Ice calving occurs when a large piece of ice breaks off another large piece of ice, often due to melting at the waterline. (Paul Souders / Corbis)
Breaking the Ice
A massive iceberg breaks away as Greenland experiences its biggest ice melt in 30 years
PHOTO: More than 80 percent of Greenland is covered in ice. (James Balog / Aurora Photos / Corbis)
MAP: The Petermann Glacier is one of Greenland’s largest glaciers. (Jim McMahon)
In just four days last month, the surface of Greenland’s ice cover melted more than it has in the past 30 years. Nearly all of Greenland’s ice sheet experienced some level of melting, according to NASA, the U.S. space agency, which reviewed images of Greenland taken from outer space.
The melting spread quickly. From July 8 to 12, it expanded from 40 percent of the ice sheet’s surface to 97 percent. Usually, only about half of Greenland’s ice cover melts during the entire summer.
Scientists say the melt happened at the same time that an unusually strong ridge of warm air, called a heat dome, passed over Greenland. Several of these heat domes have occurred there since May.
Also in July, an iceberg measuring 46 square miles—twice the size of Manhattan—broke off the Petermann Glacier, one of Greenland’s largest glaciers. That same glacier produced an even bigger iceberg, four times the size of Manhattan, two years ago. Ice calving (breaking) of this extent normally happens only every 10 to 20 years.
CLIMATE-CHANGE CLUES
Both of these events have grabbed the attention of scientists. More than 80 percent of Greenland—an island in northern North America and a territory of Denmark—is covered in ice. But that ice sheet is getting smaller.
Andreas Muenchow, a professor of oceanography at the University of Delaware, says that northwest Greenland and northern Canada are warming five times faster than the rest of the world. Temperatures in those places have gone up by about 4 degrees Fahrenheit over the past 30 years.
“The Greenland ice sheet as a whole is shrinking, melting, and reducing in size as the result of globally changing air and ocean temperatures and . . . changes in circulation patterns in both the ocean and the atmosphere,” Muenchow says.
Meltwater typically refreezes in place, but near the coast some of it is lost to the ocean. Because there is more melting this year than normal, scientists worry that more meltwater will flow back into the ocean instead of refreezing. The scientists are conducting research to determine how the massive melting might affect climate systems around the world.
“Melting events of this type occur about once every 150 years. With the last one happening in 1889, this event is right on time,” says Lora Koenig, a physical scientist at NASA. “But if we continue to observe melting events like this in upcoming years, it will be worrisome.”
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