Natureandbehaviorofdislocationsinice.PDFVIP

Title Author(s)Hondoh, Takeo CitationPhysics of Ice Core Records: 3-24 Issue Date2000 DOI Doc URL /2115/32459 Right Type proceedings Additional Information File P3-24.pdf Information Instructions for use 3 Nature and behavior of dislocations in ice Takeo Hondoh Institute of Low Temperature Science, Hokkaido University, N19W8, Sapporo 060-0819, JAPAN Abstract: To better understand various phenomena related to ice-core records, the properties of lattice defects in ice, particularly dislocations, are reviewed. The plasticity of ice significantly affects ice sheet dynamics and ice-core dating. It is well known that ice is predominantly deformed by the basal slip system 11 2 0/(0001): all nonbasal slip systems are inactive. In particular, the slip systems observed until now are not responsible for uniaxial deformation parallel to the c-axis. However, in spite of difficulties in the nonbasal slip systems, the velocities of dislocations moving on nonbasal planes 11 20/{l0 1 O} or 112 0/{l0 1 I} are larger than those on the basal plane. Possible mechanisms for the non- basal slips are discussed in light of recent studies of dislocations in ice. The peculiar nature of ice plasticity is explained by characteristic structures of dislocations in ice, which are responsible for this crystallographic anisotropy. Dislocations in ice are stabilized by dissociation into two partial dislocations owing to the very low energy of stacking faults lying on the basal plane. Therefore, dislocations in ice have a ribbon-like structure extended on the basal plane so that dislocation motion in ice is restricted to the basal planes. Because of this