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。关于气候对千年或更长时间尺度的侵蚀速度的控制，人们对此知之甚少。尽管细节不同，但景观演变模型都预测河流流量和侵蚀率之间存在正向、单调的关系。然而，由于很难在大规模自然系统中分离变量，在景观尺度上支持这一基本预期的数据很少。事实上，现有的一些最令人信服的数据显示了侵蚀率和地形之间的强烈关系，但年平均降雨量和侵蚀率之间几乎没有显著的相关性。本研究将检验年平均降雨量强烈影响侵蚀效率的假设，即地势与侵蚀率之间的函数关系将从同一岩石类型下的干旱集水区系统地变化为日益潮湿的集水区。千年尺度的侵蚀速率将通过对分布在不同气候环境但相似基岩起伏范围的六个野外地点的一套集水区的宇宙放射性核素测量来确定。通过对不同地点的比较，这些数据将量化年平均降雨量和侵蚀速率之间的关系。与气候和侵蚀之间的关系相比，有几个问题对塑造地球表面更重要。因此，这里所追求的研究问题对直接与社会相关的问题具有直接影响，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于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的风化速率非常感兴趣，因为这个过程会提取大气中的二氧化碳，从而减少温室气体的水平。侵蚀将影响硅酸盐风化的速度，因此，将直接影响二氧化碳的去除。在控制盆地泥沙涌入方面，气候和构造隆升的区分一直是地质科学界的一个长期问题。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.