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Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology

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Title: Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology
Authors: Cooper, M
Jordan, T
Schroeder, D
Siegert, M
Williams, C
Bamber, J
Item Type: Journal Article
Abstract: The subglacial environment of the Greenland Ice Sheet (GrIS) is poorly constrained both in its bulk properties, for example geology, the presence of sediment, and the presence of water, and interfacial conditions, such as roughness and bed rheology. There is, therefore, limited understanding of how spatially heterogeneous subglacial properties relate to ice-sheet motion. Here, via analysis of 2 decades of radio-echo sounding data, we present a new systematic analysis of subglacial roughness beneath the GrIS. We use two independent methods to quantify subglacial roughness: first, the variability in along-track topography – enabling an assessment of roughness anisotropy from pairs of orthogonal transects aligned perpendicular and parallel to ice flow and, second, from bed-echo scattering – enabling assessment of fine-scale bed characteristics. We establish the spatial distribution of subglacial roughness and quantify its relationship with ice flow speed and direction. Overall, the beds of fast-flowing regions are observed to be rougher than the slow-flowing interior. Topographic roughness exhibits an exponential scaling relationship with ice surface velocity parallel, but not perpendicular, to flow direction in fast-flowing regions, and the degree of anisotropy is correlated with ice surface speed. In many slow-flowing regions both roughness methods indicate spatially coherent regions of smooth beds, which, through combination with analyses of underlying geology, we conclude is likely due to the presence of a hard flat bed. Consequently, the study provides scope for a spatially variable hard- or soft-bed boundary constraint for ice-sheet models.
Issue Date: 26-Nov-2019
Date of Acceptance: 29-Oct-2019
URI: http://hdl.handle.net/10044/1/75216
DOI: 10.5194/tc-13-3093-2019
ISSN: 1994-0416
Publisher: Copernicus Publications
Start Page: 3093
End Page: 3115
Journal / Book Title: The Cryosphere
Volume: 13
Copyright Statement: ©2019. The Authors. This is an open access article under theterms of the Creative CommonsAttribution License, which permits use,distribution and reproduction in anymedium, provided the original work isproperly cited. (https://creativecommons.org/licenses/by/4.0/)
Sponsor/Funder: Natural Environment Research Council (NERC)
Funder's Grant Number: GEOG.RE2356
Keywords: 0405 Oceanography
0406 Physical Geography and Environmental Geoscience
Meteorology & Atmospheric Sciences
Publication Status: Published
Appears in Collections:Earth Science and Engineering
Centre for Environmental Policy
Faculty of Natural Sciences



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