500万年全球曾变暖使海平面上升
文章来源:未知 文章作者:enread 发布时间:2013-07-22 06:34 字体: [ ]  进入论坛
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Global warming five million years ago may have caused parts of Antarctica's large ice sheets to melt and sea levels to rise by approximately 20 metres, scientists report today in the journal Nature Geoscience. The researchers, from Imperial College London, and their academic partners studied mud samples to learn about ancient melting of the East Antarctic ice sheet. They discovered that melting took place repeatedly between five and three million years ago, during a geological period called Pliocene Epoch1, which may have caused sea levels to rise approximately ten metres.
 
Scientists have previously2 known that the ice sheets of West Antarctica and Greenland partially3 melted around the same time. The team say that this may have caused sea levels to rise by a total of 20 metres.
 
The academics say understanding this glacial melting during the Pliocene Epoch may give us insights into how sea levels could rise as a consequence of current global warming. This is because the Pliocene Epoch had carbon dioxide concentrations similar to now and global temperatures comparable to those predicted for the end of this century.
 
Dr Tina Van De Flierdt, co-author from the Department of Earth Science and Engineering at Imperial College London, says: "The Pliocene Epoch had temperatures that were two or three degrees higher than today and similar atmospheric4 carbon dioxide levels to today. Our study underlines that these conditions have led to a large loss of ice and significant rises in global sea level in the past. Scientists predict that global temperatures of a similar level may be reached by the end of this century, so it is very important for us to understand what the possible consequences might be."
 
The East Antarctic ice sheet is the largest ice mass on Earth, roughly the size of Australia. The ice sheet has fluctuated in size since its formation 34 million years ago, but scientists have previously assumed that it had stabilised around 14 million years ago.
 
The team in today's study were able to determine that the ice sheet had partially melted during this "stable" period by analysing the chemical content of mud in sediments5. These were drilled from depths of more than three kilometres below sea level off the coast of Antarctica.
 
Analysing the mud revealed a chemical fingerprint7 that enabled the team to trace where it came from on the continent. They discovered that the mud originated from rocks that are currently hidden under the ice sheet. The only way that significant amounts of this mud could have been deposited as sediment6 in the sea would be if the ice sheet had retreated inland and eroded8 these rocks, say the team.


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1 epoch riTzw     
n.(新)时代;历元
参考例句:
  • The epoch of revolution creates great figures.革命时代造就伟大的人物。
  • We're at the end of the historical epoch,and at the dawn of another.我们正处在一个历史时代的末期,另一个历史时代的开端。
2 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。
3 partially yL7xm     
adv.部分地,从某些方面讲
参考例句:
  • The door was partially concealed by the drapes.门有一部分被门帘遮住了。
  • The police managed to restore calm and the curfew was partially lifted.警方设法恢复了平静,宵禁部分解除。
4 atmospheric 6eayR     
adj.大气的,空气的;大气层的;大气所引起的
参考例句:
  • Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
  • Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。
5 sediments 8b3acb612b624abdf2c2881bc6928565     
沉淀物( sediment的名词复数 ); 沉积物
参考例句:
  • When deposited, 70-80% of the volume of muddy sediments may be water. 泥质沉积物沉积后,体积的70-80%是水。
  • Oligocene erosion had truncated the sediments draped over the dome. 覆盖于穹丘上的沉积岩为渐新世侵蚀所截削。
6 sediment IsByK     
n.沉淀,沉渣,沉积(物)
参考例句:
  • The sediment settled and the water was clear.杂质沉淀后,水变清了。
  • Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。
7 fingerprint 4kXxX     
n.指纹;vt.取...的指纹
参考例句:
  • The fingerprint expert was asked to testify at the trial.指纹专家应邀出庭作证。
  • The court heard evidence from a fingerprint expert.法院听取了指纹专家的证词。
8 eroded f1d64e7cb6e68a5e1444e173c24e672e     
adj. 被侵蚀的,有蚀痕的 动词erode的过去式和过去分词形式
参考例句:
  • The cliff face has been steadily eroded by the sea. 峭壁表面逐渐被海水侵蚀。
  • The stream eroded a channel in the solid rock. 小溪在硬石中侵蚀成一条水道。
TAG标签: sea global ice
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