ABSTRACT

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, to
experimentation, formulating conclusions and reporting results.
Encourage broad dissemination of results through a project website for the informed
layperson", supplementing our peer-reviewed journal articles.

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