Modeling Carbon Accumulation and Permafrost Dynamics of Northern Peatlands Since the Holocene

Northern peatlands are a large C stock and often act as a C sink, but are susceptible to climate warming. To understand the role of peatlands in the global carbon-climate feedback, it is necessary to accurately quantify their C stock changes and decomposition. In this study, a process-based model, the Peatland Terrestrial Ecosystem Model, is used to simulate pan-Arctic peatland C dynamics from 15 ka BP to 1990. To improve the accuracy of the simulation, spatially explicit water run-on and run-off processes were considered, four different pan-Arctic peatland extent data sets were used, and a spatially explicit peat basal date data set was developed using a neural network approach. The model was calibrated against 2055 peat thickness observations and the parameters were interpolated to the pan-Arctic region. Using the model, we estimate that, in 1990, the pan-Arctic peatlands soil C stock was 396–421 Pg C, and the Holocene average C accumulation rate was 22.9 g C·m−2 yr−1. Our estimated peat permafrost development history generally agrees with multi-proxy-based paleo-climate data sets and core-derived permafrost areal dynamics. Under Anthropocene warming, in the freeze-thaw and permafrost-free regions, the peat C accumulation rate decreased, but it increased in permafrost regions. Our study suggests that if current permafrost regions switch to permafrost-free conditions in a warming future, the peat C accumulation rate of the entire pan-Arctic region will decrease, but the sink and source activities of these peatlands are still uncertain.