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

该奖项支持对极地冰孔中视频观测到的光学特征(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和较长周期信号。以前的项目中存在钻孔测井记录，在这个基于实验室的项目中，这些测井记录的解释将得到改进。这些特征的起源引起了冰芯社区的广泛兴趣。如果有些成分与沉积环境的季节性以外的变化有关，可能会看到重要的气候旋回。如果一些成分与沉积后再工作有关，将获得对改变雪和降雪的物理过程的洞察，以及对从古气候角度解释化学记录的影响。为了在未来的冰芯和气候变化研究中最大限度地利用这些特征，该项目的两个主要目标是确定是什么物理原因造成了我们所看到的光学差异，以及确定了导致这些物理差异的环境过程。在NICL的实验室中，通过沿着冰芯的部分运行钻孔摄像机，制作从冰芯反射的光的光学日志，将尽可能接近地重新创造井壁记录的条件。将识别与光学特征相关的物理变量的组合。辐射传输模型将用于帮助解释这些测量结果，并确定改进后的未来测井仪器的最佳配置。将尝试确定这些特征的原点。存在两种广泛的可能性：1)沉积环境的时间变化，2)沉积后的改造。这个项目代表着用钻孔光学方法研究古气候的新途径迈出了重要的一步。更广泛的影响包括加强研究和教育的基础设施，因为该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理来记录物理变量的快速方法。由于这种方法不需要岩心，因此它可以用于快速钻孔或岩心质量较差的地方。该项目将支持一名研究生，他将在首席调查员的指导下开展这一项目。通过与当地一所中学的科学和数学教师持续合作，K-12教育将得到加强。将通过与挪威极地研究所的同事就该项目开展工作来扩大国际合作，并将通过一个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.