Pathways and Transit Time of Meltwater in the Englacial Drainage System of Rabots Glacier, Kebnekaise, Sweden

Abstract: Following the crash of a Norwegian Hercules aircraft on Rabots glaciär in the Kebnekaise mountain range in 2012, a field campaign was initiated in order to assess the fate of the hydrocarbon pollution in the system. It is hypothesized that soluble components of the aircraft fuel will be transported within the glacial meltwater. This thesis focuses on constraining the likely transit time and dispersion of the meltwater as a proxy for potential pollution pathways. Therefore, the hydrologic configuration of Rabots glaciär was studied during the ablation season 2013 by means of dye tracing experiments and discharge monitoring in the proglacial stream. The analyses of the dye return curves and stream monitoring suggest that Rabots glaciär exhibits a widely efficient drainage system towards the end of the ablation season, but with analyses revealing heterogeneity in the drainage system form. The seasonal evolution of efficiency was also assessed, showing an increase over time, although was hampered by early onset of melting before the field season began. There are different hydrological configurations on the north and south side of the glacier, possibly influenced by shading. The system on the north side is routing meltwater along the glacier bed over a long distance as indicated by the turbid outlet stream. Water routing on the southern side likely occurs through englacial channels. This configuration may be influenced by the thermal regime and distribution of cold surface layers. It has further been revealed that both systems are likely to be disconnected from each other. Pollution that is transported with the meltwater down from the crash site on the southern side does not reach the drainage system on the northern side. Besides revealing potential pathways for soluble hydrocarbon pollutants, this case study contributes to the previously very limited knowledge of Rabots glacial hydrology, and our general understanding of polythermal glacier hydrology.