Ice Microstructure and Fabric of Guliya Ice Cap in Tibetan Plateau, and Comparisons with Vostok3G-1, EPICA DML, and North GRIP

Abstract

This work is the first in the general natural ice literature to compare microstructures and fabrics of continent-type mountain ice in mid-low latitudes with polar ice in order to find out how they evolved based on similar fabric patterns of their vertically girdles. Microstructures and fabrics along the Guliya ice core on the Tibetan Plateau, China, were measured at a depth interval of approximately 10 m. The grain sizes increase unevenly with depth. The fabric patterns vary from the isotropic fabric, to broad single maximum, to vertical girdle, to single-maximum, and finally to multiple-maximum fabric. The grain growth rate of the Guliya core is faster than that of the Vostok3G-1, the EPICA DML, and the North GRIP. The vertical girdle fabric of the Guliya core forms at a high temperature and low strain rate. The strong single maximum fabric of the Guliya core appears in the mid-low part of the core with vertical uniaxial compression or simple shear. The thermal kinemics caused by the temperature can play a vital role in different stress cases to cast the similar or same fabric patterns. Normal grain growth, polygonization/rotation recrystallization, and migration recrystallization play roles different importance at different depths.

Full crystallographic orientation (<i>c</i> and <i>a</i> axes) of warm, coarse-grained ice in a shear-dominated setting: a case study, Storglaciären, Sweden

“…ron and Langway, 1982;Herron et al, 1985;Langway et al, 1988;Thorsteinsson, 1997;Gow et al, 1997;Wang et al, 2002;Svensson et al, 2003b;. Studying microstructures in ice sheets offers the advantages of examining an extensive record of ice deforming under relatively simple kinematic conditions.…”

“…Ice with the multimaxima CPO in valley glaciers (Rigsby, 1951;Meier et al, 1954;Kamb, 1959;Higashi, 1967;Jonsson, 1970;Fabre, 1973;Vallon et al, 1976;Tison and Hubbard, 2000;Hellmann et al, in review) and deep in ice sheets (Gow and Williamson, 1976;Matsuda and Wakahama, 1978;Russell-Head and Budd, 1979;Gow et al, 1997;Diprinzio et al, 2005;Gow and Meese, 2007;Fitzpatrick et al, 2017;Li et al, 2017) consists of large, branched crystals that lack undulose extinction and have irregular, lobate grain boundaries (Figs. 2a and 3).…”

“…Nonetheless, there remains the uncertainty about whether the maxima are truly distinct or reflect repeated measurements of individual grains. It might be noted that in recent work little or no explicit attention is given to the problem of sample size in coarse-grained ice (see Dahl-Jensen et al, 2013;Fitzpatrick et al, 2014;Li et al, 2017) and to the significance of possible island grains on fabric (see Diprinzio et al, 2005;Gow and Meese, 2007;Dahl-Jensen et al, 2013;Fitzpatrick et al, 2014;Li et al, 2017). This problem may not have been highlighted, as CPO in coarse-grained ice was not the sole focus of these ice core studies.…”