Sonic methods for measuring crystal orientation fabric in ice, and results from the West Antarctic ice sheet (WAIS) Divide

Dan Kluskiewicz, Edwin D. Waddington, Sridhar Anandakrishnan, Donald E. Voigt, Kenichi Matsuoka, Michael P. McCarthy

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

We describe methods for measuring crystal orientation fabric with sonic waves in an ice core borehole, with special attention paid to vertical-girdle fabrics that are prevalent at the WAIS Divide. The speed of vertically propagating compressional waves in ice is influenced by vertical clustering of the ice crystal c-axes. Shear-wave speeds - particularly the speed separation between fast and slow shear polarizations - are sensitive to azimuthal anisotropy. Sonic data from the WAIS Divide complement thin-section measurements of fabric. Thin sections show a steady transition to strong girdle fabrics in the upper 2000 m of ice, followed by a transition to vertical-pole fabrics below 2500 m depth. Compressional-wave sonic data are inconclusive in the upper ice, due to noise, as well as the method's inherent insensitivity to girdle fabrics. Compared with available thin sections, sonic data provide better resolution of the transition to pole fabrics below 2500 m, notably including an abrupt increase in vertical clustering near 3000 m. Our compressional-wave measurements resolve fabric changes occurring over depth ranges of a few meters that cannot be inferred from available thin sections, but are sensitive only to zenithal anisotropy. Future logging tools should be designed to measure shear waves in addition to compressional waves, especially for logging in regions where ice flow patterns favor the development of girdle fabrics.

Original languageEnglish (US)
Pages (from-to)603-617
Number of pages15
JournalJournal of Glaciology
Volume63
Issue number240
DOIs
StatePublished - Aug 1 2017

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ice sheet
crystal
ice
thin section
S-wave
anisotropy
measuring
fabric
method
ice flow
ice crystal
ice core
flow pattern
polarization
borehole
speed

All Science Journal Classification (ASJC) codes

  • Earth-Surface Processes

Cite this

Kluskiewicz, Dan ; Waddington, Edwin D. ; Anandakrishnan, Sridhar ; Voigt, Donald E. ; Matsuoka, Kenichi ; McCarthy, Michael P. / Sonic methods for measuring crystal orientation fabric in ice, and results from the West Antarctic ice sheet (WAIS) Divide. In: Journal of Glaciology. 2017 ; Vol. 63, No. 240. pp. 603-617.
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Sonic methods for measuring crystal orientation fabric in ice, and results from the West Antarctic ice sheet (WAIS) Divide. / Kluskiewicz, Dan; Waddington, Edwin D.; Anandakrishnan, Sridhar; Voigt, Donald E.; Matsuoka, Kenichi; McCarthy, Michael P.

In: Journal of Glaciology, Vol. 63, No. 240, 01.08.2017, p. 603-617.

Research output: Contribution to journalArticle

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