RAPID Proposal: Constraining kinematics of the Whillans/Mercer Ice Stream Confluence

在过去的一千年里，南极洲西部的简单海岸经历了重大的冰川变化。几个冰流——快速移动的冰流与缓慢移动的冰接壤——存在于这个地区，流入罗斯冰架。惠兰斯冰流的长期减速似乎正在发生，这正在影响惠兰斯和默瑟冰流之间的区域。然而，这种减速的一致性以及由此导致的两股冰流之间剪切边界的变化是未知的。该项目的目标是量化过去十年中观测到的变化，并了解导致这些变化的动态过程。作为一个RAPID项目，它的附带好处和驱动因素是测试一种方法，用于评估在陡峭的速度梯度区域中裂缝将在哪里发展。这种方法不仅有利于2018-19年的短期现场项目规划，也有利于未来的现场工作和穿越计划。该团队将使用遥感特征跟踪技术来确定过去10多年来剪切带位置的瞬态速度模式和变化。该速度时间序列将被纳入一个大尺度冰盖模型，以根据可能的区域冰通量情景估计下个世纪冰盖对边界条件变化的敏感性。该方法是该团队最近进行的工作的延伸，该工作有望预测表明活跃冰川剪切边缘的高应变率变化区域。最终目标是描述合并冰流随时间的流场特征，并研究侧向边界迁移。这将有助于更好地理解剪切边缘对冰架和冰川上稳定性的控制。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 Siple Coast in West Antarctica has undergone significant glacier changes over the last millenium. Several ice streams--rapidly moving streams of ice bordered by slow-moving ice--exist in this region that feeds into the Ross Ice Shelf. A long-term slowdown of Whillans Ice Stream appears to be occurring, and this is affecting the zone between the Whillans and Mercer Ice Streams. However, the consistency of this slowdown and resulting changes to the shear margin between the two ice streams are unknown. The goal of this project is to quantify the observed changes over the past decade and understand the dynamic processes that cause them. A collateral benefit of and driver for this as a RAPID project is to test a method for assessing where crevassing will develop in this zone of steep velocity gradients. Such a method may benefit not only near-term field-project planning in the 2018-19 field season, but also planning for future fieldwork and traverses.The team will use remote sensing feature-tracking techniques to determine transient velocity patterns and shifts in the shear-zone location over the last 10-plus years. This velocity time series will be incorporated into a large-scale ice-sheet model to estimate ice-sheet susceptibility to changing boundary conditions over the next century based on likely regional ice-flux scenarios. This approach is an extension of recent work conducted by the team that shows promise for predicting areas of changing high strain rates indicative of an active glacier shear margin. The ultimate objectives are to characterize the flow field of merging ice streams over time and investigate lateral boundary migration. This will provide a better understanding of shear-margin control on ice-shelf and up-glacier stability.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.