Modelling of deformtion and recrystallisation microstructures in polar ice

了解极地冰的变形机制对于预测极地冰盖的流动及其对全球气候的影响至关重要。冰的变形也会影响地球上最好的气候记录之一：在深冰芯中观察到的单个冰层。微结构通过揭示冰盖流动过程中的变形过程，形成了原位变形的主要记录。AWI开发的新的微观结构分析技术现在可以比以往任何时候都更详细和广泛地评估这些微观结构。在这个项目中，已经开始使用综合建模平台Elle对冰的微观结构进行数值建模。在更新和改进算法后，Elle现在能够模拟极地冰中发生的几个主要过程：再结晶，晶粒生长和晶体塑性变形。在该项目剩余的26个月1中，现有的两相材料程序将适用于模拟带有气泡或笼形物的冰，并模拟晶内恢复。系统模拟的结果将与理论分析和AWI提供的几个积雪和冰芯（特别是EPICA-DML深冰芯）的独特微结构数据集进行定量比较。特别是，我们将批判性地重新评估晶界的形成和迁移的作用，不断改造的微观结构。该项目的成果将增进我们对极地冰的机械行为的了解，并改进对气候记录的分析，这对冰盖和气候建模至关重要。

Knowledge of the deformation mechanisms of polar ice is of crucial importance to predict the flow of polar ice caps and hence their influence on the global climate. Deformation of ice also impacts on one of the best climate record on Earth: the individual ice layers observed in deep ice cores. Microstructures form the main record of in situ deformation, by revealing the deformation processes that operate during the flow of an ice sheet. New microstructural analysis techniques developed at AWI now allow a much more detailed and extensive assessment of these microstructures than ever before. Within this project, a start has been made with the numerical modelling of ice microstructures, using the comprehensive modelling platform Elle . After updating and refining algorithms, Elle is now capable of simulating several of the main processes that occur in polar ice: recrystallisation, grain growth and crystal-plastic deformation. In the course of the project s remaining 26 months1 existing routines for two-phase materials will be adapted to model ice with bubbles or clathrates, and to model intracrystalline recovery. Results of systematic simulations will be compared quantitatively with theoretical analyses and the unique microstructure dataset available at AWI of several firn and ice cores (especially the EPICA–DML deep ice core). In particular we will critically reassess the role of grain boundary formation and migration that continually reworks the microstructure. The results of this project will improve our knowledge of the mechanical behaviour of polar ice and refine the analysis of climatic records, which are essential to ice sheet and climate modelling.