Quantifying Climatic Control of Erosional Efficiency

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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.