期刊
JOURNAL OF GLACIOLOGY
卷 62, 期 234, 页码 696-713出版社
CAMBRIDGE UNIV PRESS
DOI: 10.1017/jog.2016.63
关键词
ice sheet; ice stream; sticky spots; subglacial bedforms
资金
- Natural Environment Research Council grant [NE/J00782X/1]
- Natural Environment Research Council [NE/J00782X/1] Funding Source: researchfish
- NERC [NE/J00782X/1] Funding Source: UKRI
- Office of Polar Programs (OPP)
- Directorate For Geosciences [1043481] Funding Source: National Science Foundation
Rapidly-flowing ice streams are an important mechanism through which ice sheets lose mass, and much work has been focussed on elucidating the processes that increase or decrease their velocity. Recent work using standard inverse methods has inferred previously-unrecognised regular patterns of high basal shear stress ('sticky spots' > 200 kPa) beneath a number of ice streams in Antarctica and Greenland, termed 'traction ribs'. They appear at a scale intermediate between smaller ribbed moraines and much larger mega-ribs observed on palaeo-ice sheet beds, but it is unclear whether they have a topographic expression at the bed. Here, we report observations of riblike bedforms from DEMs along palaeo-ice stream beds in western Canada that resemble both the pattern and dimensions of traction ribs. Their identification suggests that traction ribs may have a topographic expression that lies between, and partly overlaps with, ribbed moraines and much larger mega-ribs. These intermediate-sized bedforms support the notion of a ribbed bedform continuum. Their formation remains conjectural, but our observations from palaeo-ice streams, coupled with those from modern ice masses, suggest they are related to wave-like instabilities occurring in the coupled flow of ice and till and modulated by subglacial meltwater drainage. Their form and pattern may also involve glaciotectonism of subglacial sediments.
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