Long-term ground heat flux and heat storage at a mid-latitude site

We analyzed a long-term (37 year) record of monthly average below-ground temperatures, at depths ranging from the surface down to 12.8 m, to determine the ground heat flux. Temperatures at all depths have increased over the period, evidence of a non-zero mean ground heat flux. Analysis indicates an average downward flux out of the root zone (below 1.6 m) over the period of approximately 1.1 MJ m(-2) year(-1). The corresponding average flux through the bottom plane of measurement has been approximately 0.22 MJ m(-2) year(-1), indicating that 20% of the heat storage during the period has been at depths greater than 12.8 m. Current representations of ground heat flux in global climate models are inadequate to realistically simulate these results. This warming, if it continues, could affect a range of biotic and abiotic below-ground processes.