Preprints
https://doi.org/10.5194/tc-2021-336
https://doi.org/10.5194/tc-2021-336
 
30 Nov 2021
30 Nov 2021
Status: a revised version of this preprint was accepted for the journal TC and is expected to appear here in due course.

Development of crystal orientation fabric in the Dome Fuji ice core in East Antarctica: implications for the deformation regime in ice sheets

Tomotaka Saruya1, Shuji Fujita1,2, Yoshinori Iizuka3, Atsushi Miyamoto4, Hiroshi Ohno5, Akira Hori5, Wataru Shigeyama2,a, Motohiro Hirabayashi1, and Kumiko Goto-Azuma1,2 Tomotaka Saruya et al.
  • 1National Institute of Polar Research, Tokyo 190-8518, Japan
  • 2Department of Polar Science, The Graduate University for Advanced Studies, SOKENDAI, Tokyo 190-8518, Japan
  • 3Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan
  • 4Institute for the Advancement of Higher Education, Hokkaido University, Sapporo 060-0817, Japan
  • 5Kitami Institute of Technology, Kitami 090-8507, Japan
  • anow at: JEOL Ltd., Tokyo 196-8558, Japan

Abstract. The crystal orientation fabric (COF) of a polar ice sheet has a significant effect on the rheology of the sheet. With the aim of better understanding the deformation regime of ice sheets, the present work investigated the COF in the upper 80 % of the depth within the 3035 m long Dome Fuji Station ice core drilled at one of the dome summits in East Antarctica. Dielectric anisotropy (∆ε) data were acquired as a novel indicator of the vertical clustering of COF resulting from vertical compressional strain within the dome, at which the ice cover has an age of approximately 300 kyrs BP. The ∆ε values were found to exhibit a general increase moving in the depth direction, but with fluctuations over distances on the order of 10–102 m. In addition, significant decreases in ∆ε were found to be associated with depths corresponding to three major glacial to interglacial transitions. These changes in ∆ε are ascribed to variations in the deformational history caused by dislocation motion occurring from near-surface depths to deeper layers. Fluctuations in ∆ε over distances of less than 0.5 m exhibited a strong inverse correlation with at depths greater than approximately 1200 m, indicating that they were enhanced during the glacial/interglacial transitions. The ∆ε data also exhibited a positive correlation with the concentration of chloride ions together with an inverse correlation with the amount of dust particles in the ice core at greater depths corresponding to decreases in the degree of c-axis clustering. Finally, we found that fluctuations in ∆ε persisted to approximately 80 % of the total depth of the ice sheet. These data suggest that the factors determining the deformation of ice include the concentration of chloride ions and amount of dust particles, and that the layered contrast associated with the COF is preserved all the way from the near-surface to a depth corresponding to approximately 80 % of the thickness of the ice sheet. These findings provide important implications regarding further development of the COF under the various stress-strain configurations that the ice will experience in the deepest region, approximately 20 % of the total depth from the ice/bed interface.

Tomotaka Saruya et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-336', Anonymous Referee #1, 24 Jan 2022
    • AC1: 'Reply on RC1', Tomotaka Saruya, 03 Feb 2022
  • RC2: 'Comment on tc-2021-336', Anonymous Referee #2, 14 Mar 2022
    • AC2: 'Reply on RC2', Tomotaka Saruya, 28 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-336', Anonymous Referee #1, 24 Jan 2022
    • AC1: 'Reply on RC1', Tomotaka Saruya, 03 Feb 2022
  • RC2: 'Comment on tc-2021-336', Anonymous Referee #2, 14 Mar 2022
    • AC2: 'Reply on RC2', Tomotaka Saruya, 28 Mar 2022

Tomotaka Saruya et al.

Tomotaka Saruya et al.

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Short summary
Crystal orientation fabrics (COF) of the Dome Fuji ice core was investigated with an innovative method with unprecedentedly high statistical significance and dense depth coverage. COF profile and its fluctuation were found to be highly dependent on concentration of chloride ion and dust. The data suggest deformation of ice at the deepest zone will be highly influenced by COF fluctuations that progressively develop from the near-surface firn toward the deepest zone within ice sheets.