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: 1643353
• 负责人: Knut Christianson
• 金额: $ 13.36万
• 依托单位: University of Washington
• 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 2020-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1643353&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，该项目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机械特性的自然变化，这决定了流冰对气候条件变化的响应。冰的机械特性很大程度上取决于组成冰的晶体的温度和方向。 测量冰晶方向和温度的最准确方法是通过钻探和直接分析冰芯。 然而，这种方法成本高昂、耗时且空间覆盖范围有限。 地震和雷达等地球物理技术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，因为它们与计算机械特性有关。 该项目通过构建计算工具箱来解决这一知识差距，该工具箱将允许准确评估地球物理勘测对晶体取向和冰温进行成像的能力。 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。 通过致力于提高未来与冰川流相关的地球物理工作的效率和效果，该提案将提高科学家的工作效率和有效性。在气候变化的大背景下量化海平面变化的能力。 该项目包括构建新的用户友好型、可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，即冰的流动阻力，对冰的速度具有重要的控制作用。 因此，绘制冰粘度图对于了解冰川和冰盖当前和未来的行为非常重要。 为此，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勘测大面积区域，因此是有效测量流冰热结构和机械结构的有前景但尚未经过充分测试的方法。 作为该项目的一部分，科学家将开发并使用计算框架来量化地震和雷达技术可以解析流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，该工具箱将允许改变冰川/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）。该工具箱将能够通过正演建模和反演合成剖面来创建合成雷达和地震剖面，以评估地球物理技术对原始热结构和机械结构成像的效果。这些模拟雷达和地震数据将使科学家能够更好地量化冰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未来实地活动的规划，使其更加有效和高效。该项目不需要在南极进行实地考察。

项目成果

ImpDAR: an open-source impulse radar processor

• DOI: 10.1017/aog.2020.44
• 发表时间: 2020-04
• 期刊: Annals of Glaciology
• 影响因子: 2.9
• 作者: D. Lilien;B. Hills;Joshua Driscol;R. Jacobel;K. Christianson

Thermal Weakening, Convergent Flow, and Vertical Heat Transport in the Northeast Greenland Ice Stream Shear Margins

• DOI: 10.1029/2019gl083436
• 发表时间: 2019-07-28
• 期刊: GEOPHYSICAL RESEARCH LETTERS
• 影响因子: 5.2
• 作者: Holschuh, N.;Lilien, D. A.;Christianson, K.
• 通讯作者: Christianson, K.

Geophysics and Thermodynamics at South Pole Lake Indicate Stability and a Regionally Thawed Bed

南极湖的地球物理学和热力学表明稳定性和区域性解冻床

• DOI: 10.1029/2021gl096218
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Hills, Benjamin H.;Christianson, Knut;Hoffman, Andrew O.;Fudge, T. J.;Holschuh, Nicholas;Kahle, Emma C.;Conway, Howard;Christian, John E.;Horlings, Annika N.;O’Connor, Gemma K.
• 通讯作者: O’Connor, Gemma K.

A framework for attenuation method selection evaluated with ice-penetrating radar data at South Pole Lake

• DOI: 10.1017/aog.2020.32
• 发表时间: 2020-04
• 期刊: Annals of Glaciology
• 影响因子: 2.9
• 作者: B. Hills;K. Christianson;N. Holschuh