Abstract. In recent years, the analysis of firn in Greenland, Svalbard, and other high Arctic regions has contributed to the understanding of meltwater retention in firn and its importance to measurements of glacier mass balance. This has provided insight into firn densification processes and meltwater retention. Changes in these attributes can also provide insight into meteorological variability and climate trends. In spring 2018, two firn cores (21 m and 36 m in length) were extracted from the accumulation zone of Kaskawulsh Glacier, St. Elias Mountains, Yukon. The cores were analyzed for ice layer stratigraphy, density, and glaciochemical time series (oxygen isotopes and major ions). Meltwater percolation and refreezing events were evident in the cores. The quantity of ice layers, the presence of liquid water at 34.5 m depth, interpreted as a perennial firn aquifer (PFA), and the altered isotopic and glaciochemical signature all indicate this process. This melt resulted in an estimated surface lowering of 10 ± 0.8 cm/yr between 2005 and 2018. The information gleaned from Kaskawulsh Glacier supports the need for improved and field-validated density assumptions for geodetic mass balance methods.