Detection of Frozen and Unfrozen Interfaces with Ground Penetrating Radar in the Nearshore Zone of the Mackenzie Delta, Canada

Multi-frequency Ground Penetrating Radar (GPR) surveys were conducted within the nearshore zone of the Mackenzie Delta to determine the spatial distribution of frozen and unfrozen sediment. Late winter GPR surveys over zones of bottom-fast and floating ice indicate that significant spatial variations in the thermal state of sediments exist. Where ice was bottom-fast, two laterally-continuous high amplitude reflections were verified to represent a transition in thermal state of sediment. These thermally-related interfaces closely correlate with changes in ground temperatures from above freezing to below-0.5oC. At locations where bottom-fast ice thickness was less than 1 m complete freezeback of the active layer occurred. Where bottom-fast ice thickness was greater than 1 m thaw exceeded freezeback of the active layer and a near-surface talik was identified. The depth of seasonal frost decreased towards zones of floating ice, beneath which no near-surface thermal interfaces were resolved