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

在过去的千年里，南极洲西部的Siple海岸经历了巨大的冰川变化。几个冰流--快速移动的冰流与缓慢移动的冰接壤--存在于这个流入罗斯冰架的区域。惠兰冰流的长期放缓似乎正在发生，这正在影响惠兰冰流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个冰流之间剪切边缘的变化尚不清楚。该项目的目标是量化过去十年中观察到的变化，并了解导致这些变化的动态过程。作为一个快速项目，这一项目的一个附带好处和推动力是测试一种方法，以评估在这个速度梯度陡峭的区域哪里会出现裂缝。这种方法可能不仅有利于2018-19年外业赛季的短期外业项目规划，还可以规划未来的外业工作和导线。该团队将使用遥感特征跟踪技术来确定过去10多年剪切带位置的瞬时速度模式和位移。这一速度时间序列将被纳入大规模冰盖模式，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。这一方法是该团队最近工作的延伸，该工作显示了预测高应变率地区的前景，高应变率表明冰川剪切边缘活跃。最终目标是描述随时间合并的冰流的流场，并研究横向边界迁移。这将有助于更好地了解冰架和冰川上稳定性的剪切边缘控制。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.