Climatic control of bedrock river incision
Climatic control of bedrock river incision
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DOI：
10.1038/nature11982
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发表时间：
2013-04-11
期刊：
影响因子：
64.8
通讯作者：
Perron, J. Taylor
中科院分区：
文献类型：
--
作者：
Ferrier, Ken L.;Huppert, Kimberly L.;Perron, J. Taylor
基岩河流切割推动了地球表面大部分地形的发展(1-3)，从而塑造了山脉带的结构(4)，并通过其对土壤侵蚀、营养通量(6)和全球气候(7)的影响调节了地球的宜居性。虽然长期以来一直认为河流切割率应强烈取决于降雨率，但事实证明，量化降雨率对基岩河流切割率的影响是困难的，部分原因是河流切割率难以测量，部分原因是非气候因素可能掩盖已测量河流切割率的地点的气候影响(8，9)。在这里，我们给出了跨越地球上最陡峭的降雨梯度之一的河流切割率的测量结果，这表明降雨率确实影响到基岩河流切割率的长期。我们对夏威夷考阿岛上的一系列河流应用了一个广泛使用的基岩河流切割经验定律(3，9-11)，这些河流的年平均降雨量从0.5米到9.5米(参考文献)。(12)--全球范围的70%以上(13)--数百万年来平均的河流切割率可以从河流峡谷的深度和火山基岩的年龄推断出来。时间平均分析和瞬变河道切割的数值模拟都表明，基岩河道切割穿越考阿岛的长期效率与上游平均年降雨量呈正相关。我们通过证明我们的测量结果与河流切割速率与水流功率(河床上水流的能量消耗速率)的线性关系一致，为这一结果提供了理论背景。这些观察结果为气候和河流切割之间长期提出的耦合提供了罕见的经验证据，表明以前提出的地形、气候和构造之间的反馈可能会发生。
Bedrock river incision drives the development of much of Earth's surface topography(1-3), and thereby shapes the structure of mountain belts(4) and modulates Earth's habitability through its effects on soil erosion(5), nutrient fluxes(6) and global climate(7). Although it has long been expected that river incision rates should depend strongly on precipitation rates, quantifying the effects of precipitation rates on bedrock river incision rates has proved difficult, partly because river incision rates are difficult to measure and partly because non-climatic factors can obscure climatic effects at sites where river incision rates have been measured(8,9). Here we present measurements of river incision rates across one of Earth's steepest rainfall gradients, which show that precipitation rates do indeed influence long-term bedrock river incision rates. We apply a widely used empirical law for bedrock river incision(3,9-11) to a series of rivers on the Hawaiian island of Kaua'i, where mean annual precipitation ranges from 0.5 metres to 9.5 metres (ref. 12)-over 70 per cent of the global range(13)-and river incision rates averaged over millions of years can be inferred from the depth of river canyons and the age of the volcanic bedrock. Both a time-averaged analysis and numerical modelling of transient river incision reveal that the long-term efficiency of bedrock river incision across Kaua'i is positively correlated with upstream-averaged mean annual precipitation rates. We provide theoretical context for this result by demonstrating that our measurements are consistent with a linear dependence of river incision rates on stream power, the rate of energy expenditure by the flow on the riverbed. These observations provide rare empirical evidence for the long-proposed coupling between climate and river incision, suggesting that previously proposed feed-backs among topography, climate and tectonics may occur.