Modeling water table changes in boreal peatlands of Finland under changing climate conditions

A process-based model was developed and validated to predict the regional dynamics of the water table (WT) in peatlands under climatic forcing. The model detailed the water-energy feedbacks in the common SVAT (soil–vegetation–atmosphere transportation) model and specified the differences in processes in pristine fens, pristine bogs and drained peatlands. The spatiotemporal changes in the WT of the peatlands throughout Finland were computed based on 10 km × 10 km grids for the period 2000–2099. The calculations used country-scale data on vegetation, catchment topography and profiles of peat bulk density and water content in the three mire types. Furthermore, the ACCLIM climate scenarios representing the current climate and the changing climate were used to identify the climatic impacts on the WT throughout Finland.Sensitivity analysis showed that the WT drawdown in pristine fens was most sensitive to increases in temperature and/or decreases in precipitation, whereas the WT drawdown in drained peatlands was the most resistant to such changes. For all three mire types, a 10% increase in precipitation based on the current climate tended to offset the effect of a 2 °C warming on WT drawdown and a 20% increase in precipitation tended to offset the WT drawdown caused by a 6 °C warming. Based on the ACCLIM climate scenario, the model showed moderate changes in the annual values of the WT, which ranged from +0.2 ± 1.5 to −4.3 ± 0.93 cm. The changes were most noticeable during the period 2060–2099. The WT drawdown was more pronounced in late spring than in summer and autumn. Additionally, the WT drawdown was most significant in the western parts of the northern aapa-mire region, where the peatlands were mostly pristine, and the increase of precipitation was more limited than in other parts of the country. These results show that the pronounced spatiality and temporality in the WT changes should be considered in studies addressing how climate change will affect mire ecosystems in terms of C balance and GHG emissions.

► We modeled the dynamics of water table (WT) in the boreal peatlands of Finland. ► We estimated the effect of climate change on the peatland WT in Finland during period 2000–2099. ► The peatland WT will fall under the changing climate at national scale. ► The most drawdown of WT will occur in the western areas of middle Finland during period 2060–2099. ► The WT drawdown will be larger in pristine fens comparing to pristine bogs and drained peatlands.