NSF-NERC: THwaites Offshore Research (THOR)

该项目有助于美国国家科学基金会（NSF）和英国联合发起的联合倡议。自然环境研究理事会（NERC）将大幅改善对南极洲西部Thwaites冰川造成的冰损失和海平面上升的十年期和长期预测。 过去25年的卫星观测表明，思韦茨冰川正在迅速变薄和加速变薄。在同一时期，冰川从坐在海底过渡到漂浮的Thwaites接地线已经退缩。海洋学研究表明，这些变化的主要驱动力是来自深海的温水入侵，这些温水在浮冰架下流动，导致基底融化。卫星观测的时间不足以确定像斯韦茨这样的大型冰川如何对海洋或大气的长期和短期变化作出反应。因此，需要从前卫星时代的冰川变化的记录，以建立一个整体的了解冰川的行为。沉积在后退的接地线和更远的近海的海底沉积物包含了冰川和邻近海洋变化的长期记录。另一个大的未知数是海底地形，以及它如何影响向陆流动的温水与思韦茨冰川的相互作用，并影响其稳定性。因此，该项目的重点是斯韦茨冰川近海海底以及冰川和周围海洋沉积物中所含的过去冰川和海洋变化记录。通过对当前接地线的跨学科调查，包括提取温水入侵的十年至千年变化记录，确定前卫星时代的地线迁移历史，并限制控制温水流向地线的测深路径。保存在海底的沉积记录和冰川地貌将使我们能够重建驱动因素的变化以及冰川在一系列时间尺度上对这些变化的反应，从而提供可用于启动和评估模型可靠性的参考数据。这些数据将进一步深入了解对海洋冰盖动力学知之甚少的过程的影响。该项目将包括一整套海洋和冰下陆架研究活动，目的是确定思韦茨冰川接地线向海的边界条件，获取变化的外部驱动因素的记录，增进对导致思韦茨冰川崩塌的过程的了解，并确定接地线迁移和冰川底部条件的过去变化历史。这些目标将通过对海底进行高分辨率地球物理调查和使用船载设备对从思韦茨冰川接地线向海的内大陆架采集的岩心中的沉积物进行分析来实现，和从冰架下面使用通过热水钻孔部署在冰架上的取芯器。该奖项反映了NSF的法定使命，并通过使用基金会的学术价值和更广泛的影响评审标准。

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. Satellite observations extending over the last 25 years show that Thwaites Glacier is rapidly thinning and accelerating. Over this same period, the Thwaites grounding line, the point at which the glacier transitions from sitting on the seabed to floating, has retreated. Oceanographic studies demonstrate that the main driver of these changes is incursion of warm water from the deep ocean that flows beneath the floating ice shelf and causes basal melting. The period of satellite observation is not long enough to determine how a large glacier, such as Thwaites, responds to long-term and near-term changes in the ocean or the atmosphere. As a result, records of glacier change from the pre-satellite era are required to build a holistic understanding of glacier behavior. Ocean-floor sediments deposited at the retreating grounding line and further offshore contain these longer-term records of changes in the glacier and the adjacent ocean. An additional large unknown is the topography of the seafloor and how it influences interactions of landward-flowing warm water with Thwaites Glacier and affects its stability. Consequently, this project focuses on the seafloor offshore from Thwaites Glacier and the records of past glacial and ocean change contained in the sediments deposited by the glacier and surrounding ocean.Uncertainty in model projections of the future of Thwaites Glacier will be significantly reduced by cross-disciplinary investigations seaward of the current grounding line, including extracting the record of decadal to millennial variations in warm water incursion, determining the pre-satellite era history of grounding-line migration, and constraining the bathymetric pathways that control flow of warm water to the grounding line. Sedimentary records and glacial landforms preserved on the seafloor will allow reconstruction of changes in drivers and the glacial response to them over a range of timescales, thus providing reference data that can be used to initiate and evaluate the reliability of models. Such data will further provide insights on the influence of poorly understood processes on marine ice sheet dynamics. This project will include an integrated suite of marine and sub-ice shelf research activities aimed at establishing boundary conditions seaward of the Thwaites Glacier grounding line, obtaining records of the external drivers of change, improving knowledge of processes leading to collapse of Thwaites Glacier, and determining the history of past change in grounding line migration and conditions at the glacier base. These objectives will be achieved through high-resolution geophysical surveys of the seafloor and analysis of sediments collected in cores from the inner shelf seaward of the Thwaites Glacier grounding line using ship-based equipment, and from beneath the ice shelf using a corer deployed through the ice shelf via hot water drill holes.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.