Anisotropic Ice and Stratigraphic Disturbances

沃丁顿/1246045该奖项支持一项研究极地冰盖地层中褶皱和其他扰动的开始和发展的项目。这项工作的学术价值在于，它将有助于更好地理解控制冰层中这些地层特征发展的颗粒尺度过程，并有助于回答诸如哪些过程可以引发这种干扰等问题。雪沉积在极地冰盖上，通常是平坦的，厚度沿层变化缓慢。然而，冰芯和探冰雷达显示，在某些情况下，在转化为冰之后，经过长时间的埋藏，这些层可能会折叠，形成挤压膨胀结构(花束)，并被冰流剪切，规模从厘米到数百米不等。造成这些骚乱的过程仍然知之甚少。扰动似乎首先在冰晶尺度上发展，然后随着持续的冰流和应变而向上扩展到更大的尺度。造成厘米尺度层扭曲的晶体尺度过程将使用微结构建模程序包ELE来模拟，并受来自西南极冰盖分割冰芯的组构薄片和颗粒伸长测量的约束。本文将用全应力连续各向异性冰流模型和冰-组构演化模型相结合的方法来研究各向异性冰的整体流动，以了解流动扰动在米级和更大尺度上的演化和发展。这项研究的结果将有助于未来冰芯的选址，以及冰芯和雷达中的地层学解释，并将为冰盖流动模型提供更好的流变学和地层学描述。更广泛的影响是，它将使人们对造成地层扰动的冰动力学有更好的理解。这些信息对于限制古气候研究中冰芯的深度-年龄关系是有价值的。这将使研究人员能够将当前的气候变化置于更准确的背景下。该项目将为一名研究生提供三年的支持，并为一名本科生研究助理提供支持和研究经验；这将有助于培养解决未来冰川学和气候变化重要问题所需的人才。研究将通过外联活动向公众传播，研究结果将通过公共和专业会议以及期刊出版物传播。该项目不需要在南极洲进行实地工作。

Waddington/1246045 This award supports a project to investigate the onset and growth of folds and other disturbances seen in the stratigraphic layers of polar ice sheets. The intellectual merit of the work is that it will lead to a better understanding of the grain-scale processes that control the development of these stratigraphic features in the ice and will help answer questions such as what processes can initiate such disturbances. Snow is deposited on polar ice sheets in layers that are generally flat, with thicknesses that vary slowly along the layers. However, ice cores and ice-penetrating radar show that in some cases, after conversion to ice, and following lengthy burial, the layers can become folded, develop pinch-and-swell structures (boudinage), and be sheared by ice flow, at scales ranging from centimeters to hundreds of meters. The processes causing these disturbances are still poorly understood. Disturbances appear to develop first at the ice-crystal scale, then cascade up to larger scales with continuing ice flow and strain. Crystal-scale processes causing distortions of cm-scale layers will be modeled using Elle, a microstructure-modeling package, and constrained by fabric thin-sections and grain-elongation measurements from the West Antarctic Ice Sheet divide ice-core. A full-stress continuum anisotropic ice-flow model coupled to an ice-fabric evolution model will be used to study bulk flow of anisotropic ice, to understand evolution and growth of flow disturbances on the meter and larger scale. Results from this study will assist in future ice-core site selection, and interpretation of stratigraphy in ice cores and radar, and will provide improved descriptions of rheology and stratigraphy for ice-sheet flow models.The broader impacts are that it will bring greater understanding to ice dynamics responsible for stratigraphic disturbance. This information is valuable to constrain depth-age relationships in ice cores for paleoclimate study. This will allow researchers to put current climate change in a more accurate context. This project will provide three years of support for a graduate student as well as support and research experience for an undergraduate research assistant; this will contribute to development of talent needed to address important future questions in glaciology and climate change. The research will be communicated to the public through outreach events and results from the study will be disseminated through public and professional meetings as well as journal publications. The project does not require field work in Antarctica.