Vertical extension of the subglacial drainage system into basal crevasses


Water plays a first-order role in basal sliding of glaciers and ice sheets and is often a key constituent of accelerated glacier motion1,2,3,4. Subglacial water is known to occupy systems of cavities and conduits at the interface between ice and the underlying bed surface, depending upon the history of water input and the characteristics of the substrate5. Full understanding of the extent and configuration of basal water is lacking, however, because direct observation is difficult. This limits our ability to simulate ice dynamics and the subsequent impacts on sea-level rise realistically. Here we show that the subglacial hydrological system can have a large volume of water occupying basal crevasses that extend upward from the bed into the overlying ice. Radar and seismic imaging combined with in situ borehole measurements collected on Bench Glacier, Alaska, reveal numerous water-filled basal crevasses with highly transmissive connections to the bed. Some crevasses extend many tens of metres above the bed and together they hold a volume of water equivalent to at least a decimetre layer covering the bed. Our results demonstrate that the basal hydrologic system can extend high into the overlying ice mass, where basal crevasses increase water-storage capacity and could potentially modulate basal water pressure. Because basal crevasses can form under commonly observed glaciological conditions, our findings have implications for interpreting and modelling subglacial hydrologic processes and related sliding accelerations of glaciers and ice sheets.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Map showing Bench Glacier, Alaska, and location of borehole and geophysical measurements.
Figure 2: Borehole drilling experiments.
Figure 3: 50-MHz 3D radar imaging of subsurface ice.


  1. 1

    Zwally, H. J. et al. Surface melt-induced acceleration of Greenland ice-sheet flow. Science 297, 218–222 (2002)

    CAS  Google Scholar 

  2. 2

    van de Wal, R. S. W. et al. Large and rapid melt-induced velocity changes in the ablation zone of the Greenland Ice Sheet. Science 321, 111–113 (2008)

    CAS  Google Scholar 

  3. 3

    Iken, A. & Bindschadler, R. A. Combined measurements of subglacial water pressure and surface velocity of Findelengletscher, Switzerland: conclusions about drainage system and sliding mechanism. J. Glaciol. 32, 101–119 (1986)

    Google Scholar 

  4. 4

    Jansson, P. Water-pressure and basal sliding on Storglaciaren, Northern Sweden. J. Glaciol. 41, 232–240 (1995)

    Google Scholar 

  5. 5

    Fountain, A. G. & Walder, J. S. Water flow through temperate glaciers. Rev. Geophys. 36, 299–328 (1998)

    Google Scholar 

  6. 6

    Hodge, S. M. Direct measurement of basal water pressures: a pilot study. J. Glaciol. 16, 205–218 (1976)

    Google Scholar 

  7. 7

    Iken, A. Measurement of water pressure in moulins as part of a movement study of the White Glacier, Axel Heiberg Island, Northwest Territories, Canada. J. Glaciol. 58, 53–58 (1974)

    Google Scholar 

  8. 8

    Lappegard, G., Kohler, J., Jackson, M. & Hagen, J. O. Characteristics of subglacial drainage systems deduced from load-cell measurements. J. Glaciol. 52, 137–148 (2006)

    Google Scholar 

  9. 9

    Walder, J. S. & Hallet, B. Geometry of former subglacial water channels and cavities. J. Glaciol. 23, 335–346 (1979)

    Google Scholar 

  10. 10

    van der Veen, C. J. Fracture mechanics approach to penetration of bottom crevasses on glaciers. Cold Reg. Sci. Technol. 27, 213–223 (1998)

    Google Scholar 

  11. 11

    Sugiyama, S. & Gudmundsson, G. H. Short-term variations in glacier flow controlled by subglacial water pressure at Lauteraargletscher, Bernese Alps, Switzerland. J. Glaciol. 50, 353–362 (2004)

    CAS  Google Scholar 

  12. 12

    Hooke, R. L. & Pohjola, V. A. Hydrology of a segment of a glacier situated in an overdeepening, Storglaciaren, Sweden. J. Glaciol. 40, 140–148 (1994)

    Google Scholar 

  13. 13

    Iken, A., Echelmeyer, K., Funk, M. & Harrison, W. Mechanisms of fast flow in Jakobshavn Isbræ, West Greenland. Part I: measurements of temperature and water level in deep boreholes. J. Glaciol. 39, 15–25 (1993)

    Google Scholar 

  14. 14

    Engelhardt, H., Humphrey, N., Kamb, B. & Fahnestock, M. Physical conditions at the base of a fast moving Antarctic ice stream. Science 248, 57–59 (1990)

    CAS  Google Scholar 

  15. 15

    Harper, J. T. et al. Spatial variability in the flow of a valley glacier: deformation of a large array of boreholes. J. Geophys. Res. 106, 8547–8562 (2001)

    Google Scholar 

  16. 16

    Anderson, R. et al. Strong feedbacks between hydrology and sliding of a small alpine glacier. J. Geophys. Res. 109, F000120 (2004)

    Google Scholar 

  17. 17

    Brown, J. M., Harper, J. T. & Bradford, J. H. A radar transparent layer in a temperate valley glacier: Bench Glacier, Alaska. Earth Surf. Process. Landf. 34, 1497–1506 (2009)

    Google Scholar 

  18. 18

    Harper, J. T. & Humphrey, N. F. Borehole video analysis of a temperate glacier’s englacial and subglacial structure: implications for glacier flow models. Geology 23, 901–904 (1995)

    Google Scholar 

  19. 19

    Pohjola, V. A. TV-video observations of englacial voids in Storglaciaren, Sweden. J. Glaciol. 40, 231–240 (1994)

    Google Scholar 

  20. 20

    Harper, J. T., Humphrey, N. F., Pfeffer, W. T. & Lazar, B. Two modes of accelerated glacier sliding related to water. Geophys. Res. Lett. 34 10.1029/2007GL030233 (2007)

  21. 21

    Boon, S. & Sharp, M. The role of hydrologically-driven ice fracture in drainage system evolution on an Arctic glacier. Geophys. Res. Lett. 30 10.1029/2003GL018034 (2003)

  22. 22

    Das, S. B. et al. Fracture propagation to the base of the Greenland Ice Sheet during supraglacial lake drainage. Science 320, 778–781 (2008)

    CAS  Google Scholar 

  23. 23

    Krawczynski, M. J., Behn, M. D., Das, S. B. & Joughin, I. Constraints on the lake volume required for hydro-fracture through ice sheets. Geophys. Res. Lett. 36 10.1029/2008GL036765 (2009)

  24. 24

    Fountain, A. G., Jacobel, R. W., Schlichting, R. & Jansson, P. Fractures as the main pathways of water flow in temperate glaciers. Nature 433, 618–621 (2005)

    CAS  Google Scholar 

  25. 25

    Clarke, T., Liu, C., Lord, N. & Bentley, C. Evidence for a recently abandoned shear margin adjacent to ice stream B2, Antarctica, from ice-penetrating radar measurements. J. Geophys. Res. 105, 13,406–13,422 (2000)

    Google Scholar 

  26. 26

    Ensminger, S. L., Alley, R. B., Evenson, E. B., Lawson, D. E. & Larson, G. J. Basal-crevasse-fill origin of laminated debris bands at Matanuska Glacier, Alaska, USA. J. Glaciol. 47, 412–422 (2001)

    CAS  Google Scholar 

  27. 27

    Woodward, J., Murray, T. & McCaig, A. Formation and reorientation of structure in the surge-type glacier Kongsvegen, Svalbard. J. Quat. Sci. 17, 201–209 (2002)

    Google Scholar 

  28. 28

    Lingle, C. S. & Fatland, D. R. Does englacial water storage drive temperate glacier surges? Ann. Glaciol. 36, 14–20 (2003)

    Google Scholar 

Download references


This work was funded by the US National Science Foundation Office of Polar Programs, Arctic Natural Sciences.

Author information




All authors contributed to developing the ideas presented. J.T.H. and T.W.M. conducted drilling and borehole experiments using drilling equipment designed by N.F.H. J.H.B. carried out radar and seismic experiments. J.T.H. drafted the manuscript, with all authors contributing to it.

Corresponding author

Correspondence to Joel T. Harper.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1-6 with legends, Supplementary Table 1 and additional references. (PDF 898 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Harper, J., Bradford, J., Humphrey, N. et al. Vertical extension of the subglacial drainage system into basal crevasses. Nature 467, 579–582 (2010).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.