Melting Permafrost: A Massive Source of CO2

On a winter day in the mid-afternoon, a researcher samples Eight Mile Lake in Alaska with an ice auger to assess levels of dissolved carbon and to collect samples for radiocarbon dating. These measurements will help quantify the lateral movement of carbon from tundra ecosystems experiencing permafrost thaw, and will help determine the overall loss of carbon from these ecosystems.

Climate change is altering the world in which we live. At present, increasing greenhouse gases responsible for climate change are largely a result of human activities: much of the additional carbon dioxide in the atmosphere is the result of fossil fuel burning and the conversion of forests and other ecosystems to agriculture.

However, there is the possibility that climate change alters the natural cycling of carbon in ecosystems that are far removed from direct human influence. The permafrost carbon pool contains more than 100 times the current annual input of carbon dioxide into the atmosphere from human activity, and thresholds at the freezing point indicate that abrupt changes are possible. Emissions of just a fraction of this permafrost carbon pool could have significant implications for the pace of future climate change.

Twice as much carbon is contained in the soils and permafrost of northern ecosystems as compared to that currently contained in the atmosphere. Because of the size and nature of the permafrost carbon pool, decomposition of previously frozen, old, organic carbon is one of the most likely terrestrial-ecosystem feedbacks to increase temperatures during climate change in a warmer world.

This project uses radiocarbon measurements as a unique fingerprint for detecting the loss of old soil carbon in combination with an ecosystem-scale field manipulation to determine what controls the release of permafrost carbon. This research is focused on ecosystem carbon cycling, primarily driven by the uptake of carbon from the air by plants, and the release of carbon back to the atmosphere via respiration. However, some of the carbon movement from ecosystems occurs via the hydrologic cycle as dissolved carbon leaves the soils in water that enters lakes and streams.

Read more about this work at: http://www.nsf.gov/news/news_summ.jsp?cntn_id=114865 and see a narrated slideshow with stunning imagery from this research effort in the Arctic at: http://www.nsf.gov/news/newsmedia/permafrost/.

- Ted Schuur, University of Florida