EAGER: Extending Greenland glacier observations using newly-discovered aerial photographs

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Three military airborne campaigns (USAF: 1940s-1960s, USCG: 1970s, USN: 1970s-1980s) acquired tens of thousands of aerial photographs of Greenland. These recently-located photographs can yield insight into ice-sheet wide glacier behavior prior to satellite observations but have not yet been digitized or used for science. Currently, lack of ice sheet-wide observations prior to the 1980s limits our ability to model the long-term evolution of outlet glacier dynamics. The research team will digitize historic images from the 1940s to 1980s, render glacier surface elevations and terminus positions for the perimeter of Greenland, and estimate surface velocities where the data permits. By providing glacier information further back in time, this new historical dataset can be used to improve constraints needed to model glacier dynamics which will further advance accuracy in predictive models of glacier response to climate change. The workflow and products will be available in a public repository for the community to access and a tutorial will be designed to help researchers repeat the process for other historical images. The earliest ice sheet-wide surface elevation maps were produced using data from the 1980s. This project will extend the historical record by including Greenland-wide glacier images from the 1940s and 1970s and from the 1950s and 1960s for a large number of outlet glaciers. The methodology includes: digitizing the air photo film negatives, geolocating the photo centers using a combination of military flight index maps and field notes, and processing the images using structure-from-motion (SfM) photogrammetry techniques to generate surface elevations. The real-world coordinates are manually extracted localized peaks from present-day elevations of stable terrain (e.g., exposed bedrock). This methodology has been successfully carried out using historical air photos from Antarctica. Upon the completion of this project, the raw digital data and rendered products with accuracy estimates will be made accessible for public distribution. By extending the temporal scale of Greenland outlet glacier dynamics, this new historical dataset can improve constraints used in modeling glacier dynamics which will further advance accuracy in predictive models of glacier response to climate change. Raw data and derived products, including surface elevation, orthorectified images, and velocities, will be archived at the Arctic Data Center and results will be shared with QGreenland and GHub to expand the audience. A tutorial will also be designed to allow others to reproduce the results and apply the methodology to other historical datasets.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.