VOA标准英语2013--Warm Ocean Accelerating Antarctic Ice Loss

 

Warm Ocean Accelerating Antarctic Ice Loss

The study is the first comprehensive survey of all the Antarctic ice shelves, which are the 1.5 million square kilometers that fringe much of the frozen continent. 

Lead author Eric Rignot, a professor at the University of California, Irvine, says ice melt from below accounted for 55 percent of the shelf loss from 2003 to 2008, a rate much higher than previously¹ thought.   

“We find that the melting of the underside of the ice shelves is even larger than the production of icebergs," Rignot said. "So it is the dominant² process of ice removal in the Antarctic.”  

Rignot and colleagues used satellite observations, radar³ and computer models to measure features above the ice to calculate what was going on below.  

“That includes the velocity⁴ of the ice, the thickness of the ice, how fast the freeboard [height of ice above sea level] of the ice shelf is changing with time and also how much snowfall there is on the top of the ice shelves,” Rignot said.

The measurements showed regional differences around the continent. The giant ice shelves - Ross, Filchner and Ronne - make up two-thirds of Antarctica’s ice shelves, yet accounted for only 15 percent of the melting.

Meanwhile, a dozen small ice shelves, which sit on relatively⁵ warmer water, produced half the total water from ice melt during the same period.                                                                                                                                                                                                                                                                                           

 “That means that in a regime of climate warming where the properties of the Southern Ocean are changing, they may be changing faster than other oceans in the world," Rignot said. "We may be in a situation where the coastline of Antarctica may be changing at a faster pace than we thought in the past.”  

The ocean is a very sensitive system, according to Rignot, and even small shifts, like changes in ocean circulation driven by wind, can make a huge difference in ice shelf melt.

“If the wind regime changes in the Southern Ocean, it is going to change the way the ocean heat is distributed on the coast, and that’s going to affect glaciers,” he said.

Sixty percent of the planet’s fresh water is locked in the massive Antarctic ice sheet. Rignot says the study will help scientists predict how the continent responds to a warmer ocean and contributes to global sea level rise.  

“I think that it places more emphasis on the enormous importance of ice-ocean interaction in the Antarctic," he said. "If we really want to understand how these ice shelves evolve and will evolve in the future we must understand how the ocean is contributing to their melting in the underside.” 

1 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

2 dominant   

adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因

参考例句：

• The British were formerly dominant in India.英国人从前统治印度。
• She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。

3 radar   

n.雷达，无线电探测器

参考例句：

• They are following the flight of an aircraft by radar.他们正在用雷达追踪一架飞机的飞行。
• Enemy ships were detected on the radar.敌舰的影像已显现在雷达上。

4 velocity   

n.速度，速率

参考例句：

• Einstein's theory links energy with mass and velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。
• The velocity of light is about 300000 kilometres per second.光速约为每秒300000公里。

5 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。