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

合作研究：通过现场观察、实验室实验和数值模型研究冰山堵塞的峡湾中的干扰

• 批准号: 1506307
• 负责人: Jason Amundson
• 金额: $ 9.68万
• 依托单位: University of Alaska Southeast Juneau Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506307&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; jamming; iceberg

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.

非技术：该奖项由凝聚态物理项目和MPS多学科事务办公室以及地球物理组织的北极自然科学项目共同资助。我们星球的极地是许多动态物理过程的发源地。尽管“冰川”这个词可能会让人联想到坚忍和缓慢移动的冰山，它们的变化用肉眼看不出来，但情况并不总是如此。格陵兰的大型沿海峡湾是冰川学活动最活跃的地区之一。宽5-10公里、深达1公里的冰河正迅速流向海洋。在这些冰川的尽头，也就是冰与海的交汇处，冰山不断地破裂或“崩解”进入海洋。排入海洋的冰中约有30%-50%是通过崩解发生的，而不是通过其他机制，如融化。不幸的是，控制产卵的物理过程还没有被很好地理解。一种可能的影响是冰川混杂的存在，这是一层漂浮的冰山和海冰，从冰川前面延伸了许多公里。混合体本质上是一种大规模的准二维颗粒状物质，它可能会对冰解率和我们探测冰山崩解的能力产生很大影响。这个合作项目的目的是确定对冰川混杂力学的正确物理描述，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模型的跨学科组合来实现的。通过将凝聚态物理中的想法结合起来研究大规模冰川过程，该项目为我们揭示了塑造地球极地地区的潜在机制。技术：该项目的主要目标是描述冰混杂的流变性，这是一种紧密堆积的颗粒状物质，由冰山和海冰组成，在整个格陵兰的峡湾中都能找到。冰混杂岩在颗粒状物质中是独一无二的，因为它包含非常大的碎屑(10‘S到100’S，全方位)，被限制在准二维环境中流动，并漂浮在自己的熔体中。冰川运动和冰盖范围的季节变化与冰山崩解速率的季节变化有很好的相关性，表明冰川混杂是出口冰川和冰盖稳定性的重要控制因素。冰川混杂的动力学、能量学和海洋学后果基本上是未知的。研究小组的目标是通过野外观测分析、实验室实验和数值模拟相结合的方式来研究冰川混杂。分析卫星图像以及之前收集的时延摄影和地面雷达数据，以产生冰混和速度场并量化冰山大小分布。这项工作为冰混杂运动学和组成提供了新的见解，并作为实验室和数值模拟实验的基准。此外，还进行了水箱中的合成冰山在模型终端的推动下的实验。这些实验研究了冰山模型粒子在冰解过程中和之间的堵塞，以研究冰川中的应力传递。最后，进行了数值实验，其中冰混杂使用离散粒子模型和连续介质模型进行了模拟，这些模型来自于以前关于颗粒材料的工作。可以调整模型的流变学，以找到与野外观测和实验室实验相一致的冰混杂描述。