Land surface insulation response to snow depth variability

The existing literature on heat diffusion through a snow-covered land surface deals primarily with snow cover presence or duration; however, the insulation property of a snowpack can vary substantially owing to the changes in snow thickness. Using SNTHERM, a one-dimensional snowpack energy and mass balance model, we have isolated the heat diffusion response to varying initial snow depths, including snow-free conditions, and assessed the magnitude of associated temperature and insulative energy flux anomalies within the entire snowpack-soil column system. A clear and substantial land surface insulative response to snow depth is identified over hourly, intraseasonal, and interannual time scales. The overall snow-soil system warms with increasing snow depth, but the surface snow layer cools slightly, generating decreased ground heat flux and increased sensible heat flux responses. This land surface thermal response is attributable to the increased insulative capacity of deeper snowpacks, which makes the underlying soil less responsive to solar radiation and air temperature fluctuations, and facilitates sustained warming by the bottom soil layer boundary. Furthermore, the overall effect of increasing snow depth due to insulation is comparable in magnitude to the effect of snow presence versus snow absence due to albedo.