Few problems are more fundamental to the study of geomorphology than the relationship between climate and erosion. The role of climate as a driver for erosion and sediment transport is important to surface processes that act over timescales of individual storms to millions of years. Not surprisingly, climates role in surface processes is equally central to fundamental problems in allied fields like geochemistry and tectonics/geodynamics. For instance, in geochemistry there is a great deal of interest in how climate controls silicate weathering rates, a key feedback in the carbon cycle. Recent data shows chemical weathering rates can be strongly modulated by physical erosion rates. As such, the question of how strongly climate controls physical erosion rates becomes directly relevant. In the fields of tectonics and geodynamics, there is vigorous inquiry into the potential for dynamic two-way interactions between climate and tectonics. The expected link between climate and erosion rate is the cornerstone of this extensive literature. Given the far-reaching importance of how climate affects erosion rate, it is surprising to realize how little we know about it quantitatively. Though details vary, models for the long-term relationships among climate and erosion rate at the catchment scale all predict a positive, monotonic relationship between river discharge and channel incision rate. However, little data exists to support this fundamental expectation at the landscape-scale due to the relative difficulty in isolating variables over large-scale complex systems. Indeed, some of the most convincing data available shows strong relationships between erosion rate and relief (or other topographic metrics), but little or no significant correlation between mean annual rainfall and erosion rate. We propose to test the hypothesis that mean annual precipitation (MAP) does in fact strongly influence the efficiency of erosion. That is, we expect that the relationship between relief and erosion rate will change systematically from arid to semi-arid to increasingly humid catchments underlain by the same lithology i.e. more efficient wet environments will yield higher erosion rates for the same topography than less efficient dry environments. Our approach will be to use well established detrital cosmogenic radionuclide (10Be) methods to measure millennial-scale erosion rates in a suite of catchments in 6 field sites in different climatic settings but with similar ranges of relief cut in similar granitoid lithologies. These data will allow us to build relations between topographic metrics and erosion rates in field sites with MAP ranging from ~0.2 to ~3.0 m/yr. From these data, we will definitively know how strong the relationship between MAP and erosional efficiency is.
|Effective start/end date||8/15/09 → 9/30/13|
- National Science Foundation (NSF): $365,897.00
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