Laboratory Study of Ice Deformation under Tidal Loading Conditions with Application to Antarctic Glaciers

1245871/麦卡锡该奖项支持一个项目，该项目使用一种新的、定制的低温摩擦装置进行实验室实验，以探索自然界中潮水冰川所经历的冰变形振荡应力。实验设计将探索周期性载荷下冰在岩石上滑动的动摩擦特性。尽管过去已经对冰的摩擦强度进行了研究，但这些研究都集中在恒定的加载和滑动速度上。这项工作的结果将改善对关键材料和摩擦特性的约束，并允许基于物理的预测因潮汐引起的应力变化而导致的冰川应变的幅度和相位，从而促进对冰流动力学的理解。这项工作的学术价值在于，它将导致对动态流变参数的更好理解，并将为动态冰川流动提供更好的预测工具。拟议的实验将提供南极冰川经历的真实频率的冰和岩石变形的动态材料特性。PI将测量从弹性到滞弹性再到粘性的材料响应的全光谱。这项研究将为提高冰川和冰流对外部强迫的响应的预测能力提供更好的约束条件。这项工作的更广泛影响包括提供可用于扩大我们对冰川流动的理解的材料特性估计，这些估计最终将用于海平面上升和冰盖稳定性的模型。预测近期海平面的能力取决于对南极冰流和冰川流动过程的了解。海洋潮汐对冰川流动的调节代表了一项自然实验，可以用来改善对冰和河床特性的了解，以及这些特性依赖于时间变化的作用力的方式。目前，潮汐强迫对冰川运动的影响还知之甚少，对潮汐载荷条件下冰的特性的了解也很有限。这项研究将通过研究地震学、冰川学和普通材料科学感兴趣的现象，产生超越极地科学的有趣结果。该项目将为两名本科生实习生提供宝贵的研究和实验室经验，并将为PI(目前是博士后)领导科学项目提供经验。这三位PI都是早期的职业科学家。这项提议不需要在南极进行实地考察。

1245871/McCarthyThis award supports a project to conduct laboratory experiments with a new, custom-fabricated cryo-friction apparatus to explore ice deformation oscillatory stresses like those experienced by tidewater glaciers in nature. The experimental design will explore the dynamic frictional properties of periodically loaded ice sliding on rock. Although the frictional strength of ice has been studied in the past these studies have all focused on constant rates of loading and sliding. The results of this work will advance understanding of ice stream dynamics by improving constraints on key material and frictional properties and allowing physics-based predictions of the amplitude and phase of glacier strain due to tidally induced stress variations. The intellectual merit of this work is that it will result in a better understanding of dynamic rheological parameters and will provide better predictive tools for dynamic glacier flow. The proposed experiments will provide dynamic material properties of ice and rock deformation at realistic frequencies experienced by Antarctic glaciers. The PIs will measure the full spectrum of material response from elastic to anelastic to viscous. The study will provide better constraints to improve predictive capability for glacier and ice-stream response to external forcing. The broader impacts of the work include providing estimates of material properties that can be used to broaden our understanding of glacier flow and that will ultimately be used for models of sea level rise and ice sheet stability. The ability to predict sea level in the near future is contingent on understanding of the processes responsible for flow of Antarctic ice streams and glaciers. Modulation of glacier flow by ocean tides represents a natural experiment that can be used to improve knowledge of ice and bed properties, and of the way in which these properties depend on time-varying forcings. Presently, the influence of tidal forcing on glacier movement is poorly understood, and knowledge of ice properties under tidal loading conditions is limited. The study will generate results of interest beyond polar science by examining phenomena that are of interest to seismology, glaciology and general materials science. The project will provide valuable research and laboratory experience for two undergraduate interns and will provide experience for the PI (currently a postdoc) in leading a scientific project. The three PIs are early career scientists. This proposal does not require fieldwork in the Antarctic.