南极冰层原来也可由下往上形成

The ice surface of Antarctica, looking toward the Gamburtsev Mountains and Dome A. Deep below the surface here, new ice is forming around the mountains and pushing upward. The black flags in the distance mark the edge of the runway for research aircraft studying the area.

STEVE INSKEEP, host:You are listening to a news network that works to get below the surface of the story, and that's what we're about to do with the ice in Antarctica.

You can think of that continent as an amazing layer cake made from millions of layers of snow that fall over many, many years and gradually turn to ice. But scientists are coming to realize that is not the whole story. A new study finds that some of the ice in Antarctica is actually forming from underneath the glaciers, instead of being piled on from the top.

Here's NPR's Richard Harris.

RICHARD HARRIS: This surprising discovery stems from a research blitz to Antarctica a few years back. Robin Bell, from the Lamont Doherty Earth Observatory, was part of the scientific gold-rush called the International Polar Year.

Dr. ROBIN BELL (Senior Research Scientist, Lamont Doherty Earth Observatory): We went to the middle of East Antarctica, because this was the last unexplored mountain range on our planet.

HARRIS: This is actually a mountain range of rock, buried under up to two miles of solid ice. They flew over this area with airplanes equipped with lasers, radars and other sensors that allowed them to peer through the ice to the rock that lay far below.

Dr. BELL: First, we were just surprised at how rough the mountains were underneath.

HARRIS: Lots of the bedrock in Antarctica is flat and boring, but certainly not here. And as Bell took a close look at her radar images of the ice piled high at top the mountains, she noticed some extraordinary strange features: blobs that she describes as beehives, or maybe jelly-donuts.

Dr. BELL: Turned out that these big blobs underneath the ice sheet were ice that had frozen on from the bottom of the ice sheet, that there was water moving around underneath the ice sheet and it had frozen back onto the bottom of the ice sheet.

HARRIS: Ice in Antarctica isn't supposed to form that way. It's supposed to fall from the sky as snow, and then form from the top down. But here, Bell saw unusual ice structures, thousands of feet thick in places. Heat from the Earth had melted the bottom of these glaciers, and then that water refroze. And it created what you could think of as gigantic frost heaves, so powerful that they actually altered the shape of the surface, miles up.

Bell says scientists have known for over a decade that liquid water forms under Antarctica, and that it flows from one place to another.

Dr. BELL: But now this is actually showing that the (unintelligible adj.莫名其妙的，无法理解的) water can actually change the overlying ice sheet.

HARRIS: That discovery is published online by Science magazine. It changes the way scientists think about the processes that shape Antarctica. And Bell says it could also complicate plans to study the Earth's past climate. That's because scientists drill down through the layers of ice to study the air bubbles from ancient air that's trapped inside the ice.

Dr. BELL: You think of each layer in the ice sheet being a history book and telling us what was going on the planet at that time.

HARRIS: But that record is destroyed when the ice melts and refreezes, as Bell has found along this mountain crest.

Dr. BELL: Unfortunately, these books have been erased.

HARRIS: That's not a disaster. Kendrick Taylor, at the Desert Research Institute in Reno, Nevada（内华达州）, notes that there have already been several amazing ice-cores taken from Antarctica.

Professor KENDRICK TAYLOR (Desert Research Institute, Nevada): We currently have records of greenhouse gases that go back to about 800,000 years. And we would like to extend that record further back in time, so we can see how changes in greenhouse gases influenced climate for, oh, say the last 1.5 million years.

HARRIS: But as fate would have it, that super-long record is most likely to be found in the exact mountain range where Robin Bell has now discovered ice melting and reforming from below. Taylor says several research teams, including one from China and another from the U.S., have been interested in drilling there, despite the considerable challenges.

Prof. TAYLOR: It's almost like working on another planet out there.

HARRIS: Chinese scientists already have a running start. They've staked out a camp along the flank of the mountain, Taylor says.

Prof. TAYLOR: And they have a little of a challenge. If they drill at the logistically convenient spot, which is their camp, they won't be drilling at the optimal spot for the ice core. So how they're going to address that challenge, we really don't know.

HARRIS: The ancient ice record they're searching for may be really hard to find.

Richard Harris, NPR News.

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