Breaking the 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.

The crack in the ice grew slowly at first. It crept up along the ice shelf. Ice shelves are huge platforms of floating ice that stick out from land into the sea. This ice shelf was on the Antarctic Peninsula. It’s a long landmass that stretches toward South America like a bird’s wing.

The crack began expanding in 2014. It stretched 150 kilometers across the Larson C ice shelf by 2017. The crack grew five football fields in length each day. In July, the crack reached the end of its journey. On a cloudy winter day, a big chunk of Larson C broke free.

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.

This chunk of ice became an iceberg that scientists named A68. It’s one of the largest icebergs ever recorded. A68 is 200 meters thick. That’s nearly as tall as the Washington Monument. Its surface area is the size of Delaware. It weighs 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. She studies glaciers at the University of Otago in New Zealand. Hulbe and other experts are keeping an eye on A68 and the ice shelf it came from. The huge iceberg may be nothing to worry about. Or it could hint at more destruction to come.

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?

In some ways, A68 isn’t so strange. Ice is constantly breaking off from ice shelves. This is called calving. 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 on top of the continent. As more snow falls, it creates pressure pushing the snow under it together. This forms ice. As the ice grows, its weight makes it slowly flow toward the coast. These rivers of ice are called glaciers. The glaciers in turn feed the ice shelves. Ice shelves then shed their ice in the form of icebergs. Eventually, these broken blocks melt and evaporate. The evaporation turns into snow, which starts the cycle again.

“That’s completely normal,” says Bryn Hubbard. He studies glaciers at Aberystwyth University in Wales. But A68’s huge size isn’t normal. An iceberg that big has never broken off Larson C before. 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 lost ice? Or is it heading toward a breakup?

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.”

Ice shelves have disappeared before. There used to be an ice shelf called Larson A. It was located to the north of Larson C. In 1995, Larson A suddenly shattered into thousands of icebergs. The same thing happened to Larson B in 2002. Larson B used to be between Larson A and C.

“It was shocking,” says Hulbe. She observed the dramatic break up of Larsen B in images from a spacecraft. “The surface of the ocean looked like a blue slushy,” she says.

Hulbe and her colleagues studied these events. They used 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 and refroze. When water freezes, it expands. This made the cracks worse and weakened the ice.

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

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.”

Antarctica’s ice is melting faster because of climate change. Climate change is the 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 warm Earth’s atmosphere. They’re released by burning fuels like gasoline and coal.

If the Larson C ice shelf crumbles completely, the consequences could be severe. Ice shelves act like plugs. They slow the flow of glaciers into the sea. Without plugs, the ice drains faster.

“These ice shelves are like canaries in a coal mine,” says Eric Rignot. He studies glaciers 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, Rignot predicts more ice shelves will be at risk. That includes ice shelves farther south. These ice shelves are even bigger than Larson C and hold back even bigger glaciers. Ice in West Antarctica covers an area twice the size of Texas. If it vanishes, it will raise the sea level by roughly 10 feet. If that happens, coast around the world would be covered in water.

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