Collaborative Research: Observations and Modeling of Flow and Fracture Processes Leading to Iceberg Calving

世界上大部分冰川的冰都是通过冰山的崩解而消失的。 了解这一过程对于预测海平面上升、重建过去大冰盖的变化以及分析许多北极冰川现在和未来的变化至关重要。 不幸的是，这个过程是复杂的，没有令人满意的产犊关系，可以纳入数值模型已经开发和验证。 一个独特的机会，这样做，现在就在手边：一个广泛的数据集的几何形状，流动和崩解的迅速瓦解的哥伦比亚冰川，阿拉斯加，已经开发了由美国地质调查局，断裂力学的新发展，现在有可能计算裂缝的相互作用和其他过程的断裂问题是至关重要的。 研究人员将主要使用航空摄影测量法在该冰川的终点及其附近收集额外的高度详细的应变和几何数据。 然后，他们将在新开发的裂缝和流动模型中使用这些和现有的数据集。 这些模型采用离散位移分析（DDA）以及有限元模型，将用于模拟断裂并确定产犊和水流之间的相互作用。 将对结果进行测试，看看冰川目前的行为是否可以很好地模拟，如果可以，看看1978-95年冰川变化的历史是否可以准确地模拟。 然后将探讨其他应用程序的建模的通用性。 预计这项研究将产生1）一个详细的观测数据集的动力学和冰解供他人使用，2）进一步了解冰山放电机制和冰解和冰动力学之间的相互关系，3）更好地了解大规模断裂过程的冰，4）新的冰川学建模工具，如DDA，（5）冰山崩解关系，它将有助于广泛的古冰川学和现代冰盖和冰川研究，以及冰山泄流在冰/海相互作用中的作用的研究。

Most of the ice lost from the world's glaciers is lost through the calving of icebergs. An understanding of this process is vital to projections of sea-level rise, to reconstructing changes in the great ice sheets of the past, and to analyses of present and future changes in many Arctic glaciers. Unfortunately, the process is complex and no satisfactory calving relation that can be incorporated into numerical models has been developed and validated. A unique opportunity to do this is now at hand: An extensive data set on geometry, flow and calving of the rapidly disintegrating Columbia Glacier, Alaska, has been developed by the U.S. Geological Survey, and new developments in fracture mechanics now make it possible to compute crevasse interactions and other processes that are critical to the breakoff problem. The investigators will collect additional, highly-detailed strain and geometric data at and near the terminus of this glacier using primarily aerial photogrammetry. They will then use these and the existing data set in newly-developed fracture and flow models. These models, which use discrete displacement analysis (DDA) as well as finite element models, will be used to simulate breakoffs and define the interaction between calving and flow. The results will be tested to see if the current behavior of the glacier can be simulated well, and if so, to see if the 1978-95 history of change in this glacier can be modeled accurately. Then the generality of the modeling for other applications will be explored. It is expected that this study will produce 1) a detailed observational data set on dynamics and calving for use by others, 2) further insight into iceberg discharge mechanisms and the interrelations between calving and ice dynamics, 3) better knowledge of large-scale fracture processes in ice, 4) new glaciological modeling tools, such as DDA, and 5) an iceberg calving relation which will be useful for a wide range of paleoglaciological and current ice sheet and glacier inves tigations as well as studies of the role of iceberg discharges in ice/ocean interactions.