An investigation of the abundance and molecular characteristics of organic matter in glacier systems

Reports of viable microbial populations in basal ice and subglacial meltwater, and evidence of subglacial microbial metabolism, challenges the conceptual model of an abiotic subglacial environment. Glaciers overrun organic matter (OM) during advance, and supraglacially-derived OM is routed subglacially through moulins and crevasses in supraglacial meltwater. Subglacial OM may support heterotrophic microbial metabolism. Heterotrophy affects the abundance and molecular characteristics of OM exported to downstream environments in glacier meltwater and OM abundance and characteristics affects aquatic ecology. Glaciers are water sources to rivers globally. Increased glacier melt in response to climate warming will increase OM export from glaciers to downstream ecosystems. Given the importance of OM abundance and characteristics to downstream aquatic ecology, an understanding of the abundance and behaviour of OM in glacier systems is important. Few studies have addressed the topic of OM export from glaciers, and a direct assessment of OM abundance and characteristics in glacier systems is lacking. The purpose of this thesis is to quantify OM abundance in a range of glacier environments, characterize OM that is stored within and exported from glacier systems and determine the factors that influence the OM flux to downstream environments. To address these objectives, the abundance, fluorescence and infrared absorption characteristics of OM in glacier meltwater and ice were investigated at John Evans Glacier and Outre Glacier, Canada, and Victoria Upper Glacier, Antarctica.; Dissolved organic carbon was detected in all of these glaciers (0.06--46.6 ppm). The fluorescence characteristics of dissolved organic carbon in meltwater and ice indicates that several organic pools exist subglacially which are of microbial and terrestrial provenance. OM mobilization from these pools is influenced by subglacial meltwater flow routing. The infrared characteristics of particulate organic carbon in basal ice indicates that there is a microbial component to OM in basal ice regardless of potential source OM.; The export of microbially-derived OM to downstream ecosystems represents the export of labile OM from glacier systems. This export may contribute to a positive feedback with climate warming as an increased OM flux in meltwater increases heterotrophy in glacially-fed rivers and increases the flux of CO 2 to the atmosphere.