Collaborative Research: P2C2: Contributions of northern cold-climate peatlands and lakes to abrupt changes in atmospheric methane during the last deglaciation

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The proposed research integrates studies in a range of disciplines (paleoecology, climate, biogeochemistry, geomorphology, geology) to understand the timing, magnitude, and overall contribution of northern cold-climate peatlands and lakes to rapid increases in atmospheric methane (CH4) concentrations (AMC) during the last deglaciation. The study will use comprehensive paleoecological records of northern peatland and lake development to document their past spatial and temporal patterns of CH4 emission. This will enable better prediction of future emissions from northern ecosystems, particularly as surface permafrost thaws under scenarios of climate warming. Specifically, the PIs propose to: (1) Synthesize new and existing peatland, thermokarst-lake, kettle-lake and other post-glacial lake initiation data, as well as compiling such data from regions that no longer support peatlands or permafrost, such as on formerly exposed continental shelf and along southern margins of ice sheets, to gain knowledge of timing of these AMC sources during the last deglaciation; (2) analyze new and existing peat macrofossil data to estimate past CH4 flux from northern high latitude peatland regions as they evolved from high- CH4 emitting fens to lower- CH4 emitting bogs during the Holocene; (3) use novel stable isotope approaches and 14C dating to constrain the magnitude and timing of permafrost-derived hydrogen and carbon in CH4 from northern peatlands and lakes that formed when ground ice melted; and (4) compare their bottom-up reconstructions of past CH4 emissions and their isotope values from peatlands and thermokarst lakes with top-down modeling of global atmospheric CH4 sources based on recent, higher resolution data of interhemispheric CH4 isotope (13C, D, 14C) gradients recorded in Greenland and Antarctic ice cores.Methane is a potent greenhouse gas. Its global warming potential is many times that of carbon dioxide. Therefore, in order to develop scenarios of future climate change, it is important to be able to estimate how much methane will be released to the atmosphere due to permafrost degradation. This project will constrain that number.