理工类：阅读理解 Arctic Melt
Earths North and South Poles are famous for being cold and icy. Last year， however， the amount of ice in the Arctic Ocean fell to a record low1.
Normally， ice builds in Arctic waters around the North Pole each winter and shrinks during the summer. But for many years， the amount of ice left by the end of summer has been declining.
Since 1979， each decade has seen an 11.4 percent drop in end-of-summer ice cover2. Between 1981 and 2000， ice in the Arctic lost 22 percent of its thickness —— becoming 1.13 meters thinner.
Last summer， Arctic sea ice reached its skimpiest levels yet. By the end of summer 2007， the ice had shrunk to cover just 4.2 million square kilometers. Thats 38 percent less area than the average cover at that time of year. Andits a very large 23 percent below the previous record low， which was set just 2 years ago. This continuing trend has scientists concerned
There may be several reasons for the ice melt， says Jinlun Zhang， an oceanographer at the University of Washington3 in Seattle. Unusually strong winds blew through the Arctic last summer. The winds pushed much of the ice out of the central Arctic， leaving a large area of thin ice and open water4.
Scientists also suspect that fewer clouds cover the Arctic now than in the past. Clearer skies allow more sunlight to reach the ocean. The extra heat warms both the water and the atmosphere. In parts of the Arctic Ocean last year， surface temperatures were 3.5℃Celsius warmer than average and 1.5℃ warmer than the previous record high5.
With both air and water getting warmer， the ice is melting from both above and below. In some parts of the Beaufort Sea6， north of Alaska and western Canada， ice that measured 3.3m thick at the beginning of the summer measured just 50 centimeters by seasons end.
The new measurements suggest that melting is far more severe than scientists have seen by just looking at ice cover from above， says Donald K. Perovich， a geophysicist at the U. S. Army Cold Regions Research and Engineering Laboratory in Hanover， N.H.7
Some scientists fear that the Arctic is stuck in a warming trend from which it may never recover.
词汇：
Arctic n.北极，北极圈；adj.北极的
the Arctic Ocean 北冰洋 shrink v.萎缩；缩小，减少 oceanographer n.海洋学家 skimpy adj.缺乏的，不足的 centimeter n.厘米 geophysicist n.地球物理学家
注释：
1. fell to a record low： 跌到历史最低点。record 作形容词时，意思是“空前的，创记 录的”。Record low 的反义词是 record high： 历史最高点。
2. ice cover： 冰覆盖量
3. University of Washington： 华盛顿大学，创建于 l861 年，座落在美国华盛顿州西雅图 市东北角，所以又称西雅图华盛顿大学，是美国著名的公立研究型大学。
4. open water： 没有冰覆盖的海面
5. record high ： 见注释1.
6. the Beaufort Sea： 波弗特海，是北冰洋边缘海，位于美国阿拉斯加州东北岸和加拿大 西北岸，海中岛屿稀少，有无岛海之称。
7. Hanover，N.H：新罕布什尔州汉诺威市。N.H.是 New Hampshire 的缩写。该州位于美 国新英格兰地区。