| Hydrochemical analysis of waters draining polythermal John Evans Glacier, Ellesmere Island, during the summer of 2000 indicated significant chemical weathering of gypsum, calcite, dolomite and feldspars within the subglacial environment. Geochemical modeling using data collected in the field indicated that the balance of weathering rates was different in different hydrological settings. Calcite and gypsum dissolution were important m high discharge waters, and dolomite and feldspar dissolution were important in low discharge waters. A two-component drainage system was thus implied. At high discharge, the subglacial drainage system is at high pressure, and SSC is high. At low discharge, a drop in water pressure in subglacial channels allows stored water from the surrounding distributed system to enter the channels and exit the subglacial environment. This degree of subglacial channel development on an Arctic glacier is unusual, and is attributed to an unusually high rate of meltwater input to the subglacial environment. |
