Quantifying Climatic Control of Erosional Efficiency

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。在千年或更长时间尺度上，气候对侵蚀速率的控制在数量上知之甚少。尽管细节各不相同，但景观演化模型都预测河流流量与侵蚀速率之间存在正单调关系。然而，由于在大尺度自然系统中难以隔离变量，因此在景观尺度上支持这一基本期望的数据很少。事实上，现有的一些最令人信服的数据表明，侵蚀速率与地形起伏之间存在很强的关系，但年平均降水量与侵蚀速率之间几乎没有显著的相关性。这项研究将检验平均年降水量强烈影响侵蚀效率的假设，从而使地形和侵蚀速率之间的函数关系从干旱到同一岩石类型下日益潮湿的集水区将系统地发生变化。千年尺度的侵蚀速率将通过宇宙形成的放射性核素测量来确定，这些测量是对分布在不同气候环境下的六个野外地点的一套集水区进行的，但在相似的基岩上具有相似的起伏范围。通过跨站点的比较，这些数据将量化年平均降水量和侵蚀率之间的关系。在塑造地球表面的过程中，没有什么问题比气候和侵蚀之间的关系更重要了。因此，这里所追求的研究问题对直接的社会相关问题有直接的影响，包括气候对水库沉积速率、自然灾害和土壤侵蚀速率的影响。气候在地表过程中的作用对相关领域的基本问题同样重要。例如，人们对气候如何控制硅酸盐风化速率非常感兴趣，因为这一过程可以提取大气中的二氧化碳，从而降低温室气体的水平。侵蚀将影响硅酸盐风化的速率，因此，将直接影响二氧化碳的去除。在控制盆地泥沙流入方面，气候与构造隆升难以区分是地质科学中一个长期存在的问题。这项研究将为深入了解这一过程提供新的工具。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Little is known quantitatively about the climatic control on erosion rates at millennial or longer timescales. Although details vary, landscape evolution models all predict a positive, monotonic relationship between river discharge and erosion rate. However, little data exists to support this fundamental expectation at the landscape scale due to the difficulty in isolating variables in large-scale natural systems. Indeed, some of the most convincing data available shows strong relationships between erosion rate and relief, but little or no significant correlation between mean annual precipitation and erosion rate. This research will test the hypothesis that mean annual precipitation strongly influences the efficiency of erosion, such that the functional relationship between relief and erosion rate will change systematically from arid to increasingly humid catchments underlain by the same rock type. Millennial-scale erosion rates will be determined via cosmogenic radionuclide measurements for a suite of catchments in six field sites distributed in different climatic settings, but with similar ranges of relief in similar bedrock. By comparing across sites, these data will quantify the relationship between mean annual precipitation and erosion rate.Few problems are more fundamental to shaping the Earth's surface than the relationship between climate and erosion. Consequently, the research questions pursued here have direct implications for problems of immediate societal relevance including climatic impacts on reservoir sedimentation rates, natural hazards, and rates of soil erosion. The role of climate in surface processes is equally central to fundamental problems in allied fields. For example, there is a great deal of interest in how climate controls silicate weathering rates, since this process extracts atmospheric carbon dioxide and thus acts to reduce the level of greenhouse gases. Erosion will affect the rate of silicate weathering, and, as such, will directly influence this removal of carbon dioxide. The difficulty of distinguishing climate from tectonic uplift in controlling sediment influx into basins has been a long-standing problem in the geological sciences. This research will provide new tools for gaining insight into this process.