A new generation of physically-based models for predicting ice-sheet fracture and sea level rise

海平面上升是全球变暖下世界面临的最关键问题之一。根据政府间气候变化专门委员会(IPCC)的数据，世界上10%的人口生活在易受洪水影响的低洼沿海地区。虽然20世纪海平面的上升主要是海水的热膨胀，但冰川和冰盖的质量损失现在是最大的贡献者。因此，有必要更新政府间气候变化专门委员会的海平面上升预测，目前认为这一预测处于可能结果的低端。然而，提供冰块质量损失的定量预测并不是一项容易的任务。冰山破裂和剥离(崩解)是一种复杂的现象，发生在很长的时间尺度上，受机械、热和水力破裂过程的支配。这个博士项目的目标是开发新一代预测冰山崩解和相关海平面上升的模型。这将通过第一次包括融水驱动的裂缝的物理学来实现；这将是一个科学里程碑，将通过将新的数学相场范式引入该学科而成为可能。目前的经验估计无法捕捉到关键的物理特征，如冰的粘性行为、热效应或融水在驱动水力裂缝方面的作用。这个博士项目将通过开发一个多物理的有限元框架来整合融水驱动的裂缝的物理学。这项工作的主要内容包括相场断裂模型、热粘弹性和孔弹性的结合。模型预测将以卫星和雷达数据为基准。这个博士项目将提供新一代冰盖破裂模型，可以模拟潜在的物理机制。这将第一次带来对冰山崩解的定量洞察；由于冰川带来的挑战和回报，冰山崩解被称为冰川学中的“圣杯”问题。计算机代码将免费提供，为科学界提供工具，以减少气候变化影响预测的不确定性。与格兰瑟姆研究所的联系将被用来将科学发现转化为政策，最大限度地发挥这篇博士论文的社会影响。

Sea-level rise is one of the most critical issues the world faces under global warming. According to the Intergovernmental Panel on Climate Change (IPCC), 10% of the world's population live in low-lying coastal regions that are susceptible to flooding. While twentieth-century sea-level rise was dominated by thermal expansion of ocean water, mass loss from glaciers and ice sheets is now the largest contributor. As a consequence, there is a need for updating IPCC sea-level rise projections, which are now thought to be on the low end of possible outcomes. However, delivering quantitative predictions of ice mass loss is not an easy task. Iceberg fracture and detachment (calving) is a complex phenomenon that occurs over long time scales and is governed by mechanical, thermal and hydraulic fracture processes. The objective of this PhD project is to develop a new generation of models for predicting iceberg calving and the associated sea-level rise. This will be achieved by including - for the first time - the physics of meltwater-driven fracture; a scientific milestone that will be made possible by bringing a new mathematical phase field paradigm to the discipline. Current empirical estimates cannot capture key physical features, such as the viscous behaviour of ice, thermal effects or the role of meltwater in driving hydraulic fractures. This PhD project will incorporate the physics of meltwater-driven fracture by developing a multi-physics finite element framework. Key elements of the work involve the combination of phase field fracture modelling, thermo-viscoelasticity and poroelasticity. Model predictions will be benchmarked against satellite and radar data.This PhD project will deliver a new generation of ice-sheet fracture models that can simulate the underlying physical mechanisms. This will bring, for the first time, quantitative insight into iceberg calving; a phenomenon referred to as the "holy grail" problem in glaciology, due to the challenges and rewards that it presents. Computer codes will be made freely available, providing the scientific community with tools to reduce uncertainty in the prediction of climate change effects. The connection with the Grantham Institute will be exploited to translate scientific findings into policy, maximising the societal impact of this PhD thesis.