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

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。在过去的三十年里，斯韦茨冰川一直在加速和扩大。Thwaites会以多快的速度解体，或者它多快会找到一个新的稳定状态，这已经成为关于西南极冰盖的未来及其对未来海平面上升的贡献的一些最重要的问题，在未来几十年到几个世纪乃至更长的时间里。该项目将依赖于三个独立的冰流数值模型，再加上一个海洋环流模型，以(1)提高我们对冰与底层基岩之间的相互作用的理解，(2)分析冰川对外部变化的敏感性，(3)评估可能导致Thwaites崩塌的过程，以及最重要的是，(4)预测Thwaites的未来冰损失。通过提供基于一套冰-海洋耦合模型的预测，该项目还将评估模型项目中的不确定性。该项目将使用三个独立的冰盖模型：冰盖系统模型、UA和STREAMICE，与麻省理工学院大气环流模型的海洋环流模型相耦合。该小组首先将重点放在冰解、冰破坏和基面滑度等关键物理过程的表示上，这些过程要么没有包括在以前的冰流模型工作中，要么没有得到很好的描述。然后，该小组将量化不同拟议的外部变化驱动因素(例如，海洋导致的冰架变薄、冰架固定点的丧失)的相对作用，并探索Thwaites冰川的稳定机制，目的是确定区分稳定和不稳定的基准线后退的内部阈值。使用逆方法，该项目将从现有的雷达测量中产生新的物理上一致的高分辨率(300米)冰层厚度数据集。此外，该团队将生成关于冰速和海拔变化率的新的遥感数据集。这些将被用来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能够比以前更严格地受到数据的约束。由此产生的关于斯韦茨冰川对全球海平面近期影响的更可靠的模型预测可以为与政策相关的决策提供信息。这一奖项反映了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. 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.