Using JULES to Model the Congo Peatlands

The Cuvette Centrale swamp forest around the Congo river has the most extensive peatland complex in the tropics, but due to its remoteness the peat was only recently discovered.  The international project CongoPeat, which includes scientists from the Republic of the Congo and the Democratic Republic of the Congo and works with the local people of the Cuvette Centrale, is studying the peatlands to determine how they formed and the possible threats since it is vital that the peat is preserved.  While the peatlands are at least 20,000 years old the peat is thin compared to other tropical peatlands of similar age.  The JULES land surface model has been used with a reconstruction of the past annual rainfall and a simulation of other climate variables with the HadCM3 model to simulate the development of the peatlands.  The model results support the hypothesis that a long period of reduced rainfall a few thousand years ago lead to a large loss of peat and recreate the age-depth profiles of the peat in measured soil cores including the feature called a “ghost interval”.  This confirms that a constant high water table is needed to keep decomposition of the peat to a minimum and hence preserve the peatlands.  JULES was then run with future climate projections from five global climate models to simulate how the peatlands could change up to 2100.  In most projections the increased temperatures lead to increased evapotranspiration, lower water tables and increased decomposition of peat.  In most cases peat is lost overall, particularly when rainfall is also reduced further lowering the water tables, in-spite of increased CO₂ concentration increasing the amount of vegetation and litterfall while reducing the amount of plant transpiration. The risk to the peatland Carbon is greater at higher levels of global warming.