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

Yuan Li,Maohuan Huang,Sepp Kipfstuhl

doi:10.3390/cryst7040097

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.

Highlights

IntroductionThe ensemble of c-axis orientations (the c-axis of each grain points in a direction given by a unit →vector c within a mass of polycrystalline ice) constitutes the c-axis fabric of the ice, sometimes referred to as orientation fabric, or ‘fabric’ [1]
The ensemble of c-axis orientations constitutes the c-axis fabric of the ice, sometimes referred to as orientation fabric, or ‘fabric’ [1]
The mean grain size of polycrystalline ice increases over time by grain growth in the absence of mechanisms to form new grains [1], i.e., the Normal Grain Growth (NGG) depends upon the migration which is driven by curvature of the boundaries in slowly deforming ice

Summary

Introduction

The ensemble of c-axis orientations (the c-axis of each grain points in a direction given by a unit →vector c within a mass of polycrystalline ice) constitutes the c-axis fabric of the ice, sometimes referred to as orientation fabric, or ‘fabric’ [1]. Some micro-processes, such as lattice dislocation, intra-grain sliding, and diffusion creep with respect to the temperature of ice since its formation can be used to deduce inversely the paleo-air-temperature, ice-flow control laws, c-axis fabrics, and grain sizes. For this reason, constructing the relationship between the evolution of microstructure and fabric and climate change [6,7,8,9,10,11,12,13] is meaningful work, even though it is challenging and complex.

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Discussion

Conclusion