Collaborative Research: Computational Methods Supporting Joint Seismic and Radar Inversion for Ice Fabric and Temperature in Streaming Flow

合作研究：支持地震和雷达联合反演冰网和流动温度的计算方法

• 批准号: 1643301
• 负责人: Christopher Gerbi
• 金额: $ 19.5万
• 依托单位: University of Maine
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1643301&HistoricalAwards=false
• 关键词: Collaborative; Research; Computational; Methods; Supporting

Gerbi/1643301This award supports a project to develop software that will allow researchers considering seismic or radar field surveys to test, ahead of time, whether the data they plan to collect will have sufficient resolution to measure the natural variations in the mechanical properties of ice, which determine the response of flowing ice to changing climatic conditions. The mechanical properties of ice depend largely on the temperature and the orientation of the crystals that make up the ice. The most accurate method for measuring ice crystal orientation and temperature is through drilling and direct analysis of an ice core. However, this method is very costly, time-consuming, and limited in spatial coverage. Geophysical techniques, such as seismic and radar, can cover much more area, but we have little knowledge about the practical limitations of these techniques as they relate to calculating mechanical properties. This project addresses that knowledge gap through construction of a computational toolbox that will allow accurate assessment of the ability of geophysical surveys to image crystal orientation and ice temperature. Researchers can then use these tools to adjust the field survey plans to maximize the return on investment. By working to improve the efficiency and effectiveness of future geophysical work related to glacial flow, this proposal will improve scientists? ability to quantify sea-level variations within the larger context of climate change. The project includes building new user-friendly, publicly accessible software and instructional modules. The work will provide training for graduate and undergraduate students, who will play a role in research and develop instructional materials. Ice viscosity, the resistance of ice to flow, exerts significant control over ice velocity. Therefore, mapping ice viscosity is important for understanding the current and future behavior of glaciers and ice sheets. To do so, scientists must determine the temperature and crystal orientation fabric throughout the ice. Seismic and radar techniques can survey large areas quickly, and thus are promising, yet not fully tested, methods to efficiently measure the thermal and mechanical structure of flowing ice. As part of this project, scientists will develop and use a computational framework to quantify the degree to which seismic and radar techniques can resolve the crystal orientation fabric and temperature of streaming ice, and then test how sensitive ice flow is to the attendant uncertainty. To meet these goals, a numerical toolbox will be built which will allow the glacier/ice stream geometry and physical properties (temperature, crystal orientation fabric, density and acidity) to be varied. The toolbox will be capable of both creating synthetic radar and seismic profiles through forward modeling and inverting synthetic profiles to allow evaluation of how well geophysical techniques can image the original thermal and mechanical structure. These simulated radar and seismic data will allow scientists to better quantify the influence of the variability in mechanical properties of the ice on flow velocities and patterns. The results of this work will guide planning for future field campaigns, making them more effective and efficient. This project does not require fieldwork in the Antarctic.

Gerbi/1643301该奖项支持一个开发软件的项目，该软件将允许考虑地震或雷达现场调查的研究人员提前测试他们计划收集的数据是否具有足够的分辨率来测量冰的机械特性的自然变化，这决定了流动冰对气候条件变化的反应。冰的机械性质很大程度上取决于温度和组成冰的晶体的方向。 测量冰晶方向和温度的最准确方法是通过钻孔和直接分析冰芯。 然而，这种方法是非常昂贵的，耗时的，并在空间覆盖范围有限。 地球物理技术，如地震和雷达，可以覆盖更大的区域，但我们对这些技术的实际局限性知之甚少，因为它们与计算力学性能有关。 该项目通过建立一个计算工具箱来填补这一知识空白，该工具箱将能够准确评估地球物理调查对晶体取向和冰温成像的能力。 然后，研究人员可以使用这些工具来调整实地调查计划，以最大限度地提高投资回报。 通过努力提高未来与冰川流动有关的地球物理工作的效率和有效性，这项建议将提高科学家？在气候变化的大背景下量化海平面变化的能力。 该项目包括建立新的用户友好，公开访问的软件和教学模块。 这项工作将为研究生和本科生提供培训，他们将在研究和开发教学材料方面发挥作用。冰的粘度，即冰对流动的阻力，对冰的速度有重要的控制作用。 因此，绘制冰的粘性对于了解冰川和冰盖的当前和未来行为非常重要。 要做到这一点，科学家必须确定整个冰的温度和晶体取向结构。地震和雷达技术可以快速地调查大面积区域，因此是有前途的，但尚未完全测试，有效地测量流动冰的热和机械结构的方法。 作为该项目的一部分，科学家们将开发和使用一个计算框架来量化地震和雷达技术可以解决流动冰的晶体取向结构和温度的程度，然后测试冰流对随之而来的不确定性的敏感程度。 为了实现这些目标，将建立一个数值工具箱，使冰川/冰流的几何形状和物理特性（温度、晶体取向结构、密度和酸度）能够变化。该工具箱将能够通过正演建模和反演合成剖面创建合成雷达和地震剖面，以评估地球物理技术如何能够很好地对原始热结构和机械结构进行成像。这些模拟的雷达和地震数据将使科学家能够更好地量化冰的机械特性的变化对流速和模式的影响。 这项工作的结果将指导今后外地运动的规划，使其更加有效和高效。该项目不需要在南极进行实地考察。