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Laser Ultrasound Observations of Mechanical Property Variations in Ice Cores

机译：冰芯力学性能变化的激光超声观察

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The study of climate records in ice cores requires an accurate determination of annual layering within the cores in order to establish a depth-age relationship. Existing tools to delineate these annual layers are based on observations of changes in optical, chemical, and electromagnetic properties. In practice, no single technique captures every layer in all circumstances. Therefore, the best estimates of annual layering are produced by analyzing a combination of measurable ice properties. We present a novel and complimentary elastic wave remote sensing method based on laser ultrasonics. This method is used to measure variations in ultrasonic wave arrival times and velocity along the core with millimeter resolution. The laser ultrasound system does not require contact with the ice core and is non-destructive. Custom optical windows allow the source and receiver lasers to be located outside the cold room, while the core is scanned by moving it with a computer-controlled stage. We present results from Antarctic firn and ice cores that lack visual evidence of a layered structure, but do show travel-time and velocity variations. In the future, these new data may be used to infer stratigraphic layers from elastic parameter variations within an ice core, as well as analyze ice crystal fabrics.
机译：对冰芯气候记录的研究需要准确确定冰芯内的年度分层，以便建立深度-年龄关系。用来描述这些年度层的现有工具是基于对光学，化学和电磁特性变化的观察。在实践中，没有任何一种技术可以在所有情况下捕获每个层。因此，通过分析可测量的冰属性的组合，可以得出年度分层的最佳估计。我们提出了一种基于激光超声的新颖且互补的弹性波遥感方法。该方法用于以毫米分辨率测量超声波到达时间和沿铁心的速度变化。激光超声系统不需要与冰芯接触，并且是非破坏性的。定制的光学窗口允许将源激光器和接收器激光器放置在冷藏室之外，同时使用计算机控制的工作台移动纤芯来扫描纤芯。我们提出的南极火星和冰芯的结果缺乏层状结构的视觉证据，但确实显示了传播时间和速度变化。将来，这些新数据可能会用于从冰芯内的弹性参数变化推断地层，以及分析冰晶织物。

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