NSFPLR-NERC: THwaites Offshore Research (THOR)

人们一致认为，暖水穿过大陆架的入侵是当代思韦茨冰川退缩的主要驱动力，这是未来全球海平面快速上升的最大风险。通过对当前接地线向海方向的一系列调查，包括提取暖水入侵的千年代际变化记录和卫星时代前接地线迁移的历史，以及限制控制暖水流向接地线的水深路径，可以显著降低Thwaites冰川未来模型预测的不确定性。保存在海底的沉积记录和冰川地貌将允许在一定时间尺度上重建驱动因素的变化和冰川对它们的响应，从而提供可用于启动和评估模型可靠性的参考数据。这类数据还将有助于深入了解鲜为人知的过程对海洋冰盖动力学的影响。拟议的项目包括一套综合的海洋和冰下架研究活动，旨在建立Thwaites冰川接地线向海的边界条件，获得变化的外部驱动因素的记录，提高导致Thwaites冰川崩塌过程的知识，并确定过去接地线迁移和冰川基地条件变化的历史。这些目标将通过对海底进行高分辨率的地球物理调查，并使用船载设备分析从Thwaites冰川接地线向海的内大陆架沉积物中收集的沉积物，以及通过热水钻孔在冰架下部署的覆盖物从冰架下收集的沉积物来实现。该项目将使用一套来自现代接地线向海的海洋地质和地球物理数据，得出驱动因素和卫星时代前退缩历史的记录，并确定控制思韦茨冰川退缩的关键边界条件。这些数据将用于解决关于斯韦茨冰川行为的三对假设。前两种假设探讨了温水入侵对冰川稳定性的影响，包括这种入侵的现代途径和20世纪由温水引发的退缩历史。第二组假设解决了冰下融水对Thwaites冰川稳定性的作用，使用现代沉积物通量率与岩心记录的沉积物通量率的比较来测试冰下融水输出的偶然性及其对冰川稳定性的影响。最后，第三对假设解决了床和冰架固定点的性质和地形对稳定接地线的作用。

There is a consensus that incursion of warm water across the continental shelf is the main driver ofcontemporary retreat of Thwaites Glacier, which presents the greatest risk of future rapid global sea-levelrise. Uncertainty in model projections of the future of Thwaites Glacier can be significantly reduced by arange of investigations seaward of the current grounding line, including extracting a record of decadal tomillennial variations in warm water incursion and the history of pre-satellite era grounding linemigration, and constraining the bathymetric pathways that control the flow of warm water to thegrounding line. Sedimentary records and glacial landforms preserved on the seafloor will allowreconstruction of changes in drivers and the glacier's response to them over a range of timescales, thusproviding reference data that can be used to initiate and evaluate the reliability of models. Such data willalso provide insights on the influence of poorly understood processes on marine ice sheet dynamics.The proposed project includes an integrated suite of marine and sub-ice shelf research activities aimed atestablishing boundary conditions seaward of the Thwaites Glacier grounding line, obtaining records ofthe external drivers of change, improving knowledge of processes leading to collapse of ThwaitesGlacier, and determining the history of past change in grounding line migration and conditions at theglacier base. These objectives will be achieved through high-resolution geophysical surveys of theseafloor and analysis of sediments collected in sediment cores from the inner shelf seaward ofthe Thwaites Glacier grounding line using ship-based equipment, and also from beneath theice shelf using a corer deployed through the ice shelf via hot water drill holes.This project will use a suite of marine geological and geophysical data from seaward of the moderngrounding line, to derive records of drivers and pre-satellite era retreat history, and determine keyboundary conditions that control Thwaites Glacier retreat. The data will be used to address three pairs ofhypotheses about the behavior of Thwaites Glacier. The first pair of hypotheses address the impact ofwarm-water incursions on glacial stability, both the modern pathways for such incursions and the 20thcentury history of warm-water initiated retreats. The second pair of hypotheses address the role ofsubglacial meltwater on Thwaites Glacier stability, using a comparison of modern sediment flux rates tothose recorded in cores to test the episodic nature of subglacial meltwater output, and of its influence onglacial stability. Finally, the third pair of hypotheses address the role the nature and topography of thebed and ice shelf pinning points have on stabilizing the grounding line.