’t so strange. Ice is constantly calving, or breaking off from ice shelves. In fact, A68 was the 68th new iceberg that formed off the Antarctic Peninsula this year.

Iceberg calving is part of Antarctica’s natural ice cycle. The cycle begins when snow piles up in the continent’s interior. As it condenses, the snow slowly flows toward the coast in rivers of ice called glaciers. The glaciers in turn feed the ice shelves, which shed their ice in the form of icebergs. Eventually, these broken blocks melt and evaporate to make snow, starting the cycle again.

“That’s completely normal,” says Bryn Hubbard, a professor of glaciology at Aberystwyth University in Wales. What’s not normal is A68’s size. An iceberg that big has never broken off Larson C before, so scientists aren’t sure what to expect.

“The question is: What does it mean for the rest of the ice shelf now that this big piece is gone?” says Hubbard. Will Larson C regrow to replace the ice that was lost? Or is it heading toward a breakup?

Michael Nolan/Robert Harding/National Geographic Creative

CATASTROPHIC COLLAPSE

Ice shelves have disappeared before. In 1995, Larson C’s northern neighbor, Larson A, suddenly shattered into thousands of icebergs. In 2002, Larson B—which sat between Larson A and C—collapsed in the same way.

“It was shocking,” says Hulbe. She observed the dramatic scene in images from an Earth-orbiting spacecraft. “The surface of the ocean looked like a blue slushy,” she says.

Hulbe and her colleagues studied these events. Using satellite data and computer models, they found that warming temperatures in Antarctica had caused the snow on the ice shelves to melt. The meltwater streamed into cracks, where it refroze. This deepened the cracks and weakened the ice.

Scientists are now monitoring Larson C to see if it’s similarly vulnerable. So far, observations and models paint a hopeful picture. “But the jury’s still out,” Hubbard says. “We’re all ready to be proven wrong.”

AN UNCERTAIN FUTURE

Antarctica’s ice is melting faster because of climate change, an increase in Earth’s average temperature. But scientists hope that the melting can be slowed down. People around the world can help by producing fewer greenhouse gases. These gases—released when burning fuels like gasoline and coal—warm Earth’s atmosphere.

If the Larson C ice shelf crumbles completely, the consequences could be dire. Ice shelves act like plugs, slowing the flow of glaciers into the sea. Remove the plugs and the ice drains faster. 

“These ice shelves are like canaries in a coal mine,” says Eric Rignot, a glaciologist at the University of California, Irvine. “Once they start breaking up, it’s a sign of trouble for Antarctic ice.”

As Antarctica continues to warm, “that warming will extend farther and farther south, where there are even bigger ice shelves holding back even bigger glaciers,” predicts Rignot. Ice in West Antarctica, for instance, covers an area twice the size of Texas. If it vanishes, it will raise the sea level by roughly 10 feet, drowning coasts around the world.

“We don’t want that to happen,” says Rignot. “And we can still stop it. But we have to act now.”

Use the information below to compare the sizes of different icebergs with each other and geographic areas with similar surface areas. Round  your answers to the nearest whole number. Record your work and answers on our answer sheet.

A. How many Delawares could fit on iceberg B15?

B. How many Hawaiis could fit on iceberg B15?

C. Which comparison do you think is better? Explain.

A. Describe in words how iceberg D16’s size compares with San Francisco?

B. Describe in words how the size of iceberg D16 compares with Delaware?

C. Would it be better to compare the area of iceberg D16 with San Francisco or Delaware? Explain your answer and calculate how many of your chosen place would fit on iceberg D16.

About how many A68’s equal the size of Hawaii?

About 14,000,000 square kilometers of ice cover Antarctica. About how many A68s is that? About how many B15s is that?

Which place listed in the “Area Comparisons” diagram best conveys the size of A24?

Text-to-Speech