Hourly measurements of soil temperature and a surrogate index of soil water ion concentration were collected from the active layer at a site in the discontinuous permafrost zone in central Alaska during two thaw seasons. These data were contoured and presented as a time-depth temperature field. The zero degree isotherm on the contour plot represents the thawed-frozen interface. In this way, the thickness of the thawed zone on any day can be determined. The time-dependent thaw depth (Z) is related to the degree days of thaw accumulated since the onset of ground thaw (ADDT) by a modified version of the Stefan equation (Z = b root ADDT). The slope (b) of 1.21 and correlation coefficient of 0.98 are nearly identical for bath thaw seasons. The slope should be similar for sites characterized by boreal forest underlain by permafrost and possessing a thick organic mat. There are variations, however, in the instantaneous rate of thaw, which are reflected as deviations from the best-fit line. These deviations are apparently linked to infiltrating precipitation. Several events of this nature were examined. Downward percolation caused dilution of soil water ion concentration from the surface downwards, and soil temperatures were simultaneously observed to change rapidly.
