Modelling the impact of climate change on future carbon dynamics of northern peatlands

Northern peatlands, spanning across vast regions of the northern hemisphere, are critical carbon reservoirs essential for global carbon cycling and climate regulation. Their dual role as long-term atmospheric carbon dioxide (CO2) sinks and the largest natural source of methane (CH4) in the northern hemisphere allows them to accumulate more carbon than they emit, helping to mitigate the rise in atmospheric CO2 levels. However, they face significant threats from ongoing climate change, while the local response to climate change is divided. The potential impacts of increasing temperatures, altered precipitation patterns and shifts in hydrology have the capacity to accelerate decomposition rates and release stored carbon into the atmosphere, thereby exacerbating global warming. Conversely, the net productivity of peatland ecosystems also increases due to CO2 fertilization and prolonged growing seasons in northern latitudes. This study employs the dynamic global vegetation model LPJ-GUESS to analyse historical and future carbon dynamics of northern peatlands, aiming to reduce uncertainty surrounding peatland carbon stocks by evaluating the historical model results and assessing the fate of four northern peatlands under CMIP5 projections (RCP2.6 and RCP8.5). The project does not only identify the temporal and spatial patterns of the peatland carbon stocks and greenhouse gas emissions at these sites but also quantify how these patterns are in response to climatic drivers. Evaluation against available datasets and literature reveals underestimations in modelled annual carbon sink capacities) and overestimated CH4 emissions, introducing uncertainties in future carbon balance assessments. Despite limitations, the trend in future carbon stocks suggests a potential reduction across Canadian sites under RCP8.5, while the sites demonstrate resilience under RCP2.6. The high emissions scenario (RCP8.5) projects Stordalen and Mer Bleue to potentially transition into carbon sources by 2100, while NEP trends in Scotty Creek and Attawapiskat indicate robust carbon sink capacities, with varying methane emissions driven by changing hydrology and vegetation shifts. These findings underscore the complex interplay of climate, vegetation composition, and permafrost thawing in shaping future peatland carbon dynamics. Despite model underestimations of carbon sink capacities, the observed trends in net ecosystem productivity (NEP) offer valuable insights into potential future trajectories. Future research should prioritize refining model inputs and incorporating bias-corrected historical data to enhance simulation accuracy and deepen our understanding of peatland responses to climate change.

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