Inferring subglacial drainage evolution beneath the Greenland Ice Sheet using artificial tracer techniques
Abstract
Models of Greenland Ice Sheet evolution require an improved representation of the link between subglacial hydrology and ice dynamics. Over the past three melt seasons (2009-2011), artificial tracer experiments, using both fluorescent dye and sulphur hexafluoride (SF6), have been conducted via injections to moulins up to 40 km from the ice sheet margin. These data have been used to gain an improved insight into the patterns and development of subglacial drainage beneath the Greenland Ice Sheet. Whilst dye tracing is a well established method in glaciology, SF6 tracing is relatively new and presents major challenges, in particular with respect to the low solubility of SF6 in water. However, SF6 has some significant advantages, most significantly its low detection limit (order 10-15 mol/L) that allows for much greater dispersion and consequently longer traces than is practical with dye. Here, we present a summary of results obtained from the three melt seasons. Most notably we found that (1) repeat traces from the same moulin reveal an increasingly efficient (channelised) drainage system as the melt season progresses, with the most rapid evolution observed shortly after the onset of surface melt; (2) traces injected to different moulins show an increasingly inefficient (distributed) drainage system with increasing distance from the ice sheet margin; and (3) our observations share many similarities with dye tracing studies conducted at much smaller glaciers, such as those in the Alps. Our results will be used to optimise a numerical model of subglacial channel evolution for the Greenland Ice Sheet that is currently under development.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.C13C..06W
- Keywords:
-
- 0726 CRYOSPHERE / Ice sheets;
- 0774 CRYOSPHERE / Dynamics;
- 0776 CRYOSPHERE / Glaciology;
- 0794 CRYOSPHERE / Instruments and techniques