Award: OPP-1023462

In this project we studied the influence that that Greenland Ice Sheet (GrIS) has on the microbiology and chemistry underneath the ice. Our study focused on the sub-ice sheet environment which is not well known to characterize the microbial communities and the chemical processes, as well as the interactions between them. The GrIS is the largest freshwater reservoir in the northern hemisphere and is experiencing rapid changes including unprecedented melting in historical times. Our working hypothesis is that microbial communities exist below the ice sheet and they affect the weathering of the rock. Our study sites are located in the Thule and Kangerlussuaq areas along the west coast of Greenland and include two major rock types, sedimentary and crystalline rock. We monitored water flowing along the side of, on top of, and coming from underneath the ice sheet for one season at each location. We also investigated fresh snow on top of the ice sheet and basal ice at the base of GrIS. Our primary finding include identifying a diverse assemblage of bacteria on top of the ice sheet that are characteristic of the adjacent soils in the ice-free areas. On the other hand, the snow chemical signatures was more similar to a marine signature. These finding suggest the snow chemistry is determined when the snow fall and traps marine aerosols, while the snow bacteria are dominated by soils likely due to dust input from the relative dry, barren adjacent areas. The Thule glacial meltwater microbial sequence analysis indicated a diverse bacterial community that was comparable to seeding environments such as snow, soil, moraines and meltwater on the glacier. The iron chemistry of the waters was more similar to that of soil. This is consistent with our observation that the Thule drainages are dominated by the local periglacial environment. At Kangerlussuaq we monitored a drainage that emerged from under the ice cap. These waters revealed an active microbial community with methane being present in the water indicating oxygen as being consumed. The microbial assemblage was dominated by bacteria that are able to use methane as a carbon source. In addition, methane producing bacteria DNA was detected. While the ultimate source of the carbon remains to be determined (i.e. carbon in the ice or in the underlying sediments), this is the best documentation of an active microbial community under the GrIS that potentially may contribute to greenhouse gases. The effect of recent melting of the GrIS remains to be determined. Our studies also indicate a substantial flux of bioavailable iron is be released to the adjacent oceans. Iron is often the limiting nutrient in the ocean so this maybe have substantial effects on the marine ecosystems. Our studies also modeled the weathering of rocks under the glacier using a technique known as inverse modeling. In this type of modeling we determine the rocks that may have weathered by analyzing water chemistry coming from under the glacier as well as the input water coming into the glacier. This type of study helps us estimate the amount of rocks weathering and is important for understanding long-term carbon cycles. In summary, the outcomes of this projects are as follows. Methane is present in subglacial waters along with a dominance of methane-consuming bacteria. Methanotrophic (methane-producing) bacteria were also found to be viable members of the subglacial ecosystem. While based on the isotopic chemical signature, we are confident that the source of methane is biological, although we do not know if it is being produced currently or being released from thawing sediments. The concentration of the form of iron that can act as a fertilizer to oceans is much higher in the subglacial drainage versus rivers draining the ice-free areas. We were able to develop sensible chemical models of the rocks that are weathering under the ice sheet along with mediating microbial reactions thereby allowing us to better understa...