Abstract
Abstract. Over 11 000 L of kerosene was deposited on the surface of Rabots glaciär on the Kebnekaise Massif, northern Sweden, following the crash of a Royal Norwegian Air Force aircraft in March 2012. An environmental monitoring programme was subsequently commissioned, including a series of dye tracing experiments during the 2013 melt season, conducted to investigate the transport of pollutants through the glacier hydrological system. This experimental set-up provided a basis from which we could gain new insight into the internal hydrological system of Rabots glaciär. Results of dye tracing experiments reveal a degree of homogeneity in the topology of the drainage system throughout July and August, with an increase in efficiency as the season progresses, as reflected by decreasing temporary storage and dispersivity. Early onset of melting likely led to formation of an efficient, discrete drainage system early in the melt season, subject to decreasing sinuosity and braiding as the season progressed. Four distinct meltwater flow regimes are identified to summarize the temporal and spatial evolution of the system. Analysis of turbidity-discharge hysteresis further supports the formation of discrete, efficient drainage, with clockwise diurnal hysteresis suggesting easy mobilization of readily available sediments in channels. Dye injection immediately downstream of the pollution source zone reveals prolonged storage of dye followed by fast, efficient release. Twinned with a low dye recovery, and supported by sporadic detection of hydrocarbons in the proglacial river, we suggest that meltwater, and thus pollutants in solution, may be released periodically through an efficient, and likely pressurized, hydrological system within the upper reaches of the glacier.
Highlights
Dye tracing provides an opportunity to study the otherwise unseen drainage system inside and underneath glaciers
As throughflow velocities experienced no increase with time, we propose that the reduction in storage retardation over time relates to increasing efficiency, and decreasing sinuosity, rather than evolution from a true distributed system to a channelized system, which had likely already formed due to early onset of melting in 2013
The results of dye tracing experiments provide a first look into the internal hydrological system of Rabots glaciär, offering a new insight into both the properties and transit times of meltwater flow through the glacier
Summary
Dye tracing provides an opportunity to study the otherwise unseen drainage system inside and underneath glaciers. Nienow et al, 1998; Willis et al, 2009; Cowton et al, 2013). Dye tracing has been applied successfully in the alpine environment in several studies and has contributed substantially to understanding of subglacial drainage systems, for example, Storglaciären in the Kebnekaise mountains in northern Sweden The number of extensive dye tracer studies of glaciers is still limited (Willis et al, 2012), and basic unresolved issues remain in understanding the temporal and spatial variability of glacial drainage systems, the extent of efficient drainage, and the morphology of englacial and subglacial drainage. Of the initial 14 100 L of kerosene jet fuel on board at take-off, an estimated minimum of 11 100 L was sprayed over the snow and ice-covered mountain environment, together with 50 L of hydraulic oil and 170 L of turbo
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