Ice Dynamics at the Intersection of the West and East Antarctic Ice Sheets

南极冰盖对气候变化的反应是预测全球海平面上升的一个核心问题。虽然人们的注意力集中在南极西部冰盖沿海边缘正在发生的快速变化上，但获取过去冰盖和气候变化的记录是限制冰盖在千年时间尺度上如何变化的唯一途径。南极西部冰原是否在末次间冰期（~13万至11.6万年前）崩解，当时的温度比今天稍高，这仍然是南极冰川学的一个主要未解问题。大力神穹窿是位于南极东部和南极西部冰原交汇处的冰分水岭。它处于记录南极西部冰盖变化的冰川学和气候影响的理想位置。该项目将确定由于两个冰盖高度的变化，Hercules Dome的流量是否发生了重大变化。该项目还将确定大力神丘是否是恢复末次间冰期气候记录的合适地点。这些记录可以用来确定南极西部冰盖是否在那段时间坍塌。该项目将支持两名早期职业研究人员，并在华盛顿大学培训学生。研究结果将通过与冰钻项目办公室、华盛顿大学西雅图年度极地科学周末以及艺术科学合作协调的外展项目进行交流。该项目将发展南极东部和西部冰盖交汇处的冰动力学历史，并确定该地点是否适合进行深冰取芯作业。冰缝提供了一个独特的机会来评估过去冰流的稳定性。低偏应力和冰流的非线性导致在稳定的冰分裂下的内层形成拱形（“雷蒙德隆起”）。这些信息可用于确定稳定冰流的持续时间。由于水平冰流速度缓慢，冰分裂也保留了内部分层的旧冰，反映了分裂迁移引起的过去流动条件。大力神穹窿是一个冰分水岭，它的位置很好，可以保留南极东部和西部冰盖过去几何形状变化的信息。这个圆顶也是最有希望找到冰芯的地方，可以用来确定南极西部冰盖是否在最后一次间冰期坍塌。在之前的科学地表穿越中收集到的有限的破冰雷达数据表明保存完好的冰川地层和雷蒙德隆起的证据，但之前的调查还不够广泛，无法彻底表征或确定过去冰动力学的变化。该项目将进行一项专门的调查，以绘制冰川地层学和冰下地形以及大力神丘的基础性质。该项目将使用地面探冰雷达，1)对内层和冰盖基底界面进行成像，2)精确测量冰川衰减，3)确定冰川垂直应变率。雷达数据将与GPS观测数据相结合，以获得详细的地形和地表速度，以及冰流模型，以约束过去冰流的基本特征和历史。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。

The response of the Antarctic ice sheet to climate change is a central issue in projecting global sea-level rise. While much attention is focused on the ongoing rapid changes at the coastal margin of the West Antarctic Ice Sheet, obtaining records of past ice-sheet and climate change is the only way to constrain how an ice sheet changes over millennial timescales. Whether the West Antarctic Ice Sheet collapsed during the last interglacial period (~130,000 to 116,000 years ago), when temperatures were slightly warmer than today, remains a major unsolved problem in Antarctic glaciology. Hercules Dome is an ice divide located at the intersection of the East Antarctic and West Antarctic ice sheets. It is ideally situated to record the glaciological and climatic effects of changes in the West Antarctic Ice Sheet. This project will establish whether Hercules Dome experienced major changes in flow due to changes in the elevation of the two ice sheets. The project will also ascertain whether Hercules Domes is a suitable site from which to recover climate records from the last interglacial period. These records could be used to determine whether the West Antarctic Ice Sheet collapsed during that period. The project will support two early-career researchers and train students at the University of Washington. Results will be communicated through outreach programs in coordination the Ice Drilling Project Office, the University of Washington's annual Polar Science Weekend in Seattle, and art-science collaboration.This project will develop a history of ice dynamics at the intersection of the East and West Antarctic ice sheets, and ascertain whether the site is suitable for a deep ice-coring operation. Ice divides provide a unique opportunity to assess the stability of past ice flow. The low deviatoric stresses and non-linearity of ice flow causes an arch (a "Raymond Bump") in the internal layers beneath a stable ice divide. This information can be used to determine the duration of steady ice flow. Due to the slow horizontal ice-flow velocities, ice divides also preserve old ice with internal layering that reflects past flow conditions caused by divide migration. Hercules Dome is an ice divide that is well positioned to retain information of past variations in the geometry of both the East and West Antarctic Ice Sheets. This dome is also the most promising location at which to recover an ice core that can be used to determine whether the West Antarctic Ice Sheet collapsed during the last interglacial period. Limited ice-penetrating radar data collected along a previous scientific surface traverse indicate well-preserved englacial stratigraphy and evidence suggestive of a Raymond Bump, but the previous survey was not sufficiently extensive to allow thorough characterization or determination of past changes in ice dynamics. This project will conduct a dedicated survey to map the englacial stratigraphy and subglacial topography as well as basal properties at Hercules Dome. The project will use ground-based ice-penetrating radar to 1) image internal layers and the ice-sheet basal interface, 2) accurately measure englacial attenuation, and 3) determine englacial vertical strain rates. The radar data will be combined with GPS observations for detailed topography and surface velocities and ice-flow modeling to constrain the basal characteristics and the history of past ice flow.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.