Deformation of ice on the grain scale by means of high-resolution crystal-orientation measurements using X-ray Laue and Electron backscatter diffraction

• Applicant: Professorin Dr. Ilka Weikusat
• Subject Area: Oceanography
• Term: from 2008 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 75773225

• Final Report Year: 2014

Final Report Abstract

The project ”Deformation of ice on the grain scale by means of high-resolution crystalorientation measurements” applied X-ray Laue diffraction and Electron backscattered diffraction on Antarctic ice samples in combination with standard microstructural techniques such as light-microsopy microstructure mapping. For both diffraction methods transfer procedures have been developed. For EBSD, surface-preserving conditions within the high vacuum of the SEM and their theoretical understanding involving a vapour-solid phase diagram are proposed. Subgrain boundary types have been characterized making use of topological and crystallographic geometries revealing basal twist and tilt boundaries, as well as non-basal tilt boundaries as end members; filled with mixed boundaries. Statistics on these findings suggest, that non-basal dislocations indeed play a significant role in ice. Furthermore, the importance of dynamic recrystallization, esp. rotation recrystallization and strain-induced boundary migration, control the microstructure of natural polar ice. New microphysical-process modelling approaches including the anisotropic deformation of ice as well as recrystallization mechanisms are developed and applied in following projects.

Publications

• Deformation Microstructures in an Antarctic Ice Core (EDML) and in Experimentally Deformed Artificial Ice. Physics of Ice Core Records II, Supplement Issue of Low Temperature Science, Vol. 68, 2009, 2, 115-123
  Weikusat, I.; Kipfstuhl, S.; Azuma, N.; Faria, S. H. & Miyamoto, A.
  
• Subgrain boundaries and related microstructural features in EPICA-Dronning Maud Land (EDML) deep ice core. J. Glaciology 55, 2009, 461-472
  Weikusat, I.; Kipfstuhl, S.; Faria, S. H.; Azuma, N. & Miyamoto, A.
  (See online at https://doi.org/10.3189/002214309788816614)
• Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM. J. Microscopy 242, 2010, 295-310
  Weikusat, I.; de Winter, D. A. M.; Pennock, G. M.; Hayles, M.; Schneijdenberg, C. T. W. M. & Drury, M. R.
  (See online at https://doi.org/10.1111/j.1365-2818.2010.03471.x)
• Competition between grain growth and grain-size reduction in polar ice. J. Glaciology 57, 2011, 942-948
  Rössiger, J.; Bons, P. D.; Griera, A.; Jessell, M. W.; Evans, L.; Montagnat, M.; Kipfstuhl, S.; Faria, S. H. & Weikusat, I.
  (See online at https://doi.org/10.3189/002214311798043690)
• Complete determination of ice crystal orientation and microstructure investigation on ice core samples enabled by a new X-ray Laue diffraction method. J. Glaciology 57, 2011, 67-74
  Miyamoto, A.; Weikusat, I. & Hondoh, T.
  (See online at https://doi.org/10.3189/002214311795306754)
• Subgrain boundaries in Antarctic ice quantified by X-ray Laue diffraction. J. Glaciology 57, 2011, 85-94
  Weikusat, I.; Miyamoto, A.; Faria, S. H.; Kipfstuhl, S.; Azuma, N. & Hondoh, T.
  (See online at https://doi.org/10.3189/002214311795306628)
• The Microstructure of Polar Ice. Part I: Highlights from ice core research. J. Structural Geology 61, 2014, 2-20
  Faria, S. H.; Weikusat, I. & Azuma, N.
  (See online at https://doi.org/10.1016/j.jsg.2013.09.010)
• The Microstructure of Polar Ice. Part II: State of the Art. J. Structural Geology 61, 2014, 21-49
  Faria, S. H.; Weikusat, I. & Azuma, N.
  (See online at https://doi.org/10.1016/j.jsg.2013.11.003)