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

The future trajectory of Earth's atmosphere depends on the response of land and ocean to a changing environment, especially the potential for substantial sustained carbon release in high latitude regions like the Arctic. A key question in understanding how the Earth system will respond is whether there are tipping points—global carbon cycle surprises—that will make the effects of environmental change such as sea-level rise, extreme weather, droughts, and impacts on agriculture occur faster than currently projected by models. Permafrost carbon, the remnants of plants, microbes, and animals accumulated in perennially frozen Arctic soil over thousands of years, currently holds twice as much carbon as the atmosphere, and could be such a tipping point. Release of just a fraction of this frozen carbon as carbon dioxide and methane into the atmosphere would significantly increase the rate of future global environmental change. Each additional ton of carbon released from the permafrost region to the atmosphere incurs additional costs to society and presents the challenge of requiring sustained long-term observations to quantify rates and unravel mechanisms in order to forecast change. This project will establish the Arctic Carbon and Climate (ACCLIMATE) permafrost carbon observatory, which will use field observations to measure carbon fluxes, and ecosystem carbon pools in a tundra ecosystem that is undergoing rapid and irreversible change due to regional warming. The project will also include training of a postdoctoral researcher and several undergraduate students, and outreach activities involving high school students and teachers.

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. Permafrost temperature at the Eight Mile Lake research watershed in Interior Alaska has been monitored for several decades starting before permafrost degradation began in the early 1990s. The impact of permafrost degradation on plants, microbes, and ecosystem carbon balance began to be documented in the early 2000s. The overall research plan will answer three focal questions: (1) Does warming and permafrost degradation cause a net release of carbon from the 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 that comprises the bulk of the soil carbon pool, and will this increase as thaw progresses; and (3) How does change in surface hydrology interact with thawing to control old carbon losses and the partitioning of carbon dioxide and methane, Carbon measurements, along with other key ecosystem variables collected by this observatory, will be organized for benchmarking regional and Earth System models, and coupled to that process through ongoing synthesis and model inter-comparison activities. These technical activities will be integrated with knowledge-transfer activities that link results to the broader scientific community, as well as to the broader public.