THE HYDROCHEMISTRY OF A RETREATING ARCTIC GLACIER AND ITS PROGLACIAL ZONE

Retreating arctic glaciers and their forelands are sites of intense biogeochemical activity strongly coupled to the specific hydrology of this environment. The resulting chemical weathering might contribute to the global cycling of carbon and other elements but the related material fluxes are not thoroughly known because relatively few glaciers have been studied from this viewpoint.

Werenskiold Glacier is a high arctic valley glacier on SW Spitsbergen (Svalbard, Norway). Its subglacial runoff is concentrated in two outflows located at glacier terminus. Physico-chemical properties (pH, alkalinity, electric conductivity, selected major and minor ions, δ¹⁸O and δD of water) of subglacial outflows were investigated at different stages of glacier-melt period. The observed hydrochemical variations seem to primarily reflect changing contributions of the oxic and anoxic biogochemical processes to solute release. The subglacial runoff is carried to the nearby Greenland Sea by streams which interact hydrologically with the active layer of the proglacial zone. Contributions from the subsurface drainage as well as the hyporheic exchange transform stream water causing longitudinal trends in its solute content and stable isotope composition. Measurements made with piezometers showed that due to conditions favourable for sulphide oxidation the active layer water is enriched with solutes in comparison to surface water and supersaturated with CO₂ in comparison to the atmosphere. Release of CO₂ from the active layer might counterbalance consumption of atmospheric CO₂ associated with subglacial carbonate dissolution and with replenishment of proglacial streams with this gas. Reliable estimation of these carbon fluxes requires a comprehensive mathematical model that would integrate the biogeochemical and hydrogeological processes in the glacial and proglacial environments. Coupling between these processes is, however, not straightforward. Results of this study show, for example, that water properties of the active layer reveal complex and variable spatial patterns.

This study was financed by the Polish Ministry of Science and Higher Education from the budgetary funds in years 2007-2009 (26/IPY/2007/01).