NSF-NERC: Melting at Thwaites Grounding Zone and its Control on Sea Level (THWAITES-MELT)

NSF-NERC：思韦茨接地区的融化及其对海平面的控制（THWAITES-MELT）

• 批准号: 1739003
• 负责人: David Holland
• 金额: $ 216.5万
• 依托单位: New York University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-04-01 至 2024-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1739003&HistoricalAwards=false
• 关键词: NSF; NERC; Melting; Thwaites; Grounding

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. The fate of the West Antarctic Ice Sheet (WAIS) is one of the largest uncertainties in projections of sea-level change. Thwaites Glacier (TG) is a primary contributor to sea-level rise and its flow is accelerating. This faster flow is a response to reduced buttressing from its thinning, floating ice shelf, and is ultimately caused by ocean-driven melting. The degree to which costly and geopolitically-challenging sea-level rise will occur therefore hangs to a large extent on ice-ocean interactions beneath such Antarctic ice shelves. However, the Thwaites system is not sufficiently well understood, exposing a significant gap in our understanding of WAIS retreat, its ocean-driven forcing, and the consequences for sea level. The chief regulators of TG's retreat are ice and ocean processes in its grounding zone, the location where the ice flowing from inland goes afloat. Ice and ocean processes at this precise locale are central to our understanding of sea-level rise, yet key variables have not been constrained by observation. Model projections of TG's future display extreme sensitivity to melting in the grounding zone and how that melting is applied. Equally-credible melt rates and grounding-zone glaciological treatments yield divergent trajectories for the future of West Antarctica, ranging from little change to large-scale ice sheet collapse with a half a meter or more of sea-level rise. The enormous uncertainty in outcome stems from the lack of observations in this critical grounding zone region. The enhanced understanding of melting of TG's ice shelf that will come from this project's focused observational program will be built into state-of-the-art coupled ice-sheet and ocean models. These physics-rich, high-resolution models will allow the potential sea-level contribution of TG to be bounded to an unprecedented degree.This project will enable global and regional climate modelers to make a substantial improvement to projections of future ocean conditions over the continental shelf by providing physics-based projections of TG's sea-level contribution. The team proposes a suite of integrated activities: (1) multi-year oceanographic time series from beneath TG's ice shelf to quantify melting processes that need inclusion in ocean models, with a strong focus on the grounding zone, (2) analogous measurements on the glacier to validate processes governing grounding-line retreat, (3) coupling of these in situ measurements with novel, high-resolution space-borne observations, (4) building this new understanding into state-of-the-art ocean (MIT General Circulation Model and Imperial College Ocean Model) and ice sheet (WAVI) models to correctly simulate the TG system, (5) coupling the models and running with realistic present-day ocean forcing to project the state of TG basin over the next hundred years. The international team will use a range of techniques, from the well-established, such as using a hot-water drill to instrument the ice column and water column in the grounding zone, through to the cutting-edge, such as deploying a borehole deployable remotely operated vehicle to survey the grounding zone, and using phase-coherent radar to monitor ice strain and basal melt rates. The outcome of the project will be a more complete understanding of the TG system in the critical zone extending from a few kilometers inland of the grounding line, through the grounding zone, and out under the ice shelf.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.

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。西南极冰盖(WAIS)的命运是海平面变化预测中最大的不确定性之一。斯韦茨冰川(Tg)是海平面上升的主要贡献者，而且它的流动正在加速。这种更快的流动是对其变薄的漂浮冰架支撑力减少的反应，最终是由海洋驱动的融化造成的。因此，代价高昂且具有地缘政治挑战性的海平面上升的程度在很大程度上取决于南极冰架下的冰与海洋的相互作用。然而，对Thwaites系统的了解还不够充分，暴露了我们对WAIS撤退、其海洋驱动的强迫以及对海平面的影响的理解上的巨大差距。TG退缩的主要调节因素是其接地区的冰和海洋过程，这是从内陆流出的冰漂浮的位置。在这个精确的地点，冰和海洋过程是我们理解海平面上升的核心，但关键变量并没有受到观测的限制。TG未来的模型预测显示，对接地区的融化以及熔化的应用方式非常敏感。同样可信的融化速度和地面冰川学处理方法为南极洲西部的未来提供了不同的轨迹，从几乎没有变化到海平面上升半米或更多的大规模冰盖崩溃。结果的巨大不确定性源于在这一关键的接地区区域缺乏观测。这个项目的重点观测项目将增强对TG冰架融化的理解，这将被构建到最先进的冰盖和海洋耦合模型中。这些物理丰富的高分辨率模式将使Tg对海平面的潜在贡献达到前所未有的程度。该项目将使全球和区域气候模型人员通过提供Tg对海平面贡献的基于物理的预测，对大陆架上未来海洋状况的预测做出实质性改进。该团队提出了一套综合活动：(1)来自TG冰架下的多年海洋时间序列，以量化需要包括在海洋模型中的融化过程，重点是接地区，(2)对冰川的模拟测量，以验证控制接地线后退的过程，(3)将这些现场测量与新的高分辨率空间观测相结合，(4)将这种新的理解建立在最先进的海洋(麻省理工学院通用环流模型和帝国理工学院海洋模型)和冰盖(WAVI)模型中，以正确模拟TG系统，(5)将模式与现实的现代海洋强迫耦合运行，预测未来百年的Tg盆地状态。国际小组将使用一系列技术，从成熟的技术，例如使用热水钻机测量接地区的冰柱和水柱，到使用尖端技术，例如部署钻孔可展开的遥控运载器来勘测接地区，以及使用相位相干雷达监测冰的应变和基本融化速度。该项目的成果将是对关键区域中的TG系统有更全面的了解，该区域从接地线内陆几公里处延伸，穿过接地区，并在冰架下。该奖项反映了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。

项目成果

Rapid glacier retreat rates observed in West Antarctica

• DOI: 10.1038/s41561-021-00877-z
• 发表时间: 2022-01
• 期刊: Nature Geoscience
• 影响因子: 18.3
• 作者: P. Milillo;E. Rignot;P. Rizzoli;B. Scheuchl;J. Mouginot;J. Bueso-Bello;P. Prats-Iraola;L. Dini