Impacts of snow cover on the pattern and velocity of air flow in air convection embankments of sub-Arctic regions

In northern regions, air convection embankment (ACE) has been implemented to mitigate road subsidence caused by permafrost degradation. The seasonal snow cover largely alters the surface energy balance and adversely affects the thermal stability of the road. However, thermal characteristics of a closed ACE and the quantification of their impacts on talik development remain largely unknown, especially in the present and future context of global warming. Here, impacts of snow cover on the pattern and strength of the air circulation were investigated and quantified. Snow cover greatly weakened the cooling effect of the closed ACE side slopes. The pore air velocity of the crushed-rock layer was reduced by half and the mean annual heat flux increased by approximately 1.6 W/m(2), in comparison to the snow-free case. Conversely, the U-shape closed ACE had a better cooling performance due to a stronger air convection in winter, which increased heat loss from the snow-free surface of the embankment center. Our simulations suggest that the U-shape ACE embankment is a potential long-term solution to mitigate permafrost thaw over the life service (50 years) of road embankments in sub-arctic regions. The net results of this study are imperative to improve engineered design and road maintenance in cold regions.