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Stabilizing feedbacks in glacier-bed erosion

Abstract

Glaciers often erode, transport and deposit sediment much more rapidly than nonglacial environments1, with implications for the evolution of glaciated mountain belts and their associated sedimentary basins. But modelling such glacial processes is difficult, partly because stabilizing feedbacks similar to those operating in rivers2,3 have not been identified for glacial landscapes. Here we combine new and existing data of glacier morphology and the processes governing glacier evolution from diverse settings to reveal such stabilizing feedbacks. We find that the long profiles of beds of highly erosive glaciers tend towards steady-state angles opposed to and slightly more than 50 per cent steeper than the overlying ice–air surface slopes, and that additional subglacial deepening must be enabled by non-glacial processes. Climatic or glaciological perturbations of the ice–air surface slope can have large transient effects on glaciofluvial sediment flux and apparent glacial erosion rate.

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Figure 1: Cartoons of sediment-transport capacity and sediment load in subglacial streams, for a glacier lacking supercooling (a), and for a glacier far into the supercooling field (b).

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Acknowledgements

We thank K. Cuffey for advice and for comments on this manuscript, including help with the third paragraph. We thank our many colleagues in studying the Matanuska glacier system, including S. Arcone, S. Kopczynski, R. Bigl, J. Denner, S. Ensminger, T. Johnston and J. Strasser, and we thank R. Hooke for suggestions. Discussions with B. Hallet, G. Clarke, T. Creyts, S. Tulaczyk and other colleagues helped clarify our ideas. We thank NSF and CRREL for funding.Author contributions R.B.A. led collaborative theory development and writing, D.E.L., G.J.L. and E.B.E. provided extensive data and insights on glacier processes, and G.S.B. produced new geophysical data at Matanuska glacier.

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Correspondence to R. B. Alley.

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Alley, R., Lawson, D., Larson, G. et al. Stabilizing feedbacks in glacier-bed erosion. Nature 424, 758–760 (2003). https://doi.org/10.1038/nature01839

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