IngentaConnect Observations of englacial water passages: a fracture-dominated sy...

Authors: Fountain, Andrew G.; Schlichting, Robert B.; Jansson, Peter; Jacobel, Robert W.

Source: Annals of Glaciology, Volume 40, Number 1, January 2005 , pp. 25-30(6)

Publisher: International Glaciological Society

Abstract:

To test models of the hydraulics and geometry of englacial conduits, 48 holes (3900 m of ice) were drilled into Storglaciaren, Sweden, in search of conduits. About 79% of the holes intersected a hydraulically connected englacial feature. A video camera was used to examine the features and measure local water-flow rates. Because of the extremely clear ice that surrounded most features, their geometry could not be discerned. Of the remaining features, 80% (36) were fracture-like, 16% (6) were of complex geometry, and 4% (2) exhibited a conduit-like geometry. The fracture-like features exhibited steep plunges (∼70°), narrow openings (∼40 mm) and slow water-flow speeds (∼10 mm s⁻¹). We argue that these fracture-like features are indeed englacial fractures of unknown origin. The depth to fractures intersection varied from near the glacier surface to 96% of local ice depth, with a maximum depth of 131 m. Few hydraulically connected fractures exhibited water motion, indicating some preferential flow pathways exist. We found one 'traditional' englacial conduit after an intentional search in a field of moulins. These results suggest that englacial water flow is conveyed through a ubiquitous network of fractures and that conduits are relatively rare.

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Observations of englacial water passages: a fracture-dominated system