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

这是华盛顿大学和沙漠研究所的首席研究人员共同提出的建议。他们将对降雪压实的时间和空间变化进行详细测量，以促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。他们将在格陵兰峰会的两个冬季和三个夏季使用钻孔光学地层学的概念进行详细测量，这将使用钻孔相机来记录墙壁的细节。这些细节可以随着时间的推移而被追踪，以确定垂直运动和应变，在浅层，这是由降雪压实所主导的。对降雪压实的定量了解对于遥感质量平衡研究很重要，该研究试图测量和解释冰盖高度的变化；冰层表面可能因积雪而上升，由于冰流和致密率增加而下降。对所有这三个过程的定量知识是必不可少的。有证据表明，致密化的速度经历了一个季节性周期，与温度的季节性周期有关。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困在冰中的。毛孔直到积雪深处才会闭合，这导致了冰的年龄和被困气体的年龄之间的差异。如果夏季高温对压实的影响比年平均温度更大，那么气龄/冰龄偏移量可能计算错误。对降雪致密化物理的更好理解将有助于解释这些记录。更广泛的影响--该项目将：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)使用冰面测高进行大规模质量平衡研究的调查人员将有一个实际测量降雪压实的新来源；2)建模者将能够验证和改进现有的降雪压实模型，进行详细的压实测量；3)新的热力学模型将使遥感研究能够根据积累和地表温度测量来估计随季节变化的降雪压实；4)研究捕获气泡气体用于古气候解释的调查人员将获得有关降雪致密和气体闭塞的物理新信息。通过研究生罗伯特·L·霍利的支持，整合研究和教育以促进教学、培训和学习。这项工作将为霍利的博士论文题目做出贡献，霍利将在首席研究员的指导下开展这一项目。通过与华盛顿州吉格港的中学科学和数学教师罗尔夫·特伦布莱和威斯康星州奇佩瓦瀑布的中学科学教师拉尔斯·朗的持续合作，加强K-12教育。这个项目让我们有机会让中学生参与一项科学努力的整个生命周期--从想法到假设，再到实验，形成结论和报告结果。鼓励通过面向非专业人士的项目网站广泛传播成果“，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.