There Goes Antarctica

There’s nothing like another dramatic effect of global warming to make you think, gee, this whole climate change thing looks like it’s going to be more problematic than a few extra balmy days in March. And while Hurricane Katrina, vanishing glaciers, the current drought in the American southwest and the floods in Missouri last week all have their partisans as far as uh-oh moments go, there’s nothing like the collapse of an Antarctic ice shelf to demonstrate the catastrophic—as opposed to gradual—effects of climate change.

This week’s exhibit A: a hunk of an Antarctic ice shelf larger than the state of Connecticut is collapsing into the sea.

We have been this way before. In 2002, part of the Larsen B ice shelf, which had been floating on the eastern side of the Antarctic Peninsula, broke off from the continent and gave birth to an armada of thousands of icebergs in the Weddell Sea. It took all of 35 days for an area of the ice shelf measuring 3,250 square kilometers (larger than Rhode Island) to disintegrate, starting on January 31 of that year. Other ice shelves that have collapsed recently: the Prince Gustav Channel, Larsen Inlet, Larsen A, Wordie, Muller, and the Jones.

Now the Wilkins Ice Shelf, also on the Antarctic Peninsula and about 1,000 miles south of the tip of South America, is following suit, as captured in a series of satellite images.

“Wilkins is the largest ice shelf on the Antarctic Peninsula yet to be threatened,” David Vaughan of the British Antarctic Survey said in a statement. “I didn’t expect to see things happen this quickly. We predicted it would happen, but it’s happened twice as fast as we predicted.”

Ice shelves are permanent (hah) floating slabs that jut out from land. Because they bob atop the sea, when they melt they do not raise sea levels, as ice melting from solid land do. (When the ice cubes in your gin and tonic melt, the level of the drink does not rise.)

But the collapse of an ice shelf is yet another sign of precipitous climate change.

The Antarctic Peninsula is one of the fastest-warming regions on Earth. Although other regions of the frozen continent have cooled in recent decades, the Peninsula has warmed by 8 degrees F. in the last century, or 0.9 degree F. per decade—faster than it has in the last 2,000 years and several times more than the global average. Ice shelves can’t tolerate that rise in the mercury any better than Frosty the Snowman can, and as a result 13,680 square kilometers (5,282 square miles) of the Wilkins is on the verge of collapse.

“We believe the Wilkins has been in place for at least a few hundred years,” said Ted Scambos of the National Snow and Ice Data Center said in a statement. “But warm air and exposure to ocean waves are causing a break-up."

According to satellite images, the Wilkins began to crack up on February 28, when an iceberg measuring 25.5 by 1.5 miles broke off from its southwestern front, triggering what the NSIDC calls “a runaway disintegration” of 220 square miles of the shelf interior. As the edge of the shelf crumbled, it exposed sky-blue deep glacial ice. Now the rest of the shelf is hanging on by a 3.7-mile thread.

Although collapsed ice shelves do not raise sea levels directly, they may do so indirectly. Many shelves act like corks in a bottle. The wine is a glacier. Without an ice shelf to hold it back, a land-based glacier can flow to the sea unimpeded. That does add to the volume of water in the world's oceans, causing the waves to creep onshore a little more with every passing year.