Distribution and chemistry of micro-inclusions in the EPICA-DML deep ice core

在南极洲钻探了深厚的冰芯，目的是重建过去100万年来地球气候的历史。然而，对古气候记录的解释严重纠结于常年的化学反应、混合和扩散过程，涉及限制在极地冰层中的许多有价值的气候指标。在这方面，特别关键的是形成“黑点”和微泡等微包裹体，以及可能在三重结合处形成的酸性溶液脉络。尽管前者丰富，并对以后者为代表的气候记录构成威胁，但人们对它们知之甚少。在这个项目中，我们计划研究从南极Dronning Maud陆地提取的超过2.7公里长的EPICA-DML深部冰芯中微包裹体的化学、分布、频率和演化(松弛)。为了完成这项具有挑战性的任务，我们计划将光学显微镜的自动化方法和用于统计研究的数字图像处理方法结合起来，称为微结构映射(μSM)，以及通过微焦点拉曼光谱(μRS)和扫描电子显微镜(CRYO-SEM)结合能量色散X射线光谱(CRYO-EDS)和电子背散射衍射(CRYO-EBSD)的集成微观化学分析。这项研究的结果不仅将解决微包裹体的性质和液脉的赋存问题，而且还将为在调查过程中开发新的南极冰中溶解气体和离子扩散模型提供基础。

Deep ice cores have been drilled in Antarctica with the aim at reconstructing the history of Earth’s climate in the last million years. However, the interpretation of paleoclimatic records is severely entangled by perennial chemical reactions, mixing and diffusion processes involving many of the valuable climate proxies confined in polar ice. Particularly critical in this respect is the formation of micro-inclusions such as “black dots” and micro-bubbles, as well as possible veins of acid solutions at triple junctions. In spite of the abundance of the former and the menace to climate records represented by the latter, very little is known about them. We propose in this project to investigate the chemistry, distribution, frequency and evolution (relaxation) of micro-inclusions throughout the more than 2.7 km long EPICA-DML deep ice core extracted from Dronning Maud Land, Antarctica. In order to accomplish this challenging task we plan to combine an automated method of optical microscopy and digital image processing for statistical investigations called microstructure mapping (μSM) with an integrated micro-chemical analysis via micro-focus Raman spectrometry (μRS) and scanning electron microscopy (cryo-SEM) coupled with energy-dispersive X-ray spectroscopy (cryo-EDS) and electron backscatter diffraction (cryo-EBSD). The results of this study shall not only resolve the question about the nature of micro-inclusions and the occurrence of liquid veins but also serve as basis for new models of diffusion of dissolved gases and ions in Antarctic ice, to be developed in the course of the investigations.