Department of Earth & Environmental Sciences
MULT-SCALE, MULTI-METHOD CHARACTERIZATION OF METHANE CYCLING IN NORTHERN PEATLANDS
Although peatlands cover only ~3% of the Earth's land surface they are an important reservoir in the carbon cycle, accounting for about 33% of the global soil carbon pool. Previous estimates suggest that peatlands account for 5 to 10% of methane (CH4) flux to the atmosphere. Release of biogenic gases from peatlands occurs by diffusion, transport through vascular plants, and episodic ebullition events. Oxidation of dissolved methane reduces the release of methane by diffusion, but the transit time of bubbles released via ebullition is too short for extensive oxidation to occur, i.e. ebullition releases effectively increase the greenhouse gas potential of peatlands. Understanding the pathways by which CH4 is released to the atmosphere is therefore more important than understanding just CH4 production rates alone.
Ebullition remains poorly quantified experimentally and inadequately represented by quantitative models. Ebullition exhibits high spatiotemporal variability such that sudden episodic events are difficult to capture and quantify. In this talk, I describe how non-invasive geophysical methods, combined with automated chamber measurements, have been developed to gain new insights into both the importance of ebullition fluxes from peatlands and the mechanisms by which gas is transported in a peatland and released to the atmosphere. The results demonstrate the importance of variations in atmospheric pressure and hydrology in regulating ebullition fluxes from peatlands, and also highlight the role of the peat fabric in regulating releases. The work suggests that CH4 flux estimates from peatlands need to be updated in global climate models to account for the spatiotemporal variability of ebullition.