Borehole Optical Stratigraphy: Ice Microphysics, Climate Change, and the Optical Properties of Firn

该奖项支持通过视频在极地冰层钻孔中观察到的光学特征（亮区和暗区）的物理性质和环境起源的研究。 这些特征似乎包括年度信号以及较长周期的信号。 钻孔记录存在于以前的项目中，在这个基于实验室的项目中，这些记录的解释将得到改进。 这些特征的起源对冰芯社区有着广泛的兴趣。 如果某些成分与季节性以外的沉积环境变化有关，则可能会看到重要的气候循环。 如果某些成分与沉积后的改造有关，则将深入了解改变雪和积雪的物理过程，以及解释古气候方面的化学记录的含义。 为了在未来的冰芯和气候变化研究中充分利用这些特征，该项目的两个主要目标是确定物理上导致我们看到的光学差异的原因，并确定引起这些物理差异的环境过程。 在NICL的实验室中，将通过使钻孔摄像机沿着冰芯部分运行，尽可能接近地再现钻孔壁的测井条件，从而制作从冰芯反射的光的光学测井。 将确定与光学特征相关的物理变量的组合。 辐射传输模型将被用来帮助解释这些测量，并确定一个改进的未来测井工具的最佳配置。 将尝试确定这些特征的来源。 存在两种广泛的可能性：1）沉积环境的时间变化，和2）沉积后的改造。 这一项目代表了利用钻孔光学方法研究古气候的新方法的重要一步。 更广泛的影响包括加强研究和教育的基础设施，因为这一仪器将补充高分辨率连续熔化化学技术，并提供一种利用光学特征作为气候信号代用指标记录物理变量的快速方法。 由于这种方法不需要岩心，因此可以用于快速钻取的通道孔或岩心质量较差的地方。 该项目将支持一名研究生，他将在主要研究者的指导下开展该项目。 K-12教育将通过与当地一所中学的科学和数学教师的持续合作得到加强。 将通过与挪威极地研究所的同事就该项目开展工作，扩大国际合作，并将通过面向公众的项目网站广泛传播成果。

This award supports a study of the physical nature and environmental origin of optical features (light and dark zones) observed by video in boreholes in polar ice. These features appear to include an annual signal, as well as longer period signals. Borehole logs exist from a previous project, and in this lab-based project the interpretation of these logs will be improved. The origin of the features is of broad interest to the ice-core community. If some components relate to changes in the depositional environment beyond seasonality, important climatic cycles may be seen. If some components relate to post-depositional reworking, insights will be gained into the physical processes that change snow and firn, and the implications for interpretation of the chemical record in terms of paleoclimate. In order to exploit these features to best advantage in future ice-core and climate-change research, the two principal objectives of this project are to determine what physically causes the optical differences that we see and to determine the environmental processes that give rise to these physical differences. In the laboratory at NICL the conditions of a log of a borehole wall will be re-created as closely as possible by running the borehole video camera along sections of ice core, making an optical log of light reflected from the core. Combinations of physical variables that are correlated with optical features will be identified. A radiative-transfer model will be used to aid in the interpretation of these measurements, and to determine the optimum configuration for an improved future logging tool. An attempt will be made to determine the origin of the features. Two broad possibilities exist: 1) temporal changes in the depositional environment, and 2) post-depositional reworking. This project represents an important step toward a new way of learning about paleoclimate with borehole optical methods. Broader impacts include enhancing the infrastructure for research and education, since this instrument will complement high-resolution continuous-melter chemistry techniques and provide a rapid way to log physical variables using optical features as a proxy for climate signals. Since no core is required for this method, it can be used in rapidly drilled access holes or where core quality is poor. This project will support a graduate student who will carry out this project under the direction of the Principal Investigator. K-12 education will be enhanced through an ongoing collaboration with a science and math teacher from a local middle school. International collaboration will be expanded through work on this project with colleagues at the Norwegian Polar Institute and broad dissemination of results will occur through a project website for the general public.