The past, present and future greenhouse gas (GHG) footprint of lakes: from biogeochemical processes to large scale upscaling

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The overarching goal of my NSERC Discovery Grant research program is the development a robust quantitative framework to assess the role of inland waters in landscape carbon and greenhouse gas (GHG) budgets, from local to regional to global. While CO2 is typically the dominant form in which lakes emit carbon to the atmosphere, the higher warming potential of methane (CH4) renders their impact on radiative forcing about co-equal. However, given the more complex nature of the biogeochemical cycling of methane relative to CO2, estimates of the contribution of CH4 to total GHG emissions is much more variable and poorly constrained. The specific objectives of this proposal are focused on methane and aim 1) to test a new model describing sediment CH4 production and its partitioning between ebullitive and diffusive fluxes, 2) to establish the quantitative relationship between sediment CH4 production and other lake characteristics (in particular, trophic status and temperature) on a broad set of lakes, 3) continue the development of a novel coupled physical-biogeochemical model (PB-GHG) and its validation using both a multi-lake and within-lake approaches, 4) apply the PB-GHG model to evaluate by how much the GHG footprint of Canadian lakes has changed over the past 70 years and by how much it is likely to change further under different scenarios of climate change and eutrophication. Together, these projects, combined our previous work, will provide the most comprehensive framework to better predict the dynamics of CH4 in lakes.