A major contributor to the current uncertainty regarding how carbon cycling in peatlands will respond to climate warming is the incomplete understanding of the production, storage and emission of free phase gas (FPG), a previously under-appreciated source of methane and carbon dioxide emissions to the atmosphere. It is increasingly clear that FPG production, storage and emission are regulated by hydraulic forcing, as well as the mechanical properties of the peat, i.e. that the carbon and water cycles in a peatland are intimately connected. The focus of this project is field-scale hydrological and hydrogeophysical research to further investigate the importance of recently invoked 'shallow' versus 'deep' peat models for the production, storage and emission of FPG in northern peatlands. Specific objectives of the project include [1] quantifying vertical variations in storage and release of methane with depth over a minimum six month time period at each of three locations within a peatland, [2] determining the hydrological forcing mechanisms that drive releases from both deep and shallow gas, [3] estimating spatial variations in storage and release as a function of subsurface heterogeneity, and [4] quantifying relative contributions of shallow versus deep gas to methane emissions from a northern peatland. This research will be conducted by coupling hydrogeological methods with novel chamber, geophysical and geodetic sensing technologies sensitive to FPG production, storage and emissions. The field site is Caribou Bog, a well-studied multi-unit peatland complex in central Maine. Empirical predictive models and simple mechanistic models will be developed to assess the relative importance of key forcing mechanisms on FPG emissions. Time-frequency analysis of time-series datasets will also be employed to improve understanding of likely forcing components regulating production, storage and release of FPG. This research will significantly advance our understanding of hydrological controls on FPG dynamics in northern peatlands, with important implications for the response of peatland carbon dynamics to climate change.
Northern peatlands globally cover more than 350 million ha and contain about one third of the terrestrially stored carbon. The fate of this carbon in response to continued climate warming is highly uncertain. Peatlands are also a source of atmospheric methane, a potent greenhouse gas that contributes to climate warming. This research will provide fundamental scientific knowledge needed to advance the understanding of the cycling of methane in peatlands, and how peatland hydrology controls the emission of methane from peatlands to the atmosphere. The work has direct societal relevance given the concerns about the environmental and economical affects of climate warming. In this project, Lois Stokes Alliance for Minority Participation undergraduate students will be exposed to a hands-on interdisciplinary research among three institutions. Furthermore, an international community of graduate students will participate in a student-focused session on methane cycling in northern peatlands at American Geophysical Union meetings. Community outreach in the vicinity of the Caribou Bog will occur via annual guided tours using the Orono Bog Boardwalk that served +30,000 visitors in 2009.
