Hydrochemistry of hillslope permafrost catchments with degrading and stable ice-wedge polygons, Ogilvie Mountains, Yukon, Canada

Ice-wedge polygonal terrain is one of the most widespread landscapes in continuous permafrost, and at many locations, is undergoing substantial degradation. Set in central Yukon, this study investigates the hydrochemistry of two hillslope subcatchments, one with degrading and one with stable ice-wedge polygons. Ice-wedge degradation began in the 1990s with the formation of a pond. In summer of 2022 and 2023, episodes of filling and drainage of the pond were observed. The geochemical analyses show that the contribution of wedge-ice meltwater is barely detectable in the trough and thaw pond. Results suggest that the water track and pond are mainly fed by snowmelt in early summer but are recharged by rainfall in mid-to-late summer. Further, as the active layer progressively thaws in summer, there is an increased contribution of ions to the surface waters from the dissolution of carbonates by soil water. However, the stream in the catchment with stable polygons has a much higher solute load. This suggests that unlike other types of permafrost degradation, the degradation of ice-wedge polygons may not necessarily have adverse effect on water quality in a catchment.