炎热的夏季可能放缓冰川的移动
文章来源:未知 文章作者:enread 发布时间:2011-01-27 03:35 字体: [ ]  进入论坛
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Hotter summers may not be as catastrophic for the Greenland ice sheet as previously1 feared and may actually slow down the flow of glaciers3, according to new research. A letter published in Nature on 27 January explains how increased melting in warmer years causes the internal drainage(内部排水) system of the ice sheet to 'adapt' and accommodate more melt-water, without speeding up the flow of ice toward the oceans. The findings have important implications for future assessments4 of global sea level rise.

The Greenland ice sheet covers roughly 80% of the surface of the island and contains enough water to raise sea levels by 7 metres if it were to melt completely. Rising temperatures in the Arctic in recent years have caused the ice sheet to shrink, prompting fears that it may be close to a 'tipping point' of no return.

Some of the ice loss has been attributed to the speed-up of glaciers due to increased surface melting. Each summer, warmer temperatures cause ice at the surface of the sheet to melt. This water then runs down a series of channels to the base of the glacier2 where it acts as a lubricant(润滑油) , allowing the ice sheet to flow rapidly across the bedrock toward the sea.

Summertime acceleration5 of ice flow has proved difficult for scientists to model, leading to uncertainties6 in projections7 of future sea level rise.

"It had been thought that more surface melting would cause the ice sheet to speed up and retreat faster, but our study suggests that the opposite could in fact be true," said Professor Andrew Shepherd from the University of Leeds School of Earth and Environment, who led the study.

"If that's the case, increases in surface melting expected over the 21st century may have no affect on the rate of ice loss through flow. However, this doesn't mean that the ice sheet is safe from climate change, because the impact of ocean-driven melting remains8 uncertain."

The researchers used satellite observations of six landlocked(为陆地所包围的) glaciers in south-west Greenland, acquired by the European Space Agency, to study how ice flow develops in years of markedly different melting.

Although the initial speed-up of ice was similar in all years, slowdown occurred sooner in the warmest ones. The authors suggest that in these years the abundance of melt-water triggers an early switch in the plumbing9(水管设施) at the base of the ice, causing a pressure drop that leads to reduced ice speeds.

This behaviour is similar to that of mountain glaciers, where the summertime speed-up of ice reduces once melt-water can drain(排水) efficiently10.



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1 previously bkzzzC     
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 glacier YeQzw     
n.冰川,冰河
参考例句:
  • The glacier calved a large iceberg.冰河崩解而形成一个大冰山。
  • The upper surface of glacier is riven by crevasses.冰川的上表面已裂成冰隙。
3 glaciers e815ddf266946d55974cdc5579cbd89b     
冰河,冰川( glacier的名词复数 )
参考例句:
  • Glaciers gouged out valleys from the hills. 冰川把丘陵地带冲出一条条山谷。
  • It has ice and snow glaciers, rainforests and beautiful mountains. 既有冰川,又有雨林和秀丽的山峰。 来自英语晨读30分(高一)
4 assessments 7d0657785d6e5832f8576c61c78262ef     
n.评估( assessment的名词复数 );评价;(应偿付金额的)估定;(为征税对财产所作的)估价
参考例句:
  • He was shrewd in his personal assessments. 他总能对人作出精明的评价。 来自《简明英汉词典》
  • Surveys show about two-thirds use such assessments, while half employ personality tests. 调查表明,约有三分之二的公司采用了这种测评;而一半的公司则采用工作人员个人品质测试。 来自百科语句
5 acceleration ff8ya     
n.加速,加速度
参考例句:
  • All spacemen must be able to bear acceleration.所有太空人都应能承受加速度。
  • He has also called for an acceleration of political reforms.他同时呼吁加快政治改革的步伐。
6 uncertainties 40ee42d4a978cba8d720415c7afff06a     
无把握( uncertainty的名词复数 ); 不确定; 变化不定; 无把握、不确定的事物
参考例句:
  • One of the uncertainties of military duty is that you never know when you might suddenly get posted away. 任军职不稳定的因素之一是你永远不知道什么时候会突然被派往它处。
  • Uncertainties affecting peace and development are on the rise. 影响和平与发展的不确定因素在增加。 来自汉英非文学 - 十六大报告
7 projections 7275a1e8ba6325ecfc03ebb61a4b9192     
预测( projection的名词复数 ); 投影; 投掷; 突起物
参考例句:
  • Their sales projections are a total thumbsuck. 他们的销售量预测纯属估计。
  • The council has revised its projections of funding requirements upwards. 地方议会调高了对资金需求的预测。
8 remains 1kMzTy     
n.剩余物,残留物;遗体,遗迹
参考例句:
  • He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
  • The remains of the meal were fed to the dog.残羹剩饭喂狗了。
9 plumbing klaz0A     
n.水管装置;水暖工的工作;管道工程v.用铅锤测量(plumb的现在分词);探究
参考例句:
  • She spent her life plumbing the mysteries of the human psyche. 她毕生探索人类心灵的奥秘。
  • They're going to have to put in new plumbing. 他们将需要安装新的水管。 来自《简明英汉词典》
10 efficiently ZuTzXQ     
adv.高效率地,有能力地
参考例句:
  • The worker oils the machine to operate it more efficiently.工人给机器上油以使机器运转更有效。
  • Local authorities have to learn to allocate resources efficiently.地方政府必须学会有效地分配资源。
TAG标签: water ice glaciers
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