NSF-NERC: Disintegration of Marine Ice-sheets using Novel Optimised Simulations (DOMINOS)

该项目为美国国家科学基金会(NSF)和英国自然环境研究理事会(NERC)发起的联合倡议做出了贡献，该倡议旨在大幅改善对南极洲西部斯韦茨冰川造成的冰流失和海平面上升的十年和更长期的预测。越来越多的人一致认为，斯韦茨冰川不稳定，很容易坍塌。然而，对质量损失率的预测存在重大分歧，一些研究表明，从世纪到千禧年的大规模撤退，而另一些研究则预测了更具灾难性的解体。这些分歧是重大的，因为Thwaite和邻近冰川的快速解体可能会引发或加速西南极冰盖的大部分崩塌，对未来几十年全球平均海平面上升产生影响。目前，由于缺乏可靠的冰层破裂和解体模型，以及冰山破裂和气候变化之间的相互作用，预测斯韦茨冰川的冰消失率受到了阻碍。这项研究解决了这一重大知识差距，其动机是需要改进对政策和规划至关重要的海平面预测。此外，科学家对海平面上升预测的有用性的断言与利益相关者对这项工作的可用性的看法之间也存在差距。该项目也旨在解决这一差距，确定广大利益攸关方社区可以访问和使用的信息，同时积极与附近社区学院和学区的代表性不足的社区接触，让社区大学生参与研究。由于难以理解和预测控制冰盖稳定性的崩解和动力过程，西南极冰盖(特别是斯韦茨冰川)预计的海平面上升速度具有很大的不确定性。人们对冰解过程、冰盖稳定性和气候之间的联系知之甚少，这加剧了这种不确定性。为了解决这些不确定性，该项目试图使用一种新的冰动力学模型套件来明确解决可能导致Thwaites冰川退缩和坍塌的过程。该模型包括能够模拟破裂和冰流耦合过程的离散元模型、三维全斯托克斯连续介质模型和大陆尺度冰-动力学模型(BISICLES)。冰-动力学模式将与海洋强迫模式套件耦合，包括简单的羽流模式、中等复杂的两层海洋模式和全3D区域海洋模式。这一分层办法将使用高保真过程模型来提供信息并限制低阶模型的顺序，以便将更好的理解外推到更大的尺度上，并有可能从根本上减少海洋冰盖崩塌和相关海平面上升速度的不确定性。大规模建模方法将在开源的BISICLES冰动力学模型中进行测试和实施，并通过“冰化包”向其他研究人员公开。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project contributes to the joint initiative launched by the U.S. National Science Foundation (NSF) and the U.K. Natural Environment Research Council (NERC) to substantially improve decadal and longer-term projections of ice loss and sea-level rise originating from Thwaites Glacier in West Antarctica. There is growing consensus that Thwaites Glacier is unstable and vulnerable to collapse. However, there is significant disagreement in projections of rates of mass loss, with some studies suggesting century to millennial scale retreat and others forecasting more catastrophic disintegration. These disagreements are significant because rapid disintegration of Thwaites and adjacent glaciers could potentially trigger or accelerate collapse of significant portions of the West Antarctic Ice Sheet with implications for global mean sea-level rise in the coming decades. Predicting rates of ice loss from Thwaites Glacier is currently hampered by a lack of reliable models of ice fracture and breakaway--called iceberg calving--and the interactions between calving and climate change. This study addresses this major knowledge gap, and is motivated by the need to improve sea-level projections critical for policy and planning. Moreover, there is also a gap between what scientists assert about the usefulness of sea-level rise predictions and stakeholder's perceptions of the usability of that work. This project is also geared to address this gap, by identifying the information that is accessible and usable to a broad community of stakeholders whilst proactively engaging with under-represented communities at nearby community colleges and school districts, engaging community college students in research. Projected rates of sea-level rise from the West Antarctic Ice Sheet (and Thwaites Glacier in particular) have large uncertainties due to difficulties in understanding and projecting the calving and dynamic processes that control the ice-sheet stability. This uncertainty is magnified by the poorly understood connection between calving processes, ice-sheet stability and climate. To address these uncertainties, this project seeks to explicitly resolve the processes that could cause retreat and collapse of Thwaites Glacier using a novel ice-dynamics model suite. This model suite includes a discrete element model capable of simulating coupled fracture and ice-flow processes, a 3D full Stokes continuum model, and the continental scale ice-dynamics model (BISICLES). Ice-dynamics models will be coupled to an ocean forcing model suite including simple plume models, intermediate complexity 2-layer ocean models and fully 3D regional ocean models. This hierarchical approach will use high-fidelity process models to inform and constrain the sequence of lower-order models needed to extrapolate improved understanding to larger scales and has the potential to radically reduce uncertainty of rates of marine ice-sheet collapse and associated sea-level rise. The large-scale modeling approach will be tested and implemented within the open source BISICLES ice dynamics model and made publicly available to other researchers via a "calving package".This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.