Journal
JOURNAL OF GLACIOLOGY
Volume 58, Issue 211, Pages 926-940Publisher
CAMBRIDGE UNIV PRESS
DOI: 10.3189/2012JoG11J189
Keywords
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Funding
- US National Science Foundation
- Nordic Research Opportunity
- EAR Postdoctoral Fellowship [0946767]
- American Philosophical Society Lewis and Clarke Fund for Exploration and Field Research
- Evolving Earth Foundation
- University of Florida
- University Centre in Svalbard
- ice2sea project of the European Union 7th Framework Programme [226375]
- Division Of Earth Sciences
- Directorate For Geosciences [0946767] Funding Source: National Science Foundation
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Subglacial conduit systems are thought to consist of dendritic networks that exist at lower pressure than distributed systems and have locations that are determined by theoretical hydraulic potential. On glaciers with moulins, however, meltwater is delivered to glacier beds at discrete points, violating assumptions of uniform recharge needed to calculate potential. To understand how moulins affect subglacial conduit hydrology, we used speleological techniques to map 0.4 km of subglacial conduit at the base of a moulin in Hansbreen, Svalbard, and compared our observations with theoretical predictions. The conduit began in an area predicted to lack drainage, crossed equipotential contours at oblique rather than right angles and was locally anastomotic rather than dendritic. We propose moulin locations, which are determined by the locations of supraglacial streams and crevasses, control locations of subglacial recharge. Because conduits have no direct causal relationship with gradients in effective pressure, this recharge can form conduits in areas of glacier beds that may not be predicted by hydraulic potential theory to have conduits. Recharge by moulins allows hydraulic head to increase in conduits faster and to higher values than in adjacent distributed systems, resulting in an increase rather than a decrease in glacier sliding speeds above subglacial conduits.
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