Noelle Swan

UD researcher explores potential impact of new ice island breaking off Greenland

In Climate Change on July 25, 2012 at 6:06 pm

This article first was published by DFM News on July 25, 2012.

A floating ice island, twice the size of Manhattan, broke off of Petermann’s Glacier last week. The glacier, a giant ice pack, connects Greenland’s ice sheet to the Arctic Ocean. According to University of Delaware researcher Andreas Muenchow, this most recent event could be literally just the tip of the iceberg, a warning sign that the rate at which the Greenland ice sheet discharges freshwater into the Arctic Ocean is accelerating and potentially driving a global rise in sea level.“This ice island looks dramatic, but the larger story will evolve over 10 years,” says Muenchow, an assistant professor of physical ocean science and engineering.

Muenchow is conducting a multi-year study of freshwater discharge into the Arctic Ocean in collaboration with Canadian researchers and the U.S. and Canadian coast guards. Next week, Muenchow will collect instruments that he hopes lie waiting at the bottom of Nares Strait, where he and his fellow researchers deposited them in 2009 to record basic information about salinity, temperature, currents, and pressure. In 2010, another giant ice island, this one four times the size of Manhattan, broke off in the same area of Petermann’s Glacier. This 2010 ice island purportedly floated directly above these instruments which could be a blessing or a curse; his instruments could either be ruined or contain bonus data about the passing ice island.

When he heard about the new ice island last week, Muenchow downloaded the raw data from a NASA database and processed the imagery. As the world started to ask questions about the Arctic Ocean’s newest ice island, his Canadian colleagues found themselves tangled in a controversial gag order requiring all Canadian scientists to sift through red tape before speaking with the press and leaving the UD professor to field the press.

Most Americans are familiar with the photos of Alaska’s majestic cliff glacier formations, which tower above the sea, routinely shedding chunks of ice into Glacier Bay, Muenchow explains. However, this latest ice island broke away from a different kind of glacier, a sheet of ice that stretches out flat and thin across the surface of the ocean, closer to the frozen surface of a pond than a solid mountain of ice. At 656,000 square miles, the Greenland ice sheet is the second largest expanse of ice in the world, second only to the Arctic ice sheet.

Glaciers flow continuously. Their speed is well … glacial, so humans can’t see it happening. The effects are visible, however, as pieces of ice continually break off into the sea in a process known as “calving.” Muenchow worries that the combined girth of the 2010 and 2012 calvings could signal major changes in the overall ice sheet.

“Breaking off is perfectly normal to us in a state where nothing is changing. That’s happening all around Antarctica. Because these masses of ice are so huge and they reflect what is happening all over Greenland in some way, they have an impact.”

Researchers may not fully understand that impact for years to come, Muenchow adds. While chunks of ice that tumble from cliffs and splash in the waters below add volume to the sea and immediately affect sea level, Greenland’s ice sheet adds volume continually as it expands and the edges melt into the sea. Melt-off accounts for far more glacier loss than even ice islands of this size. While some melt-off is typical every summer, NASA satellite imagery released this week indicates that this month melt-off has reached unprecedented levels.

The size of this ice island and the one that broke off in 2010, the likes of which Muenchow says have not been observed in the last 100 to 150 years, raise additional concerns. A delicate balance keeps a glacier glued to the layer of bedrock below. Ice, rock, and sea meet at what is called the hinge line. In Antarctica, researchers have seen hinge lines move over time, resulting in a thinner, potentially less stable ice sheet behind it. “We don’t know what it takes to move that hinge line. Nobody knows,” Muenchow says, adding that in general the physics are poorly understood.

The advent of these giant ice islands combined with rapid melting have left researchers scrambling to understand what this means for global climate. Greenland has been long considered a canary in the coal mine for global climate change. Only time will tell how drastic changes seen this summer affect the rest of the world.

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