NSF-NERC: Thwaites Interdisciplinary Margin Evolution (TIME): The Role of Shear Margin Dynamics in the Future Evolution of the Thwaites Drainage Basin

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。南极西部冰盖（WAIS）的崩塌可能会使全球海平面上升约5米（16英尺），科学界认为这是沿海环境和城市面临的最大风险。风险来自于WAIS的深海海洋环境。尽管自20世纪70年代初以来，科学家们就已经意识到这片冰盖的危险环境，但直到现在，几个大流域的冰流才经历了与潜在的不可逆转的解体相一致的动态变化。了解WAIS的稳定性和通过计算机模拟更准确地预测海平面上升是当今极地科学界面临的两个关键目标。该项目将通过以下方式直接实现这两个目标：(1)使用最先进的技术来观测Thwaites冰川快速变形的部分，这些部分可能对WAIS的未来演变有重要影响；(2)使用这些新的观测结果来改进用于预测未来海平面上升的冰盖模型。这个项目汇集了一个由英国和美国科学家组成的多学科团队。这种国际合作将导致对自然过程的新理解，这可能导致WAIS的崩溃，并将通过创建一个多学科的科学家网络来促进研究和教育的基础设施。该团队将指导3名博士后，培养4名博士生，并整合本科生参与该研究项目。该项目将测试一个总体假设，即剪切边缘动力学可能对斯韦茨流域冰流的未来演变施加强有力的控制。为了验证这一假设，研究小组将在斯韦茨冰川东部剪切边缘的两个地点建立一个冰观测站。研究小组认为，薄弱的地形控制使得这个剪切边缘容易受到向外迁移的影响，而且当斯韦茨的接地线后退时，可能会随着内陆冰的减少而突然跳跃。冰观测站的设计目的是对冰的性质，包括冰的变形速率、冰晶结构、冰的粘度、冰的温度、冰的含水量和基本融化速率，产生新的和全面的约束。冰观测站还将建立基础条件，包括表层和深层海洋沉积物（如果有的话）的厚度和孔隙度。此外，该小组将开发新的知识，重点是物理过程，包括直接评估这些过程运作的空间和时间尺度。利用无线检波器进行二维和三维地震调查。宽带地震仪网络将识别由裂缝和基底滑动引起的冰震。具有相控阵的自主雷达系统将产生快速变形的3D内层序列图像，同时也可能揭示基础水系统的几何形状。数据集将被纳入在不同空间尺度上开发的数值模型。一个将特别关注剪切边缘动力学，另一个将关注剪切边缘动力学如何影响整个流域的冰流。完成后，该项目旨在确认斯韦茨冰川的东部剪切边缘是否能像假设的那样快速迁移，如果是这样，本世纪及以后海平面上升的影响将是什么。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. Collapse of the West Antarctic Ice Sheet (WAIS) could raise the global sea level by about 5 meters (16 feet) and the scientific community considers it the most significant risk for coastal environments and cities. The risk arises from the deep, marine setting of WAIS. Although scientists have been aware of the precarious setting of this ice sheet since the early 1970s, it is only now that the flow of ice in several large drainage basins is undergoing dynamic change consistent with a potentially irreversible disintegration. Understanding WAIS stability and enabling more accurate prediction of sea-level rise through computer simulation are two of the key objectives facing the polar science community today. This project will directly address both objectives by: (1) using state-of-the-art technologies to observe rapidly deforming parts of Thwaites Glacier that may have significant control over the future evolution of WAIS, and (2) using these new observations to improve ice-sheet models used to predict future sea-level rise. This project brings together a multidisciplinary team of UK and US scientists. This international collaboration will result in new understanding of natural processes that may lead to the collapse of the WAIS and will boost infrastructure for research and education by creating a multidisciplinary network of scientists. This team will mentor three postdoctoral researchers, train four Ph.D. students and integrate undergraduate students in this research project.The project will test the overarching hypothesis that shear-margin dynamics may exert powerful control on the future evolution of ice flow in Thwaites Drainage Basin. To test the hypothesis, the team will set up an ice observatory at two sites on the eastern shear margin of Thwaites Glacier. The team argues that weak topographic control makes this shear margin susceptible to outward migration and, possibly, sudden jumps in response to the drawdown of inland ice when the grounding line of Thwaites retreats. The ice observatory is designed to produce new and comprehensive constraints on englacial properties, including ice deformation rates, ice crystal fabric, ice viscosity, ice temperature, ice water content and basal melt rates. The ice observatory will also establish basal conditions, including thickness and porosity of the till layer and the deeper marine sediments, if any. Furthermore, the team will develop new knowledge with an emphasis on physical processes, including direct assessment of the spatial and temporal scales on which these processes operate. Seismic surveys will be carried out in 2D and 3D using wireless geophones. A network of broadband seismometers will identify icequakes produced by crevassing and basal sliding. Autonomous radar systems with phased arrays will produce sequential images of rapidly deforming internal layers in 3D while potentially also revealing the geometry of a basal water system. Datasets will be incorporated into numerical models developed on different spatial scales. One will focus specifically on shear-margin dynamics, the other on how shear-margin dynamics can influence ice flow in the whole drainage basin. Upon completion, the project aims to have confirmed whether the eastern shear margin of Thwaites Glacier can migrate rapidly, as hypothesized, and if so what the impacts will be in terms of sea-level rise in this century and beyond.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.