INVESTIGATION OF PALEOCLIMATE AND FLOW HISTORY OF ICE SHEET BY ICE CRYSTAL EVOLUTION MODEL IN ICE SHEET

本项目的目标是：1)研究冰中化学杂质的行为及其与晶界迁移的相互作用，以及杂质对冰力学性能的影响；2)利用我们开发的晶体结构演化模型，开发从冰芯晶体结构和织物数据中获取古气候和冰盖流动历史信息的方法。我们进行了晶粒生长/再结晶实验和人工生长冰的力学试验，得到了以下结果：建立了细晶（约等于100微米）、低浓度化学杂质均匀分布的冰样制备技术。得到了冰晶界迁移速率的温度依赖关系和杂质浓度依赖关系。在超过ppms的高杂质浓度和高温（>-5℃）条件下，含杂质的冰比纯冰更软。我们发现了冰晶小角度边界形成时晶体变形和c轴旋转的行为。考虑到上述发现，我们将开发我们的晶体结构演化模型。

The objectives of this project are 1) investigation of the behavior of chemical impurities in ice and its interaction with grain boundary migration and the effect of impurities on mechanical properties of ice, and 2) development of the method that can derive the information about paleoclimate and ice sheet flow history from ice core crystal texture and fabric data by using the crystal texture evolution model developed by us. We conducted the grain growth/recrystallization experiments and the mechanical tests with artificial grown ice and obtained following results.1.We established the techniques that produce the ice samples with fine crystal (【approximately equal】100um) and homogeneous distribution of low concentration chemical impurities.2.We obtained the temperature dependence and impurity concentration dependence of grain boundary migration rate of ice.3.In the regime of high impurity concentration more than ppms and high temperature (>-5 degree C) the ice contained impurity become softer than pure ice.4.We found the behaviors of crystal deformation and c-axis rotation when the small angle boundary formation in ice crystals.We will develop our crystal texture evolution model taking account the findings above.