The coupling between hydrology, the development of the active layer and the chemical signature of surface water in a periglacial catchment in West Greenland

Abstract. The chemical signature of surface waters is influenced by the interactions with soil particles and old groundwater. In permafrost landscapes ground ice restricts the flow of water in soils, and this implies a limited influence of, e.g., weathering on the chemical signature of the runoff. The aim of this study was to test to what extent freeze-thaw processes, hydrology and water-age play for shaping the chemical and isotopic signature of surface water and shallow groundwater in a catchment in West Greenland. Measuring runoff in remote catchments is challenging, and we therefore use a validated hydrological model to estimate the daily runoff over multiple years. We have also used a particle tracking simulation to determine the age of groundwater, and isotopic and chemical data from various water types (surface water, groundwater, lake water and precipitation) collected during different hydrological situations. Together this shows that even though the age of the groundwater rarely exceeds 4 years, runoff is dominated by subsurface flow, and overland flow is restricted to the early snowmelt period and heavy rain events. Our monitoring of the active layer indicates a rapid thaw, especially in connection with running water, and melting of ground ice quickly becomes an important fraction of the runoff. Taken together our data indicate that, similar to in other climatic settings and despite the lack of truly old groundwater and a shallow active layer, there is a profound influence from soil processes on the chemical and isotopic signature of the runoff.