LTREB Renewal: The Arctic Carbon and Climate (ACCLIMATE) Observatory: Tundra Ecosystem Carbon Balance and Old Carbon Loss as a Consequence of Permafrost Degradation

Permafrost- soil that remains frozen throughout the year- stores substantial quantities of carbon. Permafrost carbon is derived from the remnants of plants, microbes, and animals accumulated in frozen Arctic soil over thousands of years. However, permafrost is vulnerable to thawing with increasing temperatures. This project examines the dynamics of permafrost carbon at a long-term study in a tundra ecosystem in interior Alaska. The long-term measurements collected by this project are critical for a landscape understanding about the impact of permafrost carbon on climate. The Arctic Carbon and Climate (ACCLIMATE) permafrost carbon observatory uses field observations to measure carbon fluxes, carbon isotope ratios, and ecosystem carbon pools in a tundra ecosystem that is undergoing rapid and irreversible change due to regional warming. The project educates undergraduate students who are conducting research projects. The project also conducts outreach to Denali National Park through the Murie Science and Learning Center. This project will also interface with the broader science community through ongoing synthesis work organized by the Permafrost Carbon Network. This project is the second five years of a planned ten-year study. The research plan is designed to answer three questions: 1) Does warming and permafrost degradation cause a net release of carbon from the terrestrial ecosystem to the atmosphere, and how does the magnitude change over years to decades? 2) What proportion of this carbon release is derived from old carbon stored in the soil?, and 3) How does change in surface hydrology interact with thawing to control old carbon losses through carbon dioxide and methane? The central hypothesis is that the transfer of carbon to the atmosphere will occur as a result of permafrost thaw and the microbial decomposition of organic carbon. Permafrost may act as an accelerating feedback to climate change if the old carbon that forms the bulk of the soil pool is respired to the atmosphere following permafrost thaw. Ultimately, the research will test this feedback loop in an important Arctic ecosystem. 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.