Detecting the Lit Fuse of the Arctic's Carbon Bomb
Abstract
Permafrost soils in the Arctic contain vast quantities of ancient organic matter. If thawed, the decomposition of this aged organic carbon would release the greenhouse gases CO2 and CH4 to the atmosphere, fueling a positive feedback between permafrost thaw and global warming. The term “carbon bomb” has been used to describe this process, primarily in the popular press but also within journals such as Science and Nature and by NSF. Yet unlike a real bomb, its detonation might initially be hard to detect, as spatial heterogeneity in the terrestrial landscape leads to a variety of responses, even over relatively small spatial scales, and it would unfold over relatively long timescales. We suggest that interannual trends in the age of dissolved organic carbon (DOC) in Arctic streams and rivers during the late-summer period of maximum active layer depth may be a sensitive indicator of permafrost thaw and incipient detonation of the Arctic’s carbon bomb, at least at the watershed scale. That is, if warming is causing widespread increases in active layer depth, we would predict that the age of DOC in Arctic streams and rivers would be increasing over time. Prior to this study, the oldest published DOC ages that we know of are approximately ~7000 years. Here we present data for small streams draining a permafrost exposure along the Kolyma River in northeast Siberia. In these streams, DOC concentrations were extremely high (100-340 mg/L) and DOC ages were exceptionally old (~20,000-30,000 years), indicating the potential for ancient DOC to be mobilized and transported downstream when permafrost thaws. The data do not exist to know whether temporal trends in DOC age are already presenting an unambiguous signal of widespread terrestrial change in the Arctic, but we suggest that observations of stream water DOC age may be one of our more powerful means of identifying significant feedbacks in the Arctic’s carbon cycle and will foreshadow the widespread detonation of the Arctic’s carbon bomb.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMGC52A..01H
- Keywords:
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- 0428 BIOGEOSCIENCES / Carbon cycling;
- 0702 CRYOSPHERE / Permafrost;
- 0744 CRYOSPHERE / Rivers;
- 1615 GLOBAL CHANGE / Biogeochemical cycles;
- processes;
- and modeling