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

在即将到来的世纪，极地冰盖的冰损失预计将是全球平均海平面上升的最大原因。 控制冰损失速度的一个基本因素是冰从冰盖内部流到边缘的速度。 在格陵兰冰盖的内部，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。 在格陵兰岛边缘的海洋终端“出口冰川”，冰流入海洋的速度因季节而异。 这种强烈的季节性变化使得更难以确定液态水输入对流速的影响程度。 确定海洋驱动与融化驱动的冰流变化的相对强度对于用于预测未来冰损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，因此需要不同的观测方法，无法直接比较。本提案试图解决三个关键的激励问题：（Q1）径流如何影响出口冰川流量在几小时到几年的时间尺度？(Q2)冰川的几何形状如何影响对径流的响应？以及（Q3）径流和终端驱动的流速变化如何相互作用？为了解决这些问题，PI将结合联合收割机在一个大型海洋终端出口冰川的新的实地观测与新获得的卫星数据从多个来源，使用最近开发的灵活的时间序列分析方法。 多元统计分析和理想化的数值模型实验将测试径流驱动和终端驱动的变化之间的假设反馈，以及连接的观测工作，更一般的设置。 PI将开发开源软件，允许其他研究人员复制他们对任何冰川的遥感和原位数据的分析。 该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;在阿拉斯加大学北方博物馆进行初步安装后，该展览将提供给其他北极博物馆参观。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。

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.