Collaborative Research: Investigating jamming in iceberg-choked fjords with field observations, laboratory experiments, and numerical models

非技术：该奖项由MPS的凝聚态物理项目、多学科事务办公室和GEO的北极自然科学项目共同资助。地球的极地地区是许多动态物理过程的家园。虽然“冰川”这个词可能会让人联想到坚忍而缓慢移动的冰川，它们的变化肉眼无法分辨，但情况并非总是如此。冰川活动最活跃的地区之一是格陵兰岛巨大的沿海峡湾。宽5-10公里、深达1公里的冰河正迅速流向海洋。在这些冰川的末端，冰与海的交汇处，冰山不断地断裂或“分裂”到海洋中。排放到海洋中的冰大约有30-50%是通过冰裂产生的，而不是通过融化等其他机制。不幸的是，控制产犊的物理过程还没有被很好地理解。一个可能的影响是存在一个冰凌，这是一个漂浮的冰山和海冰层，从冰川前端延伸数公里。msamange本质上是一种大规模的准二维颗粒材料，它可能对冰山崩解率和我们探测冰山崩解的能力产生重大影响。这个合作项目的目的是确定正确的物理描述冰的直径力学，以及它对冰山崩解的影响。这是通过卫星图像、小规模实验室实验和理论建模的跨学科结合来完成的。通过汇集凝聚态物理学的思想来研究大规模的冰期过程，该项目揭示了塑造我们星球极地地区的潜在机制。技术：这个项目的主要目标是表征冰的流变学，冰是一种紧密堆积的颗粒状材料，由冰山和海冰组成，在格陵兰岛的峡湾中发现。在颗粒状材料中，冰的直径是独一无二的，因为它包含了非常大的碎屑（在各个方向上都有10到100米的尺度），它被限制在准二维环境中流动，并且漂浮在自己的融化物中。冰凌运动和范围的季节变化与冰山崩解速率的季节变化具有良好的相关性，表明冰凌是出口冰川和冰盖稳定性的重要控制因素。冰凌的动力学、能量学和海洋学后果基本上还没有被研究过。研究小组的目标是通过结合实地观察分析、实验室实验和数值模拟来研究冰的直径。卫星图像，连同先前收集的延时摄影和地面雷达数据，被分析以产生冰的速度场和量化冰山大小的分布。这项工作提供了新的见解冰的运动和组成，并作为实验室和数值模拟实验的基准。此外，还进行了用模型终端推动水箱中的合成冰山的实验。这些实验研究了在崩解期间和崩解之间模拟冰山的粒子的干扰，以研究应力通过冰凌的传播。最后，进行了数值模拟实验，利用离散颗粒和连续体模型模拟了冰的直径。模型流变学可以调整，以找到与现场观测和实验室实验相一致的冰的描述。

Non-Technical:This award is jointly funded by the Condensed Matter Physics Program and the Office of Multidisciplinary Affairs in MPS and the Artic Natural Sciences Program in GEO. The polar regions of our planet are home to many dynamic physical processes. Although the word "glacier" may invoke connotations of stoic and slow-moving mountains of ice whose changes are indistinguishable to the eye, this is not always the case. Among the most active regions of glaciological activity are the massive coastal fjords in Greenland. Rivers of ice which are 5-10 km wide and up to 1 km deep are rapidly flowing towards the ocean. At the end of these glaciers, where the ice meets the sea, icebergs are constantly breaking off or "calving" into the ocean. Approximately 30-50% of all ice discharged into the ocean occurs through calving, as opposed to other mechanisms such as melting. Unfortunately, the physical processes which control calving are not well understood. One possible influence is the presence of an ice mélange, which is a floating layer of icebergs and sea ice extending many kilometers away from the front of the glacier. The mélange is essentially a large-scale, quasi-two dimensional granular material, which can potentially have a large impact on calving rates and our ability to detect iceberg calving. This collaborative project aims to determine the correct physical description of ice mélange mechanics, as well as its influences on iceberg calving. This is accomplished through an interdisciplinary combination of satellite imagery, small-scale laboratory experiments, and theoretical modeling. By bringing together ideas in condensed matter physics to study large-scale glaciological processes, the project sheds new light on the underlying mechanisms which shape the polar regions of our planet. Technical:The primary goal of this project is to characterize the rheology of ice mélange, a closely-packed granular material composed of icebergs and sea ice that is found in fjords throughout Greenland. Ice mélange is unique among granular materials in that it contains exceptionally large clasts (10's to 100's of meters in scale in all directions), is constrained to flow in a quasi-two-dimensional setting, and floats in its own melt. Seasonal variations in ice mélange motion and extent are well-correlated with seasonal variations in iceberg calving rates, suggesting that ice mélange is an important control on outlet glacier and ice sheet stability. The dynamics, energetics, and oceanographic consequences of ice mélange are essentially unexplored. The research team's aim is to study ice mélange by combining analysis of field observations with laboratory experiments and numerical modeling. Satellite imagery, along with previously collected time lapse photography and terrestrial radar data, is analyzed to produce ice mélange velocity fields and quantify iceberg-size distributions. This work provides new insights into ice mélange kinematics and composition, and serves as a benchmark for laboratory and numerical modeling experiments. In addition, experiments are conducted in which synthetic icebergs in a water tank are pushed by a model terminus. These experiments study jamming of particles that model icebergs during and between calving events to investigate stress transmission through ice mélange. Finally, numerical experiments are performed in which ice mélange is simulated using discrete particle and continuum models adapted from previous work on granular materials. The model rheology can be adjusted to find a description of ice mélange that is consistent with field observations and laboratory experiments.