Collaborative Research: Improving Model Representations of Antarctic Ice-shelf Instability and Break-up due to Surface Meltwater Processes

冰架是冰川在陆地上的漂浮延伸。它们包围着南极洲75%的面积，在调节内陆冰川融化到海洋的速度方面发挥着重要作用，而海洋融化会导致海平面上升。据观察，这些冰架表面的融水会导致冰架弯曲和断裂，在某些情况下，还会发生大规模的崩塌事件。例如，2002年拉森B冰架几乎完全崩塌被认为是由2000多个地表湖泊在短短几周内的排水造成的。在南极洲的许多冰架上可以观察到大面积的池塘。随着大气温度的升高，表面融水引起的冰架破裂事件预计将在面积范围和频率上增加。然而，对这类事件的未来预测缺乏准确性，因为没有大规模的冰盖模型能够真实地模拟表面融水引起的冰架破裂的过程。该项目旨在通过开发大陆尺度冰盖和海平面系统模型（ISSM）的新组件来解决当前建模的局限性，该组件将能够模拟地表融水引起的弯曲、断裂和大规模冰架破裂。通过将该模型与一系列未来气候变化情景相结合，该项目旨在更准确地估计南极洲在本世纪剩余时间及以后对未来全球海平面上升的贡献。为了实现项目的最终步骤，即为冰盖和海平面系统模型（ISSM）开发一个新的模型组件，该团队将首先开发一个冰架水文-流动-弯曲-断裂的耦合过程尺度模型（H3F模型）。这是必要的，因为与ISSM等大陆冰盖模型所捕获的相比，冰架崩塌的物理过程通常发生在更精细的时间和空间尺度上。一旦H3F模型被开发出来，它将被用来量化地表融水过程、冰流、粘弹性弯曲和水力压裂之间的关系。该团队将通过开发一种利用机器学习的H3F模型统计模拟器，将这些关系转化为冰盖尺度。这种多物理场建模方法旨在为小尺度和大陆尺度的地表融水引起的冰架崩塌这一具有计算挑战性的问题提供新的进展。该项目的更广泛影响将包括通过开发儿童网络应用程序进行公众教育和参与，与芝加哥的艺术家团体进行互动，以及开发ISSM的外展网页，以促进在一系列未来气候情景下南极洲冰架崩塌事件的交互式可视化。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。

Ice shelves are the floating extensions of glaciers on land. They surround 75 percent of Antarctica and have an important role in regulating the rate that inland glacier ice is lost to the ocean, which leads to sea-level rise. Meltwater that ponds on the surfaces of these ice shelves has been observed to cause ice shelves to flex and fracture, and, in some cases, to experience large-scale collapse events. For example, the near-complete collapse of the Larsen B Ice Shelf in 2002 is thought to have been caused by the drainage of over 2000 surface lakes during just a number of weeks. Extensive ponding is observed on many of Antarctica’s ice shelves. As atmospheric temperatures increase, surface meltwater-induced ice-shelf breakup events are expected to increase in areal extent and frequency. However, future predictions of such events lack accuracy because no large-scale ice-sheet model is able to realistically simulate the processes involved in surface-meltwater-induced ice-shelf breakup. This project aims to address the current modeling limitation by developing a new component for the continental-scale Ice-sheet and Sea-level System Model (ISSM) that will be capable of simulating surface meltwater-induced flexure, fracture, and large-scale ice-shelf break-up. By forcing the model with a suite of future climate-change scenarios the project aims to deliver more accurate estimates of Antarctica’s contribution to future global sea-level rise over the remainder of this century and beyond.To achieve the project’s ultimate step of developing a new model component for the Ice-sheet and Sea-level System Model (ISSM), the team will first develop a coupled process-scale model of ice-shelf hydrology-flow-flexure-fracture (the H3F model). This is required because the physics involved in ice-shelf collapse typically occurs on finer temporal and spatial scales than captured by continental ice-sheet models such as ISSM. Once the H3F model is developed, it will be used to quantify relationships between surface meltwater processes, ice flow, viscoelastic flexure, and hydrofracture. The team will translate these relationships to the ice-sheet scale by developing a machine-learning-leveraged statistical emulator of the H3F model. This approach towards multi-physics modeling aims to provide new inroads to the computationally challenging problem of surface meltwater-induced ice-shelf collapse at both small- and continental-scales. Broader impacts of the project will include public education and engagement through development of a children’s web application, interaction with a Chicago-based artist collective, and development of ISSM’s outreach webpage to facilitate interactive visualizations of Antarctica ice-shelf collapse events under a range of future climate scenarios.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.