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

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.

本项目响应美国国家科学基金会（U.S. National Science Foundation, NSF）与英国自然环境研究理事会（U.K. Natural Environment Research Council, NERC）联合发起的倡议，旨在大幅提升对源自南极西部思韦茨冰川（Thwaites Glacier）的冰量损失与海平面上升的十年及更长期预测精度。
学界正逐步达成共识，认为思韦茨冰川处于不稳定状态且极易发生崩塌。但针对其冰量损失速率的预测却存在显著分歧：部分研究认为该冰川会在百年至千年尺度上发生退缩，另有研究则预测其会出现更具灾难性的解体。这些分歧影响重大，因为思韦茨冰川及其邻近冰川的快速解体，可能会触发或加速南极西部冰盖大片区域的崩塌，进而对未来数十年的全球平均海平面上升产生深远影响。当前，对思韦茨冰川冰量损失速率的预测受限于两大瓶颈：一是缺乏可靠的冰断裂与脱离模型——即冰山崩解（iceberg calving），二是未厘清崩解过程与气候变化之间的相互作用。
本研究旨在填补这一重大知识空白，其研究动机源于提升海平面预测精度的迫切需求——该预测对政策制定与规划工作至关重要。此外，在科学家对海平面上升预测实用性的论断，与利益相关方对该研究成果可用性的认知之间，仍存在显著鸿沟。本项目也致力于解决这一鸿沟：一方面要识别出能被广泛利益相关群体理解与使用的信息，另一方面将主动与附近社区学院及学区中代表性不足的群体开展互动，邀请社区学院学生参与科研工作。
由于难以理解并预测控制冰盖稳定性的冰山崩解与动力过程，南极西部冰盖（尤其思韦茨冰川）带来的海平面上升预测速率存在极大不确定性。而冰山崩解过程、冰盖稳定性与气候之间的关联机制尚未明确，进一步放大了这一不确定性。
为解决这些不确定性问题，本项目拟采用一套全新的冰动力学模型套件，对可能导致思韦茨冰川退缩与崩塌的过程进行明确解析。该模型套件包含可模拟断裂与冰流耦合过程的离散元模型、三维全斯托克斯（Stokes）连续介质模型，以及大陆尺度冰动力学模型（BISICLES）。冰动力学模型将与海洋强迫模型套件进行耦合，后者涵盖简单羽流模型、中等复杂度两层海洋模型以及全三维区域海洋模型。
这种层级化建模方法将采用高保真过程模型，为将改进后的认知外推至更大尺度所需的低阶模型提供依据与约束，有望从根本上降低海洋冰盖崩塌速率及相关海平面上升的不确定性。本大型尺度建模方法将在开源BISICLES冰动力学模型中进行测试与实现，并通过“崩解工具包（calving package）”向其他研究人员公开共享。
本奖项契合美国国家科学基金会的法定使命，且通过基金会的学术价值与更广泛影响评审标准评估，认定其值得获得资助。