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  • 标题:In situ measurements of till deformation and water pressure
  • 本地全文:下载
  • 作者:Martin Truffer ; William D. Harrison
  • 期刊名称:Journal of Glaciology
  • 印刷版ISSN:0022-1430
  • 电子版ISSN:1727-5652
  • 出版年度:2006
  • 卷号:52
  • 期号:177
  • 页码:175-182
  • DOI:10.3189/172756506781828700
  • 出版社:Cambridge University Press
  • 摘要:A newly developed hammer was used to insert two autonomous probes 0.8 m and 2.1 m into clast-rich subglacial till under Black Rapids Glacier, Alaska, USA. Both probes were instrumented with a dual-axis tilt sensor and a pore-water pressure transducer. The data are compared to a 75 day record of surface velocities. Till deformation at depth was found to be highly seasonal: it is significant during an early-season speed-up event, but during long periods thereafter measured till deformation rates are negligible. Both tilt records show rotation around the probe axis, which indicates a change in tilt direction of about 30°. The tilt records are very similar, suggesting spatial homogeneity on the scale of the probe separation (4 m horizontal and 3.3 m vertical). There is evidence that during much of the year sliding of ice over till or deformation of a thin till layer (<20 cm) accounts for at least two-thirds of total basal motion. Basal motion accounts for 50–70% of the total surface motion. The inferred amount of ice–till sliding is larger than that found at the same location in a previous study, when surface velocities were about 10% lower. We suggest that variations in ice–till coupling account for the observed variations in mean annual speed.
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