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The periodic topography of ice stream beds : insights from the Fourier spectra of mega-scale glacial lineations.

Spagnolo, Matteo and Bartholomaus, Timothy C. and Clark, Chris D. and Stokes, Chris R. and Atkinson, Nigel and Dowdeswell, Julian A. and Ely, Jeremy C. and Graham, Alastair G. C. and Hogan, Kelly A. and King, Edward C. and Larter, Robert D. and Livingstone, Stephen J. and Pritchard, Hamish D. (2017) 'The periodic topography of ice stream beds : insights from the Fourier spectra of mega-scale glacial lineations.', Journal of geophysical research : earth surface., 122 (7). pp. 1355-1373.

Abstract

Ice stream bed topography contains key evidence for the ways ice streams interact with, and are potentially controlled by, their beds. Here we present the first application of two-dimensional Fourier analysis to 22 marine and terrestrial topographies from 5 regions in Antarctica and Canada, with and without mega-scale glacial lineations (MSGLs). We find that the topography of MSGL-rich ice stream sedimentary beds is characterized by multiple, periodic wavelengths between 300 and 1200 m and amplitudes from decimeters to a few meters. This periodic topography is consistent with the idea that instability is a key element to the formation of MSGL bedforms. Dominant wavelengths vary among locations and, on one paleo ice stream bed, increase along the direction of ice flow by 1.7 ± 0.52% km−1. We suggest that these changes are likely to reflect pattern evolution via downstream wavelength coarsening, even under potentially steady ice stream geometry and flow conditions. The amplitude of MSGLs is smaller than that of other fluvial and glacial topographies but within the same order of magnitude. However, MSGLs are a striking component of ice stream beds because the topographic amplitude of features not aligned with ice flow is reduced by an order of magnitude relative to those oriented with the flow direction. This study represents the first attempt to automatically derive the spectral signatures of MSGLs. It highlights the plausibility of identifying these landform assemblages using automated techniques and provides a benchmark for numerical models of ice stream flow and subglacial landscape evolution.

Item Type:Article
Full text:(VoR) Version of Record
Available under License - Creative Commons Attribution.
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Full text:(VoR) Version of Record
Available under License - Creative Commons Attribution.
Download PDF
(7144Kb)
Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1002/2016JF004154
Publisher statement:© 2017. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Date accepted:17 June 2017
Date deposited:25 July 2017
Date of first online publication:15 July 2017
Date first made open access:No date available

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