Short-term variability in Greenland Ice Sheet motion forced by time-varying meltwater drainage: implications for the relationship between subglacial drainage system behavior and ice velocity

• Published in: Journal of Geophysical Research: Earth Surface
• Main Authors: Bartholomew, I, Nienow, P, Sole, A, Mair, D, Cowton, T, King, MA
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 2012
• Subjects: Earth Sciences; Geophysics; Geodesy; Greenland; Ice Sheet
• Online Access: https://doi.org/10.1029/2011JF002220; http://ecite.utas.edu.au/89655

High resolution measurements of ice motion along a ~120 km transect in aland-terminating section of the GrIS reveal short-term velocity variations (<1 day), whichare forced by rapid variations in meltwater input to the subglacial drainage system from theice sheet surface. The seasonal changes in ice velocity at low elevations (<1000 m) aredominated by events lasting from 1 day to 1 week, although daily cycles are largely absent athigher elevations, reflecting different patterns of meltwater input. Using a simple modelof subglacial conduit behavior we show that the seasonal record of ice velocity can beunderstood in terms of a time-varying water input to a channelized subglacial drainagesystem. Our investigation substantiates arguments that variability in the duration and rate,rather than absolute volume, of meltwater delivery to the subglacial drainage system areimportant controls on seasonal patterns of subglacial water pressure, and therefore icevelocity. We suggest that interpretations of hydro-dynamic behavior in land-terminatingsections of the GrIS margin which rely on steady state drainage theories are unsuitablefor making predictions about the effect of increased summer ablation on future rates ofice motion.