NSF-NERC: Geological History Constraints on the Magnitude of Grounding Line Retreat in the Thwaites Glacier System

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。斯韦茨冰川系统对南极洲海平面上升的贡献占主导地位。预测这个系统在未来几十年将如何演变，从而预测它对海平面的可能贡献，需要详细了解它过去如何对气候和海洋条件的变化作出反应。该项目将通过建立上升的海洋海滩的年表，以及通过冰下钻探对目前被斯韦茨冰川覆盖的基岩进行采样和定年，在过去一万年中，斯韦茨冰川退缩的时间和持续时间，提供区域海平面变化的记录。与其他记录的气候和海洋学条件一起，这些将为过去到现在的模式模拟以及用于预测一系列气候情景下未来冰川变化的模式模拟提供边界条件。具体来说，该项目将检验该地区现有地质证据所暗示的假设，即目前思韦茨冰川系统的快速退缩是可逆的。该团队的目标是利用两种方法：1。为了重建全新世期间的相对海平面，它将绘制和确定整个松岛湾上升的海洋和海岸线沉积物的日期。海平面变化的时间限制将通过对地貌和沉积物中与过去海平面有遗传关系的有机物质（如贝壳碎片、海洋动物骨骼和企鹅粪便）进行放射性碳定年来提供。2. 为了获得过去接地线后退的地质证据，研究小组将对冰下基岩进行宇宙成因核素暴露测年。利用最近开发的用于冰下基岩回收的钻井系统，该团队将从Thwaites系统中冰层厚度与接地线位置动态相关的地点（特别是在Hudson Mountains和Mount Murphy附近）获得冰下基岩。对这些样品中显著的宇宙生成核素浓度的观察——研究小组将主要测量铍-10和原位碳-14——将为过去与接地线退缩有关的变薄事件以及它们的时间和持续时间的限制提供直接、明确的证据。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. The Thwaites Glacier system dominates the contribution to sea-level rise from Antarctica. Predicting how this system will evolve in coming decades, and thereby its likely contribution to sea level, requires detailed understanding of how it has responded to changes in climate and oceanographic conditions in the past. This project will provide a record of regional sea-level change by establishing chronologies for raised marine beaches as well as the timing and duration of periods of retreat of Thwaites Glacier during the past 10,000 years by sampling and dating bedrock presently covered by Thwaites Glacier via subglacial drilling. Together with climatic and oceanographic conditions from other records, these will provide boundary conditions for past-to-present model simulations as well as those used to predict future glacier changes under a range of climate scenarios. Specifically, the project will test the hypothesis--implied by existing geological evidence from the region--that present rapid retreat of the Thwaites Glacier system is reversible. The team aims to utilize two approaches: 1. To reconstruct relative sea level during the Holocene, it will map and date raised marine and shoreline deposits throughout Pine Island Bay. Chronological constraints on sea-level change will be provided by radiocarbon dating of organic material in landforms and sediments that are genetically related to past sea level, such as shell fragments, bones of marine fauna, and penguin guano. 2. To obtain geological evidence for past episodes of grounding-line retreat, the team will apply cosmogenic-nuclide exposure-dating of subglacial bedrock. Using drill systems recently developed for subglacial bedrock recovery, the team will obtain subglacial bedrock from sites where ice thickness is dynamically linked to grounding-line position in the Thwaites system (specifically in the Hudson Mountains, and near Mount Murphy). Observation of significant cosmogenic-nuclide concentrations--the team will primarily measure Beryllium-10 and in situ Carbon-14--in these samples would provide direct, unambiguous evidence for past episodes of thinning linked to grounding-line retreat as well as constraints on their timing and duration.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.