Collaborative Research: Disentangling runoff- and Terminus-driven Velocity Variations of Fast Flowing Outlet Glaciers

极地冰盖的冰流失是下个世纪全球平均海平面上升的最大预期贡献。冰层流失速度的一个基本控制因素是冰从冰盖内部流到冰盖边缘的速度。在格陵兰冰盖内部，冰流对液态水(“径流”)的输入做出反应，这会影响冰如何滑过下面的基岩。在格陵兰边缘的海洋终端“出口冰川”，冰以随季节变化的速度流入海洋。这种强烈的季节变化使得确定液态水输入对流速的影响程度变得更加困难。确定海洋驱动的冰流变化与融化驱动的冰流变化的相对强度，对于用于预测未来冰川流失的计算机模型至关重要。很难以一致的方式评估这些因素，因为它们在多个时间尺度上运行，因此需要不同的观察方法，而不能直接比较。这项建议试图解决三个关键的激励问题：(Q1)径流如何在几小时到几年的时间尺度上影响出口冰川流量？(Q2)冰川几何形状如何影响对径流的响应？(Q3)径流和终点驱动的速度变化如何相互作用？为了解决这些问题，PIS将利用最近开发的灵活时间序列分析方法，将大型海洋末端出口冰川的新现场观测与来自多个来源的新获得的卫星数据结合起来。多元统计分析和理想化的数值模型实验将检验径流驱动和末端驱动的变化之间的假设反馈，并将观测工作与更一般的设置联系起来。PIS将开发开放源码软件，允许其他研究人员复制他们对任何冰川的遥感和现场数据的分析。团队中的博物馆专业人员将与PI协调开发一个关于北极冰川变化驱动因素的特别展览；在北方阿拉斯加大学博物馆初步安装后，该展览将用于参观其他北极博物馆。该奖项反映了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。

Ice loss from the polar ice sheets is the largest anticipated contribution to global mean-sea-level rise in the coming century. A fundamental control on the rate of ice loss is how fast ice flows from ice sheet interiors out to the edges. In the interior of the Greenland Ice Sheet, ice flow responds to liquid water (“runoff") input, which affects how the ice slides over the bedrock beneath. At ocean-terminating "outlet glaciers” around the edges of Greenland, ice flows into the ocean with speed that varies by season. That strong seasonal variation makes it more difficult to determine the extent to which liquid water input is affecting the flow speed. Identifying the relative strength of ocean-driven versus melt-driven ice flow variations is essential for computer models used to forecast future ice loss. It has been difficult to assess those factors in a consistent way because they operate over multiple time scales, thus requiring different methods of observation that could not be directly compared.This proposal seeks to address three key motivating questions: (Q1) How does runoff affect outlet glacier flow over timescales of hours to years?; (Q2) How does glacier geometry affect the response to runoff?; and (Q3) How do runoff- and terminus-driven velocity variations interact? To address these questions, the PIs will combine new field observations at a large marine-terminating outlet glacier with newly available satellite data from multiple sources, using recently developed methods for flexible time series analysis. Multivariate statistical analysis and idealized numerical model experiments will test hypothesized feedbacks between runoff-driven and terminus-driven changes, as well as connect the observational work to more general settings. The PIs will develop open-source software that allows other researchers to replicate their analysis for remote-sensing and in situ data obtained on any glacier. Museum professionals on the team will coordinate with the PIs to develop a special exhibit on the drivers of Arctic glacier change; after initial installation at the University of Alaska Museum of the North, the exhibit will be made available to tour other Arctic museums.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.