Evolution of the subglacial drainage system beneath the Greenland Ice Sheet revealed by tracers

• Published in: Nature geoscience Vol. 6; no. 3; pp. 195 - 198
• Main Authors: Chandler, D. M., Wadham, J. L., Lis, G. P., Cowton, T., Sole, A., Bartholomew, I., Telling, J., Nienow, P., Bagshaw, E. B., Mair, D., Vinen, S., Hubbard, A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2013; Nature Publishing Group
• Subjects: 704/106/125; 704/106/242; 704/2151/215; Climate change; Drainage systems; Earth Sciences; Earth System Sciences; Flow characteristics; Geochemistry; Geology; Geophysics/Geodesy; Ice; letter; Meltwater; Tracers; Water flow; PN, Greenland, Greenland Ice Sheet
• ISSN: 1752-0894; 1752-0908
• DOI: 10.1038/ngeo1737

The fast flow of glaciers in Greenland during the summer season has been attributed to seasonal increases in subglacial melt water. Tracking the flow of subglacial water using geochemical tracers reveals the establishment of an increasingly efficient drainage network as the melt season progresses. Predictions of the Greenland Ice Sheet’s response to climate change are limited in part by uncertainty in the coupling between meltwater lubrication of the ice-sheet bed and ice flow 1 , 2 , 3 . This uncertainty arises largely from a lack of direct measurements of water flow characteristics at the bed of the ice sheet. Previous work has been restricted to indirect observations based on seasonal and spatial variations in surface ice velocities 4 , 5 , 6 , 7 and on meltwater flux 8 . Here, we employ rhodamine and sulphur hexafluoride tracers, injected into the drainage system over three melt seasons, to observe subglacial drainage properties and evolution beneath the Greenland Ice Sheet, up to 57 km from the margin. Tracer results indicate evolution from a slow, inefficient drainage system to a fast, efficient channelized drainage system over the course of the melt season. Further inland, evolution to efficient drainage occurs later and more slowly. An efficient routing of water was established up to 41 km or more from the margin, where the ice is approximately 1 km thick. Overall, our findings support previous interpretations of drainage system characteristics, thereby validating the use of surface observations as a means of investigating basal processes.