Three-dimensional deformation measured in an Alaskan glacier

Science

Volumn 281, Issue 5381, 1998, Pages 1340-1342

  Harper, Joel T ^a   Humphrey, Neil F ^a   Pfeffer, W Tad ^b  

^a UNIVERSITY OF WYOMING   (United States)

^b UNIVERSITY OF COLORADO   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ICE;

DEFORMATION; GLACIER FLOW; STRAIN;

ARTICLE; CLIMATE; GEOLOGY; PRIORITY JOURNAL; SEASON; STRESS; VELOCITY;

ALASKA; UNITED STATES; WORTHINGTON GLACIER;

EID: 0032575734     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.281.5381.1340     Document Type: Article

References (22)

1. J. F. Nye, R. Soc. London Proc. Ser. A 219, 477 (1953); R. LeB Hooke, Rev. Geophys. Space Phys. 19, 664 (1981); C. J. van der Veen and I. M. Whillans, J. Glaciol. 36, 324 (1990).
2. J. F. Nye, R. Soc. London Proc. Ser. A 219, 477 (1953); R. LeB Hooke, Rev. Geophys. Space Phys. 19, 664 (1981); C. J. van der Veen and I. M. Whillans, J. Glaciol. 36, 324 (1990).
3. J. F. Nye, R. Soc. London Proc. Ser. A 219, 477 (1953); R. LeB Hooke, Rev. Geophys. Space Phys. 19, 664 (1981); C. J. van der Veen and I. M. Whillans, J. Glaciol. 36, 324 (1990).
4. Examples include velocity variations occurring over months to weeks [R. LeB Hooke, P. Calla, et al., J. Glaciol. 35, 235 (1989)] and days to hours [A. Iken and R. A. Bindschadler, ibid. 32, 101 (1986)].
5. Examples include velocity variations occurring over months to weeks [R. LeB Hooke, P. Calla, et al., J. Glaciol. 35, 235 (1989)] and days to hours [A. Iken and R. A. Bindschadler, ibid. 32, 101 (1986)].
6. S. M. Hodge, ibid. 13, 349 (1974); B. Kamb et al., J. Geophys. Res. 99, 15231 (1994); J. Harbor et al., Geology 25, 739 (1997).
7. S. M. Hodge, ibid. 13, 349 (1974); B. Kamb et al., J. Geophys. Res. 99, 15231 (1994); J. Harbor et al., Geology 25, 739 (1997).
8. S. M. Hodge, ibid. 13, 349 (1974); B. Kamb et al., J. Geophys. Res. 99, 15231 (1994); J. Harbor et al., Geology 25, 739 (1997).
9. A dense array of radio-echo sounding measurements were processed with three-dimensional migration techniques. Comparisons of these measurements with bore-hole observations suggest that the radar is accurate to within about 8.5 m (B. C. Welch, W. T. Pfeffer, J. T. Harper, N. F. Humphrey, J. Glaciol., in press).
10. J. T. Harper and N. F. Humphrey, Geology 23, 901 (1995).
11. M. F. Meier, U.S. Geol. Surv. Prof. Pap. 351 (1960); W. S. B. Paterson and J. C. Savage, J. Geophys. Res. 68, 4537 (1963); C. F. Raymond, J. Glaciol. 10, 55 (1971); R. LeB. Hooke, P. Holmlund, N. R Iverson, ibid. 33, 72 (1987) were all forced to smooth inclinometry data because of high levels of noise.
12. M. F. Meier, U.S. Geol. Surv. Prof. Pap. 351 (1960); W. S. B. Paterson and J. C. Savage, J. Geophys. Res. 68, 4537 (1963); C. F. Raymond, J. Glaciol. 10, 55 (1971); R. LeB. Hooke, P. Holmlund, N. R Iverson, ibid. 33, 72 (1987) were all forced to smooth inclinometry data because of high levels of noise.
13. M. F. Meier, U.S. Geol. Surv. Prof. Pap. 351 (1960); W. S. B. Paterson and J. C. Savage, J. Geophys. Res. 68, 4537 (1963); C. F. Raymond, J. Glaciol. 10, 55 (1971); R. LeB. Hooke, P. Holmlund, N. R Iverson, ibid. 33, 72 (1987) were all forced to smooth inclinometry data because of high levels of noise.
14. M. F. Meier, U.S. Geol. Surv. Prof. Pap. 351 (1960); W. S. B. Paterson and J. C. Savage, J. Geophys. Res. 68, 4537 (1963); C. F. Raymond, J. Glaciol. 10, 55 (1971); R. LeB. Hooke, P. Holmlund, N. R Iverson, ibid. 33, 72 (1987) were all forced to smooth inclinometry data because of high levels of noise.
15. The instrument was constructed by Slope Indicator Canada, Ltd. (Vancouver, BC). Measurement errors associated with a prototype of this instrument are discussed by E. W. Blake and G. K. C. Clarke [J. Glaciol. 38, 113 (1992)]. However, analysis of actual data from the instrument used suggests that instrument errors are slightly improved from manufacturer specifications [J. T. Harper, thesis, University of Wyoming (1997); S. V. Huzurbazar, unpublished material]. Additionally, the uniformity of the borehole walls enabled a high degree of repeat-ability for the measurements.
16. The instrument was constructed by Slope Indicator Canada, Ltd. (Vancouver, BC). Measurement errors associated with a prototype of this instrument are discussed by E. W. Blake and G. K. C. Clarke [J. Glaciol. 38, 113 (1992)]. However, analysis of actual data from the instrument used suggests that instrument errors are slightly improved from manufacturer specifications [J. T. Harper, thesis, University of Wyoming (1997); S. V. Huzurbazar, unpublished material]. Additionally, the uniformity of the borehole walls enabled a high degree of repeat-ability for the measurements.
17. The instrument was constructed by Slope Indicator Canada, Ltd. (Vancouver, BC). Measurement errors associated with a prototype of this instrument are discussed by E. W. Blake and G. K. C. Clarke [J. Glaciol. 38, 113 (1992)]. However, analysis of actual data from the instrument used suggests that instrument errors are slightly improved from manufacturer specifications [J. T. Harper, thesis, University of Wyoming (1997); S. V. Huzurbazar, unpublished material]. Additionally, the uniformity of the borehole walls enabled a high degree of repeat-ability for the measurements.
18. We follow the method of C. F Raymond, J. Glaciol. 10, 39 (1971).
19. We use a cubic spline function with an iterative scheme designed to minimize the curvature of the function between data points [I. C. Briggs, Geophysics 1974, 39 (1974)]. This interpolation was tested extensively with synthetic data.
20. J. T. Harper, N. F. Humphrey, W. T. Pfeffer, B. C. Welch, U.S. Army Cold Reg. Res. Eng. Lab. Spec. Rep. 96-27 (1996), p. 41.
21. This measurement was made within the same reach and time of year as the deformation experiments, but during a subsequent year. Sliding and surface velocities were determined by continuous filming of the base of a borehole with concurrent surveying of velocity at the surface.
22. Funded by grants from NSF (OPP-9122966 to N.F.H. and OPP-9122916 to W.T.P.). Additional funding for computer visualization was provided by NSF's EPSCoR (Experimental Program to Stimulate Competitive Research) program (EPS9550477), through the University of Wyoming's Spatial Data and Visualization Center project. D. Bahr, B. Welch, and B. Raup all made significant contributions to portions of the work presented here.