Geography
Document Type
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.
Publication Title
Cryosphere
Publication Date
2019
Volume
13
Issue
11
First Page
3093
Last Page
3115
ISSN
1994-0416
DOI
10.5194/tc-13-3093-2019
Keywords
flow velocity, ice flow, ice sheet, sound scattering, subglacial deposit, subglacial environment, surface roughness, topography
Repository Citation
Cooper, Michael A.; Jordan, Thomas M.; Schroeder, Dustin M.; Siegert, Martin J.; Williams, Christopher N.; and Bamber, Jonathan L., "Subglacial roughness of the Greenland Ice Sheet: Relationship with contemporary ice velocity and geology" (2019). Geography. 870.
https://commons.clarku.edu/faculty_geography/870
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Copyright
Published source must be acknowledged with citation:
Cooper, Michael A., et al. "Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology." The Cryosphere 13.11 (2019): 3093-3115.