Loughborough University
Browse
2012_Describe_exp.pdf (601.52 kB)

Subglacial bedforms reveal an exponential size-frequency distribution

Download (601.52 kB)
journal contribution
posted on 2013-08-30, 08:52 authored by John HillierJohn Hillier, Mike J. Smith, C.D. Clark, C.R. Stokes, M. Spagnolo
Subglacial bedforms preserved in deglaciated landscapes record characteristics of past ice-sediment flow regimes, providing insight into subglacial processes and ice sheet dynamics. Individual forms vary considerably, but they can often be grouped into coherent fields, typically called flow-sets, that reflect discrete episodes of ice flow. Within these, bedform size-frequency distributions (predominantly height, width and length) are currently described by several statistics (e.g., mean, median, and standard deviation) that, arguably, do not best capture the defining characteristics of these populations. This paper seeks to create a better description based upon semi-log plots, which reveal that the frequency distributions of bedform dimensions (drumlin, mega-scale glacial lineation, and ribbed moraine) plot as straight lines above the mode (φ). This indicates, by definition, an exponential distribution, for which a simple and easily calculated, yet statistically rigorous, description is designed. Three descriptive parameters are proposed: gradient (λ; the exponent, characterising bedforms likely least affected by non-glacial factors), area-normalised y-intercept (β; quantifying spatial density), and the mode (φ). Below φ, small features are less prevalent due to i) measurement: data, sampling and mapping fidelity; ii) possible post-glacial degradation; or iii) genesis: not being created sub-glacially. This new description has the benefit of being insensitive to the impact of potentially unmapped or degraded smaller features and better captures properties relating to ice flow. Importantly, using λ, flow sets can now be more usefully compared with each other across all deglaciated regions and with the output of numerical ice sheet models. Applications may also exist for analogous fluvial and aeolian bedforms. Identifying the characteristic exponential and that it is typical of 'emergent' subglacial bedforms is a new and potentially powerful constraint on their genesis, perhaps indicating that ice-sediment interaction is fundamentally stochastic in nature. © 2013 Elsevier B.V.

History

School

  • Social Sciences

Department

  • Geography and Environment

Citation

HILLIER, J.K. ... et al., 2013. Subglacial bedforms reveal an exponential size-frequency distribution. Geomorphology, 190 pp. 82 - 91.

Publisher

© Elsevier B.V.

Version

  • AM (Accepted Manuscript)

Publication date

2013

Notes

This article was published in the journal, Geomorphology [© Elsevier B.V.] and the definitive version is available at: http://dx.doi.org/10.1016/j.geomorph.2013.02.017

ISSN

0169-555X

Language

  • en

Usage metrics

    Loughborough Publications

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC