Sep 25, 2017

A key Antarctic glacier just lost a huge piece of ice — the latest sign of its worrying retreat

Pine Island Glacier
Antarctica
by
Chris Mooney
,
Washington Post
The Pine Island Glacier calves 100 square miles of ice. Image: Stef Lhermitte
The Pine Island Glacier calves 100 square miles of ice. Image: Stef Lhermitte

An enormous Antarctic glacier has given up an iceberg over 100 square miles in size, the second time in two years it has lost such a large piece in a process that has scientists wondering whether its behavior is changing for the worse.

The Pine Island Glacier is one of the largest in West Antarctica, a region that is currently Antarctica’s biggest ice loser. Pine Island, which loses an extraordinary 45 billion tons of ice to the ocean each year — equivalent to 1 millimeter of global sea level rise every eight years — is 25 miles wide where its floating front touches the sea, and rests on the seafloor in waters more than a half-mile deep. The single glacier alone contains 1.7 feet of potential global sea level rise and is thought to be in a process of unstable, ongoing retreat.

That’s why scientists are watching it closely, and on Saturday, Stef Lhermitte, a satellite observation specialist at Delft University of Technology in the Netherlands, posted a satellite image showing that Pine Island had “calved,” or broken off a piece of ice about 103 square miles in area. (For comparison, Manhattan is 22.83 square miles in size.) The rectangular piece of ice then appears to have lost some of its shape immediately as smaller pieces splintered off.

“It’s the fifth large calving event since 2000,” Lhermitte said. “This one and 2015, they were much further inland than the previous ones. So there has been a retreat of the calving front, specifically between 2011 and 2015.”