Closing the Water Vapor Exchange Budget Between the Ice Sheets and Free Atmosphere

As the Arctic warms faster than the rest of the planet, understanding the Greenland ice sheet response to changing climate ? and the associated effect on sea level rise - is important for policy and mitigation strategies. A variety of satellite and surface tools currently exist to help understand snow accumulation and the loss of ice from outlet glaciers or melting, but the magnitude of water vapor exchange between the interior ice sheet and the atmosphere remains essentially unknown. This vapor flux could potentially be a very large factor in calculating the mass gain or loss of the ice sheet. Vapor flux occurs either by addition to the ice surface through vapor deposition and condensation or losses due to sublimation. This project seeks to utilize Unmanned Aerial Vehicles, commonly referred to as drones, for collecting atmospheric water vapor samples to constrain vapor flux on the Greenland Ice Sheet. A remote-controlled sampling pod containing multiple air-capture chambers and environmental sensors will be retrofitted to a commercially available multi-copter drone and flown above the ice surface to collect samples. Upon landing, the atmospheric samples will be analyzed for water isotopes, which are variations of water molecules with different molecular weights that can, for example, provide evidence of vapor flux into or away from the ice sheet. The goal of this project is to use drone-captured data to address major gaps in the understanding of frozen water storage on the Greenland ice sheet, which could reduce uncertainty in estimates of global sea level rise. The data can also be used to improve satellite algorithms used for high-latitude measurements of water isotopes; to improve general circulation models; and improve meteorological understanding of the atmosphere in general. Further, these data may also substantiate the current understanding of long-term temperature records recovered from water isotopes of polar ice cores. Initial testing and atmospheric measurements using the drone-sampling unit will occur in Summer 2018 at an ice core camp in Northeast Greenland. A second deployment in 2019 will allow for improvements to the drone-sampling unit, and a possible deployment of a fixed wing drone aircraft, for measurement of high-resolution data across the 4-month summer field season.

This project will result in the first drone retrofitted with a water vapor sampling pod, which can be directly analyzed in the field following flight. In doing so, the project stands to provide the first detailed and high-resolution airborne measurements of water vapor isotopes in the critical atmospheric boundary layer just above the Greenland Ice Sheet. This region is typically too expensive and dangerous for manned-flight missions, and balloon release experiments have proven logistically burdensome with limited scientific returns. This study brings together researchers from the fields of Aerospace Engineering and Geochemistry. Students and researchers will receive drone pilot training through a Federal Aviation Administration accredited class. Undergraduate and graduate students will receive laboratory training to assist in processing and interpreting the data. A near real-time blog for public viewing and outreach will be available during field operations, which will include field updates, selected data, photography, and film. Public lectures and scientific talks will further disseminate the knowledge learned during this project. As the technology for this project progresses, it could be transferred to other projects, such as detection of fugitive emissions from oil and gas wells or to measure methane release in regions of thawing permafrost.

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.