Two modes of accelerated glacier sliding related to water

  • Harper J
  • Humphrey N
  • Pfeffer W
 et al. 
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Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L12503, doi:10.1029/2007GL030233, 2007 Two modes of accelerated glacier sliding related to water Joel T. Harper Department of Geosciences, University of Montana, Missoula, Montana, USA Neil F. Humphrey Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming, USA W. Tad Pfeffer Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, USA Brian Lazar Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, USA Abstract We present the first glacier-wide detailed measurement of basal effective pressure and related observations including bed separation to elucidate the role of water in sliding. The hard bedded glacier instrumented in our study exhibited two phases of accelerated sliding motion apparently driven by separate mechanisms. The first acceleration phase (up to 5 fold increase in speed) was closely tied to an increase in bed separation. The faster second phase (up to 9 fold increase in speed) was related to an unusually high level of connectivity of subglacial waters. We infer the first mode was related to cavity opening and the second mode was related to reduced ice contact with the bed. Glacier sliding over a hard bed is typically represented by sliding laws that include the effective basal pressure, but neither sliding phase was accompanied by a simultaneous decrease in local or regional effective pressure. Received 31 March 2007; accepted 29 May 2007; published 29 June 2007. Keywords: glacier sliding; subglacial hydrology; glacier flow dynamics. Index Terms: 0766 Cryosphere: Thermodynamics (1011, 3611, 8411); 0720 Cryosphere: Glaciers; 1863 Hydrology: Snow and ice (0736, 0738, 0776, 1827); 1822 Hydrology: Geomechanics. Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 250189 bytes) Citation: Harper, J. T., N. F. Humphrey, W. T. Pfeffer, and B. Lazar (2007), Two modes of accelerated glacier sliding related to water, Geophys. Res. Lett., 34, L12503, doi:10.1029/2007GL030233

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Authors

  • Joel T. Harper

  • Neil F. Humphrey

  • W. Tad Pfeffer

  • Brian Lazar

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