Basal Drainage System Response to Increasing Surface Melt on the Greenland Ice Sheet
Draining Through Ice
Water formed by surface melting of the Greenland Ice Sheet is transferred rapidly to the underlying bedrock, but how the water is then dispersed is less clear. This question is important because how the ice-rock interface is lubricated affects how fast the ice sheet moves. Existing conceptual models are based on observations of mountain glaciers, but Meierbachtol et al. (p. 777; see the Perspective by Lüthi) now show that those ideas may not be applicable to the Greenland Ice Sheet. Measuring water pressures in a transect of 23 boreholes revealed that drainage structures differ between the edge, where large melt channels form, and further inland, where more distributed pathways are found.
Abstract
Surface meltwater reaching the bed of the Greenland ice sheet imparts a fundamental control on basal motion. Sliding speed depends on ice/bed coupling, dictated by the configuration and pressure of the hydrologic drainage system. In situ observations in a four-site transect containing 23 boreholes drilled to Greenland’s bed reveal basal water pressures unfavorable to water-draining conduit development extending inland beneath deep ice. This finding is supported by numerical analysis based on realistic ice sheet geometry. Slow meltback of ice walls limits conduit growth, inhibiting their capacity to transport increased discharge. Key aspects of current conceptual models for Greenland basal hydrology, derived primarily from the study of mountain glaciers, appear to be limited to a portion of the ablation zone near the ice sheet margin.
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Supplementary Material
Summary
Materials and Methods
Supplementary Text
Figs. S1 to S6
Tables S1 to S3
Resources
File (meierbachtol.sm.pdf)
References and Notes
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Science
Volume 341 | Issue 6147
16 August 2013
16 August 2013
Copyright
Copyright © 2013, American Association for the Advancement of Science.
Submission history
Received: 31 January 2013
Accepted: 2 July 2013
Published in print: 16 August 2013
Acknowledgments
We thank J. Johnson for his thoughtful review and comments that improved this manuscript. Many thanks to all those who provided field assistance. This work is funded by SKB-Posiva-NWMO through the Greenland Analogue Project and NSF (Office of Polar Programs–Arctic Natural Sciences grant no. 0909495).
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