NSF-NERC: PROcesses, drivers, Predictions: Modeling the response of Thwaites Glacier over the next Century using Ice/Ocean Coupled Models (PROPHET)

该项目是美国国家科学基金会（NSF）和英国自然环境研究委员会（NERC）联合发起的一项倡议的一部分，该倡议旨在实质性地改进西南极洲思韦茨冰川的冰损失和海平面上升的十年和长期预测。在过去的三十年里，斯韦茨冰川一直在加速和扩大。思韦茨冰盖崩解的速度有多快，找到新的稳定状态的速度有多快，已经成为南极西部冰盖未来的一些最重要的问题，以及它对未来几十年、几个世纪乃至更长时间内海平面上升的影响。该项目将依靠三个独立的冰流数值模型，再加上一个海洋环流模型来(1)提高我们对冰与下垫基岩之间相互作用的理解，(2)分析冰川对外部变化的敏感程度，(3)评估可能导致思韦茨冰川崩塌的过程，最重要的是，(4)预测未来思韦茨冰川的冰损失。通过提供基于一套耦合冰-海洋模型的预测，该项目还将评估模型预测的不确定性。该项目将使用三个独立的冰盖模型：冰盖系统模型、Ua模型和STREAMICE模型，并与麻省理工学院环流模型中的海洋环流模型相结合。研究小组将首先关注冰裂、冰损伤和基底滑动等关键物理过程的表现，这些在以前的冰流建模工作中要么没有包括在内，要么表现不佳。然后，该团队将量化不同提议的外部变化驱动因素的相对作用（例如，海洋引起的冰架变薄，冰架固定点的丧失），并探索思韦茨冰川的稳定状态，目的是确定区分稳定和不稳定接地线退缩的内部阈值。使用逆方法，该项目将从可用的雷达测量中获得新的物理一致的高分辨率（300米）冰厚数据集。此外，该小组将生成关于冰速和海拔变化率的新遥感数据集。这些将用于约束和验证数值模型，也将是有价值的独立数据集。这一过程将使数值模型比以前更严格地受到数据的约束。由此产生的关于思韦茨冰川近期对全球海平面影响的更可靠的模型预测可以为政策相关决策提供信息。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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. Thwaites Glacier has been accelerating and widening over the past three decades. How fast Thwaites will disintegrate or how quickly it will find a new stable state have become some of the most important questions of the future of the West Antarctic Ice Sheet and its contribution to sea-level rise over the next decades to centuries and beyond. This project will rely on three independent numerical models of ice flow, coupled to an ocean circulation model to (1) improve our understanding of the interactions between the ice and the underlying bedrock, (2) analyze how sensitive the glacier is to external changes, (3) assess the processes that may lead to a collapse of Thwaites, and, most importantly, (4) forecast future ice loss of Thwaites. By providing predictions based on a suite of coupled ice-ocean models, this project will also assess the uncertainty in model projections.The project will use three independent ice-sheet models: Ice Sheet System Model, Ua, and STREAMICE, coupled to the ocean circulation model of the MIT General Circulation Model. The team will first focus on the representation of key physical processes of calving, ice damage, and basal slipperiness that have either not been included, or are poorly represented, in previous ice-flow modelling work. The team will then quantify the relative role of different proposed external drivers of change (e.g., ocean-induced ice-shelf thinning, loss of ice-shelf pinning points) and explore the stability regime of Thwaites Glacier with the aim of identifying internal thresholds separating stable and unstable grounding-line retreat. Using inverse methodology, the project will produce new physically consistent high-resolution (300-m) data sets on ice-thicknesses from available radar measurements. Furthermore, the team will generate new remote sensing data sets on ice velocities and rates of elevation change. These will be used to constrain and validate the numerical models, and will also be valuable stand-alone data sets. This process will allow the numerical models to be constrained more tightly by data than has previously been possible. The resultant more robust model predictions of near-future impact of Thwaites Glacier on global sea levels can inform policy-relevant decision-making.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.