Understanding the flow of water through the body of a glacier is important, because the spatial distribution of water and the rate of infiltration to the glacier bottom is one control on water storage and pressure, glacier sliding and surging, and the release of glacial outburst floods1,2,3. According to the prevailing hypothesis, this water flow takes place in a network of tubular conduits4,5. Here we analyse video images from 48 boreholes drilled into the small Swedish glacier Storglaciären, showing that the glacier's hydrological system is instead dominated by fractures that convey water at slow speeds. We detected hydraulically connected fractures at all depths, including near the glacier bottom. Our observations indicate that fractures provide the main pathways for surface water to reach deep within the glacier, whereas tubular conduits probably form only in special circumstances. A network of hydraulically linked fractures offers a simple explanation for the origin and evolution of the englacial water flow system and its seasonal regeneration. Such a fracture network also explains radar observations that reveal a complex pattern of echoes rather than a system of conduits. Our findings may be important in understanding the catastrophic collapse of ice shelves and rapid hydraulic connection between the surface and bed of an ice sheet.
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We thank S. Frödin-Nyman, M. Nyman, R. Pettersson, and R. Hock. J. Walder and R. LeB. Hooke provided suggestions during the preparation of this manuscript. This work was supported by the Arctic Natural Sciences Section within the Office of Polar Programs of the US National Science Foundation. P.J.'s participation was funded by the Swedish Research Council. The Stockholm University, Tarfala Research Station provided excellent facilities and field assistance.
The authors declare that they have no competing financial interests.
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Fountain, A., Jacobel, R., Schlichting, R. et al. Fractures as the main pathways of water flow in temperate glaciers. Nature 433, 618–621 (2005). https://doi.org/10.1038/nature03296
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