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High resolution measurements of ice motion along a similar to 120 km transect in a land-terminating section of the GrIS reveal short-term velocity variations (<1 day), which are forced by rapid variations in meltwater input to the subglacial drainage system from the ice sheet surface. The seasonal changes in ice velocity at low elevations (<1000 m) are dominated by events lasting from 1 day to 1 week, although daily cycles are largely absent at higher elevations, reflecting different patterns of meltwater input. Using a simple model of subglacial conduit behavior we show that the seasonal record of ice velocity can be understood in terms of a time-varying water input to a channelized subglacial drainage system. Our investigation substantiates arguments that variability in the duration and rate, rather than absolute volume, of meltwater delivery to the subglacial drainage system are important controls on seasonal patterns of subglacial water pressure, and therefore ice velocity. We suggest that interpretations of hydro-dynamic behavior in land-terminating sections of the GrIS margin which rely on steady state drainage theories are unsuitable for making predictions about the effect of increased summer ablation on future rates of ice motion.
Author(s): Bartholomew I, Nienow P, Sole A, Mair D, Cowton T, King MA
Publication type: Article
Publication status: Published
Journal: Journal of Geophysical Research: Earth Surface
Year: 2012
Volume: 117
Issue: F3
Print publication date: 07/07/2012
ISSN (print): 0148-0227
ISSN (electronic): 2156-2202
Publisher: American Geophysical Union
URL: http://dx.doi.org/10.1029/2011JF002220
DOI: 10.1029/2011JF002220
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