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

我的NSERC Discovery Grant研究项目的首要目标是开发一个强大的量化框架，以评估内陆水域在从地方到区域再到全球的景观碳和温室气体(GHG)预算中的作用。虽然二氧化碳通常是湖泊向大气排放碳的主要形式，但甲烷(CH4)的较高变暖潜力使它们对辐射强迫的影响大致相等。然而，考虑到甲烷相对于二氧化碳的生物地球化学循环的更复杂性质，对甲烷对温室气体总排放量的贡献的估计要多变得多，约束也很差。该提案的具体目标侧重于甲烷和目标1)测试描述沉积物CH4产生及其在沸腾通量和扩散通量之间分配的新模型，2)建立广泛湖泊上沉积物CH4产生与其他湖泊特征(特别是营养状况和温度)之间的定量关系，3)继续开发新的物理-生物地球化学耦合模型(PB-GHG)，并使用多湖和湖内方法进行验证。4)应用PB-GHG模型来评估加拿大湖泊的温室气体足迹在过去70年中发生了多大变化，以及在不同的气候变化和富营养化情景下可能进一步变化多少。这些项目结合我们以前的工作，将为更好地预测湖泊中CH4的动态提供最全面的框架。

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.