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The mystery of the expansion of sea ice around Antarctica, at the same time as global warming is melting swaths of Arctic sea ic

admin2015-09-26  56
问题     The mystery of the expansion of sea ice around Antarctica, at the same time as global warming is melting swaths of Arctic sea ice, has been solved using data from U. S. military satellites.
    Two decades of measurements show that changing wind patterns around Antarctica have caused a small increase in sea ice, the result of cold winds off the continent blowing ice away from the coastline.
    "Until now these changes in ice drift were only speculated upon using computer models," said Paul Holland at the British Antarctic Survey. "Our study of direct satellite observations shows the complexity of climate change. "
    "The Arctic is losing sea ice five times faster than the Antarctic is gaining it, so, on average, the Earth is losing sea ice very quickly. There is no inconsistency between our results and global warming. "
    The extent of sea ice is of global importance because the bright ice reflects sunlight far more than the ocean, meaning temperature rises still further.
    This summer saw a record low in Arctic sea ice since satellite measurements began 30 years ago. Holland said the changing pattern of sea ice at both poles would also affect global ocean circulation, with unknown effects. He noted that while Antarctic sea ice was growing, the Antarctic ice cap—the glacier and snow pack on the continent—was losing mass, with the fresh water flowing into the ocean.
    The research on Antarctic sea ice, published in Nature Geoscience, revealed large regional variations. In places where warm winds blowing from the tropics towards Antarctica had become stronger, sea ice was being lost rapidly. "In some areas, such as the Bellingshausen Sea, the sea ice is being lost as fast as in the Arctic," said Holland.
    But in other areas, sea ice was being added as sea water left behind ice being blown away from the coast froze. The net effect is that there has been an extra 17, 000 sq km of sea ice each year since 1978—about a tenth of a percent of the maximum sea ice cover.
    Antarctica is a continent surrounded by an ocean, whereas the Arctic is an ocean surrounded by a continent. For that reason, said Holland, sea ice was not able to expand by the same mechanism in the Arctic as at the southern pole, because if winds pushed the ice away from the pole it quickly hit land.
    Holland did the research with Ron Kwok at Nasa’s jet propulsion laboratory in California, where maps of sea ice movements were created from more than 5m individual daily measurements collected over 19 years. The maps showed, for the first time, the long-term changes in sea ice drift around Antarctica.
    Kwok said: "The Antarctic sea ice cover interacts with the global climate system very differently than that of the Arctic, and these results highlight the sensitivity of the Antarctic ice coverage to changes in the strength of the winds around the continent. "  
According to what Holland said, we can draw the conclusion that______.
选项 A、we can rely on satellite to estimate changes in ice drift
B、his research results conflict with global warming
C、the location of Bellingshausen Sea is around the Antarctic
D、the Antarctic ice coverage is sensitive to changes in wind strength
答案C
解析 推理题。文章第七段最后一句提到，霍兰德说在某些地方海冰减少的速度和北极一样快，并以别林斯高晋海为例，再根据上一句可知，这些地方是位于南极，在这里从热带地区吹来的暖风变得更强了，所以海冰正在迅速减少，由此推出[C]“别林斯高晋海的位置在南极周围”为正确答案。第三段第一句霍兰德提到这些浮冰的变化只能依靠计算机模型来推测，所以[A]“我们可以依靠卫星来推测浮冰的变化”与文意不符，故排除；第四段最后霍兰德提到，我们的研究结果和全球变暖并无相矛盾之处，因此[B]“他的研究结果与全球变暖相矛盾”与文意相反，故排除；文章的最后一段提到，这些结果突出强调了南极冰盖对南极周围风力变化的灵敏度，但这是罗恩·郭所说的话，故排除[D]。
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