Implementation and evaluation of a new methane model within a dynamic global vegetation model: LPJ-WHyMe v1.3

For the first time, a model that simulates methane emissions from northern peatlands is incorporated directly into a dynamic global vegetation model. The model, LPJ-WHyMe (LPJ-Wetland Hydrology and Methane), was previously modified in order to simulate peatland hydrology, permafrost dynamics and peatland vegetation. LPJ-WHyMe simulates methane emissions using a mechanistic approach, although the use of some empirical relationships and parameters is unavoidable. The model simulates methane production, three pathways of methane transport (diffusion, plant-mediated transport and ebullition) and methane oxidation. Two sensitivity tests were conducted, first to identify the most important factors influencing methane emissions and secondly to justify the choice of parameters. A comparison of model results to observations from seven sites revealed in general good agreement but also highlighted some problems. Circumpolar methane emissions for the period 1961–1990 were estimated to be between 40.8 and 73.7 Tg CH4 a-1.