Collaborative Research: A Unique Opportunity for In-Situ Measurements of Seasonally-Varying Firn Densification at Summit, Greenland

这是华盛顿大学和沙漠研究所的主要研究人员合作提出的一项建议。他们将对冻土压实的时空变化进行详细测量，以推进对冰变形的认识和理解，并跨越不同的领域，包括遥感、雪形态和古气候学。他们将利用钻孔光学地层学的概念，在格陵兰峰的两个冬季和三个夏季进行详细的测量，该概念将使用钻孔相机记录岩壁的细节。随着时间的推移，这些细节可以被跟踪，以确定垂直运动和应变，这在浅层深处主要是由坚硬的压实。对冻土压实的定量了解对于遥感质量平衡研究非常重要，因为遥感质量平衡研究旨在测量和解释冰盖高度的变化；由于积雪的积累，地表会上升，而由于冰流和密度率的增加，地表会下降。这三个过程的定量知识是必不可少的。有证据表明，致密化的速度经历一个季节性循环，与温度的季节性循环有关。在解释冰芯捕获气体的古气候数据时，重要的是要知道气体实际上是在什么时候被捕获在冰中。这些孔隙直到冰芯深处才会关闭，这就导致了冰的年龄和被困气体的年龄之间的差异。如果夏季高温比年平均温度对压实的影响更大，那么气体年龄/冰期偏移量的计算可能不正确。对固体致密物理的更深入的了解将有助于对这些记录的解释。更广泛的影响-本项目将：加强冰川学、古气候学和遥感领域的研究和教育基础设施：1)利用冰面测高法进行大规模质量平衡研究的研究人员将获得实际测量雪压实度的新来源；2)建模者将能够通过详细的压实测量来验证和改进现有的压实模型；3)新的热力学模型将使遥感研究能够基于累积量和地表温度测量来估计季节性变化的铁屑压实；4)研究被困气泡用于古气候解释的研究将获得关于固体致密化和气体闭塞物理的新信息。通过研究生Robert L. Hawley的支持，整合研究和教育以促进教学、培训和学习。这项工作将成为Hawley博士论文的主题，他将在首席研究员的指导下开展该项目。通过与华盛顿州吉格港的中学科学和数学教师Rolf Tremblay和威斯康星州奇佩瓦瀑布的中学科学教师Lars Long的持续合作，加强K-12教育。这个项目让我们有机会让中学生参与科学研究的整个生命周期——从想法到假设，到实验，形成结论和报告结果。鼓励通过项目网站“为知情的外行”广泛传播结果，补充我们同行评议的期刊文章。

This is a collaborative proposal by Principal Investigators at the University of Washington and the Desert Research Institute. They will make detailed measurements of the temporal and spatial variations of firn compaction to advance knowledge and understanding of ice deformation and across different fields, including remote sensing, snow morphology, and paleoclimatology. They will make detailed measurements through two winter and three summer seasons at Summit Greenland using the concept of Borehole Optical Stratigraphy, which will use a borehole camera to record details of the wall. These details can be tracked over time to determine vertical motion and strain, which in the shallow depth is dominated by firn compaction. Quantitative understanding of firn compaction is important for remote-sensing mass-balance studies, which seek to measure and interpret the changing height of the ice sheet; the surface can rise due to snow accumulation, and fall due to ice flow and increased densification rates. Quantitative knowledge of all three processes is essential. Evidence suggests that the rate of densification undergoes a seasonal cycle, related to the seasonal cycle of temperature. When interpreting ice core trapped-gas data for paleoclimate, it is important to know at what point the gas was actually trapped in the ice. The pores do not close off until deep in the firn, leading to a difference between the age of the ice and the age of the trapped gas. If summer high temperatures have more impact on compaction than mean annual temperatures, the gas-age/ice-age offset might be incorrectly calculated. Greater understanding of firn densification physics will help the interpretation of these records. Broader Impacts- This project will: Enhance infrastructure for research and education in the glaciology, paleo-climatology, and remote-sensing community: 1) investigators working on large-scale mass-balance studies using ice-surface altimetry will have a new source of actual measurements of firn compaction; 2) modelers will be able to validate and improve existing models of firn compaction with detailed compaction measurements; 3) new thermo-mechanical models will allow remote-sensing studies to estimate seasonally-varying firn compaction based on accumulation and surface temperature measurements; and 4) investigators studying trapped bubble-gas for paleoclimate interpretation will have new information about the physics of firn densification and gas-occlusion. Integrate research and education to promote teaching, training, and learning through the support of a graduate student, Robert L. Hawley. This work will contribute to a PhD dissertation topic for Hawley, who will carry out this project under the direction of the Principal Investigator.Enhance K-12 education through ongoing collaboration with Rolf Tremblay, a middle school science and math teacher in Gig Harbor, Washington, and Lars Long, a middle school science teacher in Chippewa Falls, Wisconsin. This project gives us the opportunity to involve middle school students with the complete life cycle of a scientific endeavor- from idea to hypothesis, toexperimentation, formulating conclusions and reporting results. Encourage broad dissemination of results through a project website for the informedlayperson", supplementing our peer-reviewed journal articles.