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【转帖】造成上新世大范围冰川形成的因素
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biface: 又是模拟，都不知道这些模拟的结果到底有多大可信度？模拟的再完美，一个不起眼的偶然因素可能就会导致全局的改变，不可知啊，不好说... 尽管从气候变化角度讲，冰层稳定性很重要，但我们对控制冰层体积的机制的认识仍有很大空白。北半球被认为在直到晚上新世大规模冰川形成过程开始之前（距今约300万年前）有超过3000万年几乎没有冰层。人们曾提出几个假设来解释当时格陵兰冰层的增长。现在，利用一个完全耦合的大气—海洋环流模型和一个冰层模型所作的一次新的模拟表明，格陵兰冰层在上新世增长的主要驱动因素为大气二氧化碳浓度的下降。其他的假设（巴拿马海洋通道的闭合、厄尔尼诺的终止和构造隆起等）在这一模型中不足以触发大范围的冰川形成。 Late Pliocene Greenland glaciation controlled by a decline in atmospheric CO2 levels Abstracts: Top of pageAbstractIt is thought that the Northern Hemisphere experienced only ephemeral glaciations from the Late Eocene to the Early Pliocene epochs (about 38 to 4 million years ago), and that the onset of extensive glaciations did not occur until about 3 million years ago. Several hypotheses have been proposed to explain this increase in Northern Hemisphere glaciation during the Late Pliocene. Here we use a fully coupled atmosphere–ocean general circulation model and an ice-sheet model to assess the impact of the proposed driving mechanisms for glaciation and the influence of orbital variations on the development of the Greenland ice sheet in particular. We find that Greenland glaciation is mainly controlled by a decrease in atmospheric carbon dioxide during the Late Pliocene. By contrast, our model results suggest that climatic shifts associated with the tectonically driven closure of the Panama seaway, with the termination of a permanent El Niño state or with tectonic uplift10 are not large enough to contribute significantly to the growth of the Greenland ice sheet; moreover, we find that none of these processes acted as a priming mechanism for glacial inception triggered by variations in the Earth's orbit. Nature 454, 1102-1105 (28 August 2008) | doi:10.1038/nature07223 [ Last edited by ewigkeit on 2008-8-29 at 08:57 ] |
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