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  3. For years, the leading theory for what caused the Younger Dryas (a dramatic

For years, the leading theory for what caused the Younger Dryas (a dramatic

游客2025-02-19  34
问题     For years, the leading theory for what caused the Younger Dryas (a dramatic reversal, about 12,900 years ago, in a global warming trend) was a release of water from Glacial Lake Agassiz. The theory posited that this meltwater flooded into the North Atlantic, lowering the salinity and intensity of surface waters enough to prevent them from sinking. Ocean currents were changed in such a way that northward transport of heat in the ocean diminished, and the North Atlantic regions plunged back into near-glacial conditions. However, evidence has emerged that the Younger Dryas began long before freshwater flooded the North Atlantic. Additionally, the temperature changes included by a shutdown in the North Atlantic heat conveyor system are too small to explain the Younger Dryas. [br] The author of the passage implies which of the following about the release of water from glacial Lake Agassiz?
选项 A、The notion that the release occurred has been challenged by more recent findings.
B、The release probably occurred much earlier than scientists have generally assumed.
C、The release would not have been sufficient to cause any temperature change in the North Atlantic.
D、The timing of the release is such that it probably did not trigger the onset of the Younger Dryas.
E、The release was probably unrelated to the global warming trend that was taking place.
答案 D
解析 本题问作者观点，因此定位点是第四句及之后。选项D对应第四句，新仙女木期的发生早于淡水的涌入，因此水的释放时间有可能不能引发新仙女木期的开始。A项水的释放是事实，并没有被质疑，被质疑的是水的释放同新仙女本期之间的关系。B项老观点认为水的释放可以导致新仙女木期，而新仙女木期的时间是确定的，在12900年前。因此科学家普遍认为水的释放时间是在新仙女木期之前，而作者认为新仙女木期的开始早于水的释放，因此作者认为水的释放时间在新仙女木期之后，所以水的释放时间应该晚于科学家普遍认为的。C项太极端。E项文章看不出来水的释放和全球变暖的关系。
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