Collaborative Research: Flow and Fracture Dynamics in an Ice Shelf Lateral Margin: Observations and Modeling of the McMurdo Shear Zone

该合同支持对McMurdo剪切带（SZ）进行综合现场观测、遥感和数值模拟研究。SZ是一条5-10公里宽的严重裂缝冰带，将麦克默多冰架和罗斯冰架分开，是罗斯冰架横向支撑的重要区域。以往的雷达和遥感研究揭示了一幅神秘的SZ图像，在深度探测到的裂缝没有明显的表面表达，并且其方向可能与观测到的流场不一致。在提出的工作中，我们试图验证这样的假设，即SZ是一个混沌拉格朗日混合区，与（相交的）埋藏裂缝混合，导致流变不稳定，可能允许大规模的速度不连续。这项工作将包括利用探地雷达对裂缝分布和结构进行详细的实地观测，并利用GPS和遥感对SZ的流场和应力场进行观测。由于SZ的危险性质，雷达调查将主要在轻型机器人车辆的帮助下进行。观测结果将用于开发冰架剪切边缘行为的有限元模型。这个项目的知识价值是增加了对冰架剪切边缘动力学的理解。剪切边缘对冰架的稳定性起着关键作用，而冰架反过来又调节从冰盖穿过接地线进入海洋的冰通量。从这个项目中获得的见解将改进正在开发的大型模型，以预测冰盖的演变和未来海平面上升的速度，这是一个巨大的社会关注的话题。该项目更广泛的影响包括改善美国南极计划后勤规划的基础，以及吸引K-12学生参与科学发现的众多机会。罗斯冰架和麦克默多冰架之间的剪切带裂缝加剧，将使重型穿越车辆无法穿越地表，这将导致向南极运送燃料的成本增加，并导致在南极大陆执行科学任务的重型运输飞机的飞行时间减少。我们的多学科研究结合了冰川学、数值模拟和机器人工程，以一种引人入胜的方式展示了机器人如何帮助科学家收集危险领域的测量数据。我们的推广活动将利用达特茅斯目前的NSF GK-12项目，建立在缅因大学最近的GK-12项目中建立的教师-教育者关系，并将项目结果纳入缅因大学的IDEAS计划，该计划将计算建模与现有的中学科学课程相结合。这个奖项在南极洲进行实地考察。

Hamilton/1246400This award supports an integrated field observation, remote sensing and numerical modeling study of the McMurdo Shear Zone (SZ). The SZ is a 5-10 km wide strip of heavily crevassed ice that separates the McMurdo and Ross ice shelves, and is an important region of lateral support for the Ross Ice Shelf. Previous radar and remote sensing studies reveal an enigmatic picture of the SZ in which crevasses detected at depth have no apparent surface expression, and have orientations which are possibly inconsistent with the observed flow field. In the proposed work, we seek to test the hypothesis that the SZ is a zone of chaotic Lagrangian mixing with (intersecting) buried crevasses which leads to rheological instability, potentially allowing large scale velocity discontinuities. The work will involve detailed field-based observations of crevasse distributions and structure using ground-penetrating radar, and GPS and remote sensing observations of the flow and stress field in the SZ. Because of the hazardous nature of the SZ, the radar surveys will be conducted largely with the aid of a lightweight robotic vehicle. Observations will be used to develop a finite element model of ice shelf shear margin behavior. The intellectual merit of this project is an increased understanding of ice shelf shear margin dynamics. Shear margins play a key role in ice shelf stability, and ice shelves in turn modulate the flux of ice from the ice sheet across the grounding line to the ocean. Insights from this project will improve large-scale models being developed to predict ice sheet evolution and future rates of sea level rise, which are topics of enormous societal concern. The broader impacts of the project include an improved basis for US Antarctic Program logistics planning as well as numerous opportunities to engage K-12 students in scientific discovery. Intensified crevassing in the shear zone between the Ross and McMurdo ice shelves would preclude surface crossing by heavy traverse vehicles which would lead to increased costs of delivering fuel to South Pole and a concomitant loss of flight time provided by heavy-lift aircraft for science missions on the continent. Our multidisciplinary research combining glaciology, numerical modeling, and robotics engineering is an engaging way to show how robotics can assist scientists in collecting hazardous field measurements. Our outreach activities will leverage Dartmouth's current NSF GK-12 program, build on faculty-educator relationships established during University of Maine's recent GK-12 program, and incorporate project results into University of Maine's IDEAS initiative, which integrates computational modeling with the existing science curriculum at the middle school level. This award has field work in Antarctica.