Location and distribution of micro-inclusions in the EDML and NEEM ice cores using optical microscopy and in situ Raman spectroscopy
Location and distribution of micro-inclusions in the EDML and NEEM ice cores using optical microscopy and in situ Raman spectroscopy
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DOI：
10.5194/tc-11-1075-2017
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发表时间：
2017-05-05
期刊：
影响因子：
5.2
通讯作者：
Weikusat, Ilka
中科院分区：
文献类型：
--
作者：
Eichler, Jan;Kleitz, Ina;Weikusat, Ilka
杂质控制着极地冰的各种物理性质。它们的影响可以从微观结构的所有尺度上观察到（例如，粒度和取向）与冰盖流动行为（例如，井眼倾斜和关闭）。冰中的大多数杂质形成微米级的夹杂物。有人建议，这些亩夹杂物控制晶粒尺寸的多晶冰钉扎的晶界（齐纳钉扎），这应该反映在它们的分布相对于晶界网络。我们使用光学显微镜生成四个极地冰样品中微包裹体分布的高分辨率大比例尺地图（3 μ m pix（-1），8 x 2 cm（2））：两个来自南极洲（EDML，MIS 5.5），两个来自格陵兰岛（NEEM，全新世）。确定了5000多个μ包裹体的原位位置。一个拉曼显微镜被用来确认映射的夹杂物的样品比例的外在性质。二维晶界网络和μ夹杂物分布的叠加显示晶界和μ夹杂物之间没有显着的相关性。特别是，没有迹象表明晶界收获亩夹杂物可以被发现，也没有证据表明亩夹杂物抑制晶界迁移的慢模式钉扎可以被检测到。我们的理解冰的微观结构和流变学的杂质的影响的后果进行了讨论。
Impurities control a variety of physical properties of polar ice. Their impact can be observed at all scales from the microstructure (e.g., grain size and orientation) to the ice sheet flow behavior (e.g., borehole tilting and closure). Most impurities in ice form micrometer-sized inclusions. It has been suggested that these mu inclusions control the grain size of polycrystalline ice by pinning of grain boundaries (Zener pinning), which should be reflected in their distribution with respect to the grain boundary network. We used an optical microscope to generate high-resolution large-scale maps (3 mu m pix(-1), 8 x 2 cm(2)) of the distribution of micro-inclusions in four polar ice samples: two from Antarctica (EDML, MIS 5.5) and two from Greenland (NEEM, Holocene). The in situ positions of more than 5000 mu inclusions have been determined. A Raman microscope was used to confirm the extrinsic nature of a sample proportion of the mapped inclusions. A superposition of the 2-D grain boundary network and mu-inclusion distributions shows no significant correlations between grain boundaries and mu inclusions. In particular, no signs of grain boundaries harvesting mu inclusions could be found and no evidence of mu inclusions inhibiting grain boundary migration by slow-mode pinning could be detected. Consequences for our understanding of the impurity effect on ice microstructure and rheology are discussed.