Cryostratigraphic record of permafrost degradation and recovery following historic surface disturbances, Klondike area, Yukon

Cryostratigraphic investigation of near-surface permafrost at a site in the southern Klondike goldfields has revealed three ages of permafrost disturbance and recovery which potentially span the last century. In an undisturbed forest, the base of the modern active layer is stable with a suspended ice/sediment cryofacies at the contact. A recently burned site (2004) shows that the degrading contact has not yet stabilized. An earlier disturbance from the 1970s shows evidence of aggradation (upward shift) of the permafrost table following limited vegetation succession. Underlying all three sites is an older disturbance corresponding to a thaw depth of ~2 m, predating the 1970s disturbance; it is likely that this represents an early 20th century disturbance associated with the deforestation of the valley during the gold rush era. Permafrost has recovered significantly since that time as the boreal forest and understory vegetation was re-established, underscoring the role of vegetation cover in permafrost disturbance and recovery.