Antarctica's Ice Sheets Are Melting Faster — And From Beneath

Oct 25, 2016
Originally published on October 25, 2016 6:00 pm

Antarctica's ice has been melting, most likely because of a warming climate. Now, newly published research shows the rate of melting appears to be accelerating.

Antarctica is bigger than the U.S. and Mexico combined, and it's covered in deep ice — more than a mile deep in some places. Most of the ice sits on bedrock, but it slowly flows off the continent's edges. Along the western edge, giant glaciers creep down toward the sea. Where they meet the ocean, they form ice shelves.

The shelves are the specialty of Ala Khazendar, a geophysicist and polar expert at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"You have this floating plate of ice being fed by the glaciers flowing from the interior of the continent," he says, "while having ocean water underneath it." He calls the shelves "the gates of Antarctica."

Although the shelves float, they're still connected to the mainland. The point at which the ice shelf is no longer supported by bedrock is called the "grounding line."

A team from JPL has been studying that grounding line in several places along the edge of the West Antarctic ice sheet. They used radar to look beneath the ice. In particular, overflights have targeted ice shelves along the West Antarctic ice sheet known as the Amundsen Sea Embayment.

They've found that the ice is melting faster than they've ever seen. The researchers believe the cause is warm water circulating beneath the ice shelf. The melting was most pronounced from 2002 to 2009. (The influx of warmer water to the region stalled recently, and the rate of melting seems to have slowed somewhat.)

Khazendar says the more the bottom of the shelves melt, the more ice is exposed to warm water. "It becomes a runaway process," he explains, "which makes it unstable."

Where's the warmer water coming from? The team, whose findings appear in the journal Nature Communications, points to global warming that's heating up the oceans. There's been a spate of research lately showing that Antarctic ice is melting faster than previously thought — and raising global sea levels.

Khazendar says the melting process appears to be irreversible. Polar scientists fear that at some point, the shelves will collapse and Antarctica's glaciers will flow into the sea. As to whether and when that might happen?

"The simple answer is we don't know. And that's the scary part," Khazendar says.

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KELLY MCEVERS, HOST:

Antarctica is bigger than the U.S. and Mexico combined, and it is covered in thick ice. That ice has been melting recently, most probably because of a warming climate. And as NPR's Christopher Joyce reports, the rate of melting appears to be accelerating.

CHRISTOPHER JOYCE, BYLINE: Antarctica's ice is over a mile deep in some parts. It sits on bedrock, but it flows off the continents' edges slowly, especially along the western edge where giant glaciers creep down toward the sea. Where they meet the ocean, they form ice shelves. They are the specialty of Ala Khazander.

ALA KHAZANDER: You have this floating plate of ice being fed by the glaciers flowing from the interior of the continent while having ocean water underneath it.

JOYCE: Khazander is a polar scientist at NASA's Jet Propulsion Laboratory.

KHAZANDER: I like to think of them as the gates of Antarctica.

JOYCE: Although the shelves float, they're still connected to the mainland. A team from JPL has been using radar to see beneath the ice. They found that the ice is melting faster than they've ever seen, especially at the point where the bedrock ends and the ice shelf floats. They believe the cause is warm water circulating beneath the ice shelf. The melting was most pronounced from 2002 to 2009, and Khazander says the more it melts, the more ice is exposed to warm water.

KHAZANDER: It becomes a runaway process, which makes it unstable.

JOYCE: Where's the warmer water coming from? The team points to global warming that's heating up the oceans. And there's been a spate of research lately showing that Antarctic ice is melting faster than previously thought and raising global sea levels. Khazander says the melting process appears to be irreversible. Polar scientists fear that at some point the shelves will collapse, and Antarctica's glaciers will flow into the sea. As to whether and when that might happen...

KHAZANDER: The simple answer is that we don't know, and that's the scary part.

JOYCE: The research appears in the journal Nature Communications. Christopher Joyce, NPR News. Transcript provided by NPR, Copyright NPR.