ABSTRACT

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2)

As the Arctic warms two-to-three times faster than the global average, the duration and intensity of melting is generally increasing on the surface of the Greenland ice sheet. About 90% of ice sheet is covered by compacted snow that is slowly transitioning into glacier ice. This aged and dense snow is called ?firn? and forms a porous layer that is many tens of meters thick. Much of the meltwater generated from the surface of the firn layer infiltrates into the underlying open pore space of the firn and refreezes. However, as this porous layer absorbs more melt it becomes warmer, denser, and filled with ice layers, which reduces its ability to absorb additional melt. Therefore, the thermal and structural transformation that Greenland's firn layer is presently undergoing has important implications for the ice sheet's capacity to retain future melt. This project is directly observing firn evolution with a network of instruments installed within the firn layer and with ice cores sampling the firn. The observational data collected by this project provides on-the-ground documentation of firn conditions needed to develop and test models and remote sensing tools for large-scale investigations of changes to the Greenland ice sheet. Future transformation of the firn layer will govern how much surface melt is retained locally on the ice sheet and how much runs off, thereby impacting hydrologic conditions of the ice sheet and surrounding regions, ocean salinity, and sea level rise.

The researchers will install and maintain an observation network along a transect of the Greenland ice sheet to directly measure the state and transformation of firn properties. Repeat sampling of firn cores and instrumentation extending from the surface to 25 meters depth will yield the observational datasets needed by multiple scientific communities: firn temperature, density and ice content, densification rate, surface boundary processes (radiation, snow accumulation, temperature), and ice velocity. The network will yield 4-5 full-year records in this five-year Arctic Observing Network project. The project will provide comprehensive datasets for process-level investigations, testing climate model simulations of firn processes, and interpreting satellite-based measurement of surface elevation change. The project will engage and support a relatively large number of undergraduate and graduate students at R2 institutions with field research experiences and real-world classroom learning. Outreach activities will target three groups poorly represented in cryospheric science: 1) local and Indigenous residents of Greenland; 2) American Indian undergraduate students; and 3) economically disadvantaged school children.

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.

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