Impacts of future climate change on soil frost in the midwestern United States

Historical observations indicate a shift toward shorter winters and increased average air temperatures in the midwestern United States. Furthermore, a rise in soil temperatures is likely to be enhanced under projections of increased air temperature; however, reduced snow cover during winter may lead to colder soil temperatures in the future. Cumulatively, these changes will affect cold season processes in the region. Therefore the impact of such changes on cold season processes were analyzed under two climate models (Geophysical Fluid Dynamics Laboratory version CM2.1.1 (GFDL) and UK Met Office Hadley Center Climate Model, version 3.1 (HadCM3)) and three scenarios (B1, A1B, and A2) by implementing the variable infiltration capacity land surface model from 1977 to 2099. Ensemble averages of the two models for the three scenarios indicated that both air temperature and precipitation would increase in the cold season (December-May), with the greatest increases projected under the A2 scenario by late in the 21st century (2070-2099). Also during this period, the median number of days when air temperature was below 0 C reduced in comparison to the base period (1977-2006) by 25, 35, and 38 days for the B1, A1B, and A2 scenarios, respectively. The number of freeze-thaw cycles increased in the south-central Wisconsin and the northern regions of Michigan by up to 3 cycles, while the duration of soil frost decreased by between 2 weeks and nearly 2 months during 2070-2099 with respect to the base period.