depth_at_base_of_unfrozen_ground

The phrase depth_at_base_of_unfrozen_ground is the instantaneous depth of the downward penetration of thaw from the ground surface at a given time. Permafrost is soil or rock that has remained at a temperature at or below zero degrees Celsius throughout the seasonal cycle for two or more consecutive years. The maximum measurable depth_at_base_of_unfrozen_ground value as recorded at the end of a thawing season corresponds to the permafrost_active_layer_thickness. rdf:langString