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摘要 : 人们普遍假设,气候、侵蚀和地质构造之间在地质时间尺度上存在一个反馈,但我们对局部气候对景观侵蚀速度的影响仍然很不了解。

 人们普遍假设,气候、侵蚀和地质构造之间在地质时间尺度上存在一个反馈,但我们对局部气候对景观侵蚀速度的影响仍然很不了解。利用沿夏威夷 “大岛” (Big Island)上跨域一个极端气候梯度的河流在地球化学、岩石力学和侵蚀速度方面的新的景观约束条件,这项研究显示,依赖于气候的化学风化控制河床为基岩的河流的可侵蚀性。虽然这一机制的力度可能会随构造条件、岩石条件和气候条件的不同而不同,但局部降雨与岩石可侵蚀性之间的量化关系可帮助从地形数据来评估气候控制条件以及将气候反馈融进景观演变模型中。


Chemical weathering as a mechanism for the climatic control of bedrock river incision


Feedbacks between climate, erosion and tectonics influence the rates of chemical weathering reactions which can consume atmospheric CO2 and modulate global climate. However, quantitative predictions for the coupling of these feedbacks are limited because the specific mechanisms by which climate controls erosion are poorly understood. Here we show that climate-dependent chemical weathering controls the erodibility of bedrock-floored rivers across a rainfall gradient on the Big Island of Hawai‘i. Field data demonstrate that the physical strength of bedrock in streambeds varies with the degree of chemical weathering, which increases systematically with local rainfall rate. We find that incorporating the quantified relationships between local rainfall and erodibility into a commonly used river incision model is necessary to predict the rates and patterns of downcutting of these rivers. In contrast to using only precipitation-dependent river discharge to explain the climatic control of bedrock river incision, the mechanism of chemical weathering can explain strong coupling between local climate and river incision.

来源: Nature 浏览次数:0


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