Seasonal Soil Frost in the upper Mississippi River Basin

Seasonal soil frost can play a significant role in controlling energy and water fluxes through the winter and spring in the upper Mississippi River basin. Ice in the soil can impede the infiltration of spring melt and precipitation events, potentially leading to higher peak flows on regional streams. It also reduces soil moisture drainage, minimizing baseflow generation and groundwater recharge through the winter and yielding wetter soils in the spring. In terms of the land-surface energy balance, changes in soil moisture freeze/thaw state requires a significant allocation of energy, which results in a suppression of the magnitude of diurnal surface temperature changes. This leads to a change in the significance of sensible heat fluxes to the surface energy balance. The Variable Infiltration Capacity (VIC) macroscale hydrology model has been used to simulate the effects of seasonal soil frost on water and energy fluxes in the upper Mississippi River basin. Simulations were conducted using daily meteorological observations from 1950 through 1997. Comparisons of water and energy fluxes between model simulations with and without the frozen soil algorithm are used to evaluate the role of seasonal soil frost in the hydrologic cycle and identify seasonal conditions under which the response to frozen soil is more pronounced.