Greenland ice sheet motion insensitive to exceptional meltwater forcing

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Tedstone, A. J., Nienow, P. W., Sole, A. J., Mair, D. W. F., Cowton, Tom, Bartholomew, I. D., King, M. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2013
• Subjects: Greenland; glacier; Ice Sheet
• Online Access: https://research-portal.st-andrews.ac.uk/en/researchoutput/greenland-ice-sheet-motion-insensitive-to-exceptional-meltwater-forcing(38328ecb-ff72-4817-a581-cbe46ba9b107).html; https://doi.org/10.1073/pnas.1315843110

Changes to the dynamics of the Greenland ice sheet can be forced by various mechanisms including surface-melt-induced ice acceleration and oceanic forcing of marine-terminating glaciers. We use observations of ice motion to examine the surface melt-induced dynamic response of a land-terminating outlet glacier in south-west Greenland to the exceptional melting observed in 2012. During summer, meltwater generated on the Greenland Ice Sheet (GrIS) surface accesses the ice sheet bed, lubricating basal motion and resulting in periods of faster ice flow. However, the net impact of varying meltwater volumes upon seasonal and annual ice flow, and thus sea level rise, remains unclear. We show that two extreme melt events (98.6% of the GrIS surface experienced melting on 12 July -the most significant melt event since 1889 - and 79.2% on 29 July) and summer ice sheet runoff 3.9? above the 1958-2011 mean resulted in enhanced summer ice motion relative to the average melt year of 2009. However, despite record summer melting, subsequent reduced winter ice motion resulted in 6% less net annual ice motion in 2012 than in 2009. Our findings suggest that surface melt-induced acceleration of land-terminating regions of the ice sheet will remain insignificant even under extreme melting scenarios.