A
A tiny clue found in ancient deposits has unlocked big secrets about Greenland’s past and future climate. Just beyond the northwest edge of the vast Greenland Ice Sheet, researchers have discovered lake mud that have survived the last ice age. The mud, and remains of common flies in it, record two interglacial periods (间冰期) in northwest Greenland.
Although researchers have long known these two periods—the early Holocene and Last Interglacial—experienced warming in the Arctic, the mix of fly species shows that Greenland was even warmer than previously thought. “As far as we know, it has never been found in Greenland. We think this is the first time anyone has reported it in ancient deposits or modern lakes there, ” Axford said. “We were really surprised to see how far north it migrated (迁徙). ”
This new information could help researchers better measure Greenland’s sensitivity to warming, by testing and improving models of climate and ice sheet behaviour. Those models could then improve predictions of how Greenland’s ice sheet might respond to man-made global warming. After all, Greenland covers 80 per cent of the Arctic country and holds enough ice to equal 20 feet of global sea level. “Northwest Greenland might feel really remote, but what happens to that ice sheet is going to matter to everyone in every coastal city around the world, ” said Yarrow Axford, an associate professor in the team. “One of the big uncertainties in climate science is how fast the Earth changes when it gets warmer. Geology gives us an opportunity to see what happened when the Earth was warmer than today, ” said Axford.
People might be surprised to see how today’s Greenland looked during the last two interglacial periods. During the Last Interglacial, global sea levels increased by 15 to 30 feet, largely due to thinning of Greenland and Antarctica’s ice sheets. However, now researchers believe northern Greenland’s ice sheet experienced stronger warming than previously thought, which could mean that Greenland is more responsible for that sea-level rise.
Finding lake deposits older than about 10, 000 years, however, has been historically very difficult in Greenland. To measure these ancient temperatures, researchers look to ice cores (冰核) and lake deposits. Since ice and lake deposits form by a gradual buildup on annual layers of snow or mud, these cores contain history of the past. By looking through the layers, researchers can obtain climate clues from centuries ago.
【文章大意】本文为一篇说明文, 文章主要介绍了研究人员在格陵兰冰原的西北边缘发现了在最后一个冰河时代幸存下来的湖泥, 这些淤泥和常见苍蝇的遗骸表明, 格陵兰北部的冰盖经历了比之前认为的更强烈的变暖, 以及阐明这一研究背后的意义。
1. Why are the remains of flies mentioned in the first two paragraphs?
A. They serve as evidence that there is still life in the Northwest Greenland.
B. They were one of the many ancient lives that were left in the Greenland mud.
C. They are indicators that Greenland was much warmer than previously thought.
D. They help the researchers realize that there was once a warm period in the Arctic.
【解析】选C。推理判断题。根据第一段最后一句 The mud, and remains of common flies in it, record two interglacial periods in northwest Greenland. 和第二段第一句 Although researchers have long known these two periods — the early Holocene and Last Interglacial — experienced warming in the Arctic, the mix of fly species shows that Greenland was even warmer than previously thought. 可知苍蝇种类的混合表明, 格陵兰甚至比以前认为的还要温暖。
2. The new information about Greenland is important because _________.
A. researchers have no idea how to measure Greenland’s warming speed
B. it can help researchers better study Greenland’s response to warming
C. people should be more sensitive to the changes in the ice in Greenland
D. it is uncertain how fast the Earth changes with man-made global warming
【解析】选B。细节理解题。根据第三段第一句This new information could help researchers better measure Greenland’s sensitivity to warming, by testing and improving models of climate and ice sheet behavior. 可知这些新信息可以帮助研究人员更好地测量格陵兰岛对变暖的敏感性。
3. Which of the following can be inferred from the passage?
A. It is easier for today’s scientists to find ancient lake deposits.
B. People are surprised at the landscape feature of Greenland today.
C. Researchers measure the changing temperatures by directly examining mud.
D. Greenland holds enough ice that might one day threaten life in coastal cities.
【解析】选D。 推理判断题。根据第三段After all, Greenland covers 80 per cent of the Arctic country and holds enough ice to equal 20 feet of global sea level. “Northwest Greenland might feel really remote, but what happens to that ice sheet is going to matter to everyone in every coastal city around the world, ” said Yarrow Axford, an associate professor in the team. 可知格陵兰的冰盖变化会影响沿海城市的每一个人。
