SUBGLACIAL SILICATE WEATHERING CHARACTERIZED USING BOREHOLE AND OUTLET STREAM WATERS FROM WEST GREENLAND

Subglacial waters retrieved from boreholes are compared with those collected from the terminus of Isunguata Sermia, a land-terminating outlet glacier of the West Greenland Ice Sheet. Boreholes were drilled to bedrock at four sites over two years, comprising a 35-km transect, with ice depths varying from 90 to 820 m. Analyses of major and minor cations and anions demonstrate that silicate weathering is the dominant process at work beneath the Greenland Ice Sheet; biotite and feldspar dissolution are the most significant reactions. A relative enrichment in metals like zinc, copper, and zircon suggests that accessory minerals from gneissic bedrock are also important contributors of ions to the subglacial hydrologic system. These results suggest that subglacial silicate weathering is an important source of metals and nutrients to the glacier foreland and surface oceans over both seasonal and glacial-interglacial time scales, with the potential to impact primary productivity in both ecosystems.