Estimating soil thaw energy in sub-Alpine tundra at the hillslope scale, Wolf Creek, Yukon Territory, Canada

Accurate representations of subsurface flow in hydrologic models of permafrost terrain during spring thaw require an understanding of soil thaw and soil thaw rates. Field data, including daily photographs for snowcover estimation and meteorological measurements, and measurements of soil thaw depth, soil temperature and soil moisture content, were acquired on an organic-covered hillslope in Granger Basin, Yukon Territory, to quantify relationships between net radiation and soil thaw energy. The infiltration and freezing of meltwater into the soil likely contributes to pre-thaw warming. When this energy (1.82 MJ m⁻² d⁻¹) is taken into consideration, the daily mean contribution to soil thaw from net radiation is approximately 9%. Accounting for a period of refreezing that occurred during the study period and distributing the energy across the hillslope, the measured and estimated soil thaw depths compared well (R²=0.92 and slope = 1.09). This research contributes to the understanding of active layer development, sheds insight into the role of infiltrating and freezing meltwater on soil thaw and provides an approach for the estimation of soil thaw based on a direct link between surface net radiation and the subsurface energy regime.