Fabric measurement along the NEEM ice core, Greenland, and comparison with GRIP and NGRIP ice cores.
Fabric measurement along the NEEM ice core, Greenland, and comparison with GRIP and NGRIP ice cores.
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DOI：
10.5194/tcd-8-307-2014
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发表时间：
2014-04
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通讯作者：
M. Montagnat;N. Azuma;D. Dahl-Jensen;J. Eichler;S. Fujita;F. Gillet‐Chaulet;S. Kipfstuhl;D. Samyn;A. Svensson;I. Weikusat
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作者：
M. Montagnat;N. Azuma;D. Dahl-Jensen;J. Eichler;S. Fujita;F. Gillet‐Chaulet;S. Kipfstuhl;D. Samyn;A. Svensson;I. Weikusat
结构（分布的结晶取向）的配置文件沿着整个NEEM冰芯，格陵兰岛，在这项工作中。在现场测量数据的自动冰质分析仪每10米，从33米到2461米的深度。织物从一个轻微的各向异性织物在顶部，朝着一个强大的单一最大值在约2300米，这是典型的变形模式主要是由单轴压缩和简单的剪切驱动。在全新世到威斯康星州的气候转变中，观察到了组构加强的急剧增加。在格陵兰和南极洲的几个冰芯中观察到了类似的加强，朝向各向异性的单一最大型结构，这可以归因于气候转变时冰粘度变化与应力剪切分量影响之间的正反馈。在岩芯底部观察到厘米尺度的突变结构（组构和微观结构）。它们的位置与Dahl-Jensen及其合著者（2013年）用于气候重建的折叠假说非常一致。比较其他两个冰芯钻沿着同一脊; GRIP冰芯钻在冰盖的首脑会议，和NorthGRIP冰芯，钻325公里的NNW的首脑会议沿着脊，365公里的上游NEEM。组构剖面清楚地反映了当沿脊向西北沿着从GRIP向NorthGRIP和NEEM移动时剪切变形的增加。NEEM和NorthGRIP之间的组构剖面的差异也证明了与NorthGRIP处更尖锐的脊相关的更强的横向延伸。参考文献：Dahl-Jensen，D.共120位作者。Eemian interglacial reconstructed from a Greenland folded ice core，Nature，493，489-493，2013.
Fabric (distribution of crystallographic orientations) profile along the full NEEM ice core, Greenland, is presented in this work. Data were measured in the field by an Automatic Ice Texture Analyzer every 10 m, from 33 m down to 2461 m depth. The fabric evolves from a slightly anisotropic fabric at the top, toward a strong single maximum at about 2300 m, which is typical of a deformation pattern mostly driven by uniaxial compression and simple shearing. A sharp increase in the fabric strengthening is observed at the Holocene to Wisconsin climatic transition. A similar strengthening, toward an anisotropic single maximum-type fabric, has been observed in several ice cores from Greenland and Antarctica, and can be attributed to a positive feedback between changes in ice viscosity at the climatic transition, and the impact of a shear component of stress. Centimeter scale abrupt texture (fabric and microstructure) variations are observed in the bottom part of the core. Their positions are in good agreement with the folding hypothesis used for a climatic reconstruction by Dahl-Jensen and co authors (2013). Comparison is made to two others ice cores drilled along the same ridge; the GRIP ice core drilled at the summit of the ice sheet, and the NorthGRIP ice core, drilled 325 km to the NNW of the summit along the ridge, and 365 km upstream from NEEM. The fabric profile clearly reflects the increase in shear deformation when moving NW along the ridge from GRIP to NorthGRIP and NEEM. The difference in fabric profiles between NEEM and NorthGRIP also evidences a stronger lateral extension associated with a sharper ridge at NorthGRIP. References: Dahl-Jensen, D. and 120 co-authors. Eemian interglacial reconstructed from a Greenland folded ice core, Nature, 493, 489–493, 2013.