Radar investigations of melt pathways in a natural snowpack

Melt pathways in a natural seasonal snowpack were investigated using high frequency FMCW radar to examine the use of radar as a tool for investigating water flow through snow, and to develop preliminary estimates of the number of flow fingers present and the amount of meltwater that they transport. Our data show that the radar can be used to sense melt features at distances of approximately one metre within this snowpack. Old refrozen fingers and new wet fingers both generate visible radar returns. Excavation of channels within the snowpack verified that the radar signals were from flow fingering. By counting the number of channels observed in the radar images and using snow lysimeter measurements of outflow from the snowpack, we estimated that in the early stages of the main snow melt season, this snowpack contained approximately three channels/m2, and that the flow through each channel was approximately 0·4 mm of water/channel/hour.