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。虽然人们的注意力都集中在南极西部冰盖沿海边缘正在发生的快速变化上，但获得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方法。西南极冰盖是否在最后一次间冰期（约130，000至116，000年前）崩溃，当时气温略高于今天，仍然是南极冰川学中未解决的主要问题。大力士冰穹（Hercules Dome）是位于东南极洲和西南极洲冰盖交汇处的冰分水岭。它是记录西南极冰盖变化的冰川学和气候影响的理想地点。该项目将确定大力神圆顶是否由于两个冰盖的海拔变化而经历了流量的重大变化。该项目还将确定赫拉克勒斯圆顶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西南极冰盖是否在这一时期崩溃。该项目将支持两名早期职业研究人员，并培训华盛顿大学的学生。研究结果将通过与钻冰项目办公室、华盛顿大学在西雅图举办的年度极地科学周末以及艺术与科学合作的外联项目进行交流。该项目将研究东南极冰盖和西南极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。 冰分裂提供了一个独特的机会，以评估过去的冰流的稳定性。 冰流的低偏应力和非线性导致稳定冰分水岭下的内部层中出现拱形（“雷蒙德隆起”）。 该信息可用于确定稳定冰流的持续时间。由于缓慢的水平冰流速度，冰鸿沟也保存了旧冰与内部分层，反映了过去的流动条件所造成的鸿沟迁移。大力士冰穹是一个冰分水岭，它的位置很好，可以保留东南极冰盖和西南极冰盖过去几何形状变化的信息。这个圆顶也是最有希望恢复冰芯的位置，冰芯可以用来确定南极西部冰盖是否在最后一次间冰期崩溃。有限的冰穿透雷达数据收集沿着以前的科学表面导线显示保存完好的冰内地层和证据暗示雷蒙德凹凸，但以前的调查不够广泛，允许彻底的特点或确定过去的变化冰动力学。该项目将进行一项专门的调查，以绘制冰内地层和冰下地形以及赫拉克勒斯圆顶的基础特性。该项目将使用地基冰穿透雷达1）成像内部层和冰盖基底界面，2）准确测量冰内衰减，3）确定冰内垂直应变率。雷达数据将与GPS观测相结合，以获得详细的地形和表面速度，并建立冰流模型，以限制基础特征和过去冰流的历史。该奖项反映了NSF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.