Award: OPP-1023233

The Greenland Ice Sheet is the largest freshwater reservoir in the northern hemisphere and its marginal ablation zones are degrading at an accelerated rate. Microbial metabolism in aquatic and sedimentary regions beneath the ice sheet will affect the composition of glacial outflow, possibly representing important sources of bioavailable micronutrients (e.g. reactive Fe) for nearby water masses as well as atmospheric greenhouse gases (e.g. CH4). We found that subglacial water discharged from the western margin of the Greenland Ice Sheet contained significant concentrations of dissolved methane (2.7 to 83 μM). Further, the most abundant microorganisms inhabiting this subglacial microbial community were bacteria that have the capacity to use methane as a carbon and energy source. These results suggest that microbial communities poised in oxygenated subglacial drainage channels at the margin of ice sheets could serve as significant methane sinks. The methane present in the outflows could be from contemporary microbial processes or may have been released from thawing sediments that stored methane previously. In the latter scenario, there is potential for the release of large amounts of methane with greater thawing. The education and outreach theme of this projected have revolved around a central question: what lives and happens under the ice sheets? Exploring subglacial environments as a æfinal frontierÆ in the study of life in the subsurface biosphere is highly relevant given the need for collection of baseline data on subglacial conditions proximal to the ice sheet margin. Last Modified: 11/20/2015 Submitted by: Brent C Christner