Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78712, USA.
Department of Earth and Environmental Sciences, Tulane University, New Orleans, Louisiana 70118, USA.
Nature. 2016 Apr 14;532(7598):223-7. doi: 10.1038/nature17449.
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.
气候、侵蚀和构造之间的反馈影响着化学风化反应的速率，这些反应可以消耗大气中的二氧化碳并调节全球气候。然而，由于气候控制侵蚀的具体机制尚不清楚，因此对这些反馈的耦合进行定量预测受到限制。在这里，我们表明，气候相关的化学风化控制了夏威夷大岛降雨梯度上基岩河床河流的侵蚀率。实地数据表明，河床中基岩的物理强度随化学风化程度而变化，而化学风化程度则随当地降雨量的增加而系统增加。我们发现，将局部降雨和侵蚀率之间的量化关系纳入常用的河流侵蚀模型中，对于预测这些河流的下切速率和模式是必要的。与仅使用降水依赖的河流流量来解释基岩河流侵蚀的气候控制相比，化学风化的机制可以解释局部气候与河流侵蚀之间的强耦合。
