Modelling soil temperatures in northern peatlands.

Methane emissions from northern peatlands are strongly dependent on soil temperatures. Therefore, to predict methane emissions from northern peatlands under future climatic conditions, it is important to simulate the effect of these changing climatic conditions on peat temperatures. This article reports on the development and testing of two one-dimensional (1D) models used to simulate soil temperatures at shallow depths in a northern peatland. First, the HIP-Dlet (Heat in Peat – Dirichlet) model applies measured temperatures to the surface boundary of a conduction-based temperature model. Secondly, the HIP-Nmann (Heat in Peat – von Neumann) model simulates the surface boundary from standard meteorological measurements. The HIP-Dlet model provides a reasonable to good approximation of measured temperatures showing that heat transport processes within the soil are adequately simulated. The model does not simulate an advective liquid heat flux. However, only substantial rainfall events (> 70 mm over 3 days) during the study period had any significant effect on model error. Errors in the HIP-Nmann model were of a similar magnitude to the HIP-Dlet model. Errors in the HIP-Dlet model resulted predominantly from errors in the measured soil temperatures. Errors in the HIP-Nmann were due to errors in the measured soil temperatures and the inaccurate simulation of the surface boundary condition. The development of future peatland temperature models should, therefore, focus on the simulation of the surface boundary condition, particularly the parameterisation of the surface resistance that is shown here to produce significant errors in the modelled soil temperatures. [ABSTRACT FROM AUTHOR]