NSF Award
2424218
Over half the Earth’s soil carbon resides in permafrost soils, defined as ground frozen for two years or longer, that are rapidly thawing at high latitudes. The cascading effects of this thaw include surface changes that threaten infrastructure, wholesale ecological change, and the release of carbon dioxide into the atmosphere, all of which may be irreversible. Understanding potential future changes in these environments requires critical information about the modern variability of sediment, ground-ice, and carbon in permafrost soils, as well as past changes that have influenced their distribution. However, past permafrost changes -- including the effects of hillslope erosion on carbon and ice storage -- are under-explored, especially on upland hillslopes that represent 45% of the permafrost-covered region of Alaska. In this project, researchers will measure the variability of soil, ground-ice, and carbon across selected hillslopes in Interior Alaska to understand how topography, sediment movement, and underlying geology influence permafrost distribution. In addition, this project will use a new combination of cutting-edge geochemical measurements to quantify permafrost evolution, from tens of thousands of years ago to the modern day. This work will shed light on fundamental geologic processes that control the resilience and vulnerability of ground-ice and carbon in permafrost landscapes – knowledge critical to understanding future change. In addition, these research activities will be combined with student training, public engagement, and documentary film to teach, inspire, and engage diverse groups in STEM.<br/><br/>Over half the belowground terrestrial organic carbon resides in permafrost soils that are rapidly thawing at high latitudes. Yet, permafrost environments display both vulnerability and resilience to changes, subject to interactions among ground ice, liquid water movement, and plant community succession. These interactions are strongly influenced by geomorphic processes that form and modify the geologic substrate in which permafrost develops. However, few studies explicitly measure these combined controls on permafrost evolution at a hillslope scale or consider them on the long timescales over which soils develop - limiting our understanding of the resilience of ice and carbon under changing environmental and climate conditions. To fill these knowledge gaps, the researchers will quantify how century to millennial-scale hillslope geomorphic processes influence the storage of ice and carbon in permafrost soils. They will target the role of geologic substrate and topography in mediating these processes and quantify their spatiotemporal expression in the subsurface architecture of ice, sediment, and carbon across hillslope systems in central Alaska. This project will study the long-term evolution of permafrost soils using a suite of geochemical tools, including 14C and luminescence to date sediment deposition; meteoric 10Be of sedimentary layers to measure soil residence times; and 234U/238U activity ratios to determine ground ice residence times. Their combined data will quantify spatiotemporal feedbacks among sediment movement, ground ice stability, and carbon storage within these hillslope systems. This research expands on past studies to shed light on fundamental hillslope processes that regulate the resilience and vulnerability of ice and carbon in permafrost landscapes. Research activities are coupled with student training, public engagement, and STEM media in the form of documentary film to support education and expand the representation and belonging of underrepresented students in STEM.<br/><br/>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.
