Erosion beneath Pleistocene Glaciers and Ice Sheets

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This award will support development of a new method to measure erosion rates beneath glaciers and ice sheets. The method is based on interpretation of depth profiles of cosmic-ray-produced nuclides (Be-10, Al-26 and Cl-36) beneath glaciated bedrock surfaces. Nuclide concentrations, ratios, and profile gradients are sensitive to the exposure and erosion history. We will invert these data to determine erosion over the past 0.5-1 million years. To verify the method we will measure profiles at up- and downflow ends of glacial landforms in eastern Maine, where existing theory predicts different erosion processes and strongly contrasting erosion rates. This work will provide a quantitative method for the study of landscape evolution in glaciated terrain. This will allow geomorphologists to re-examine long-standing questions concerning the erosional effects of the Pleistocene ice sheets, formation rates of characteristic glacial landforms, and the origin of glacial valley profiles. Broader impacts of the work will include: (i) Graduate student training, (ii) Undergraduate participation in field- and laboratory-based research, (iii) Collaboration with the Maine Granite Industry Museum, where project results will be used to explain the glacial imprint on the surrounding landscape, and (iv) Evaluation of glacial erosion as a risk factor in planning for long-term isolation of nuclear waste in high-latitude countries.