南极冰层原来也可由下往上形成(有声)
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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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Antarctic Ice Sheets Grow From Bottom Up, Scientists Discover
When it comes to ice, scientists are giving a whole new meaning to the phrase "bottoms up." Those massive ice sheets in Antarctica don't just grow on top when snow falls, they also grow from the bottom up, according to new research published Thursday.
当讨论到冰这个现象的时候，科学家们现在给出了一个全新的短语“bottoms up"即从底部往上，即冰层形成原来也可由下往上累积起来～
根据周四发布的最新调查研究，南极巨大的冰层不止是由上面的积雪形成，它们也从下往上形成。
【拓展阅读】
南极冰层最初是怎样形成的？
南极冰层首次形成的方式（当时是距今大约3400万年前的一个全球气候迅速变化的时期）一直是一个有相当大猜测性的问题。来自几个方面的证据都表明，南极中部山系是最初冰层的所在地点，但我们关于当前冰层地貌的知识高度局限在冰层最初形成最可能发生的区域：位于当前冰层中心、沿冰川下的 Gamburtsev山系的地方。现在，研究人员根据在两个季节中所进行的一项能够穿透冰层的雷达研究，完成了对Gamburtsev山系形态的详细勘查和分析。所获数据显示了一个最初被河流切割、然后又被冰的运动加深的山地景观。深至冰层下3000米的地貌像是经典高山峡谷地貌发生爆炸后的版本，似乎是在距今3400万年前形成的，当时的平均夏季气温约为3摄氏度。
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