THE HYDROCHEMISTRY OF RUNOFF FROM A COLD-BASED GLACIER IN THE HIGH ARTIC (SCOTT TURNERBREEN, SVALBARD)

There are still relatively few hydrochemical studies of glacial runoff and meltwater routing from the high latitudes, where non-temperate gl acier ice is frequently encountered. Representative samples of glacier meltwater were obtained from Scott Turnerbreen, a 'cold-based' glacie r at 78 degrees N in the Norwegian high Arctic archipelago of Svalbard , during the 1993 melt season and analysed for major ion chemistry. La boratory dissolution experiments were also conducted, using suspended sediment from the runoff. Significant concentrations of crustal weathe ring derived SO42- are present in the runoff, which is characterized b y high ratios of SO42-: (SO42- + HCO3-) and high p(CO2). Meltwater is not routed subglacially, but flows to the glacier terminus through sub aerial, ice marginal channels, and partly flows through a proglacial i cing, containing highly concentrated interstitial waters, immediately afront the terminus. The hydrochemistry of the runoff is controlled by : (1) seasonal variations in the input of solutes from snow- and iceme lt; (2) proglacial solute acquisition from the icing; and (3) subaeria l chemical weathering within saturated, ice-cored lateral moraine adjo ining drainage channels at the glacier margins, sediment and concentra ted pore water from which is entrained by flowing meltwater. Diurnal v ariations in solute concentration arise from the net effects of variab le sediment pore water entrainment and dilution in the ice marginal st reams. Explanation of the hydrochemistry of Scott Turnerbreen requires only one major subaerial flow path, the ice marginal channel system, in which seasonally varying inputs of concentrated snowmelt and dilute icemelt are modified by seepage or entrainment of concentrated pore w aters from sediment in lateral moraine, and by concentrated interstiti al waters from the proglacial icing, supplied by leaching, slow draina ge at grain intersections or simple melting of the icing itself. The i ce marginal channels are analogous neither to dilute supra/englacial n or to concentrated subglacial flow components. (C) 1998 John Wiley Son s, Ltd.