Temperature and strain controls on ice deformation mechanisms: insights from the microstructures of samples deformed to progressively higher strains at −10, −20 and −30 °C

• Published in: The Cryosphere
• Main Authors: S. Fan, T. F. Hager, D. J. Prior, A. J. Cross, D. L. Goldsby, C. Qi, M. Negrini, J. Wheeler
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2020
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-14-3875-2020; https://doaj.org/article/3cb50feea3b148cf9b620080dbd9311a

In order to better understand ice deformation mechanisms, we document the microstructural evolution of ice with increasing strain. We include data from experiments at relatively low temperatures ( −20 and −30 ∘ C), where the microstructural evolution with axial strain has never before been documented. Polycrystalline pure water ice was deformed under a constant displacement rate (strain rate <math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∼</mo><mn mathvariant="normal">1.0</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="61pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="70dcb4f99f203b8abffe7bb413ebd79e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-14-3875-2020-ie00001.svg" width="61pt" height="13pt" src="tc-14-3875-2020-ie00001.png"/></svg:svg> s −1 ) to progressively higher strains ( ∼ 3 %, 5 %, 8 %, 12 % and 20 %) at temperatures of −10 , −20 and −30 ∘ C. Microstructural data were generated from cryogenic electron backscattered diffraction (cryo-EBSD) analyses. All deformed samples contain subgrain (low-angle misorientations) structures with misorientation axes that lie dominantly in the basal plane, suggesting the activity of dislocation creep (glide primarily on the basal plane), recovery and subgrain rotation. Grain boundaries are lobate in all experiments, suggesting the operation of strain-induced grain boundary migration (GBM). Deformed ice samples are characterized by interlocking big and small grains and are, on average, finer grained than undeformed samples. Misorientation analyses between nearby grains in 2-D EBSD maps are consistent with some 2-D grains being different limbs of the same irregular grain in the 3-D volume. ...