Glacier Biogeochemistry

Our group has been involved since 1989 in the development of the field of glacier biogeochemistry. Our initial studies of melt water chemistry with Martyn Tranter and Giles Brown (Bristol) were important in characterizing the range of important subglacial weathering processes and showing how meltwater chemistry could help us better understand the workings of subglacial drainage systems. This work also revealed that a range of redox reactions that are often microbially mediated seemed to be occurring subglacially and set us off on the search for life in and under glacier ice. Work with John Parkes (Cardiff) and Ian Fairchild (Birmingham) showed that microbial populations were present, and surprisingly abundant, in both subglacial waters and sediment-rich basal ice. With Mark Skidmore (now at Montana State) and Julia Foght (Uof A Biological Sciences), we showed that these microbes were viable under near in-situ conditions and that they included sulphate and nitrate reducers and methanogens. This led us to propose the hypothesis that Quaternary ice sheets of the northern hemisphere, which may have overrun large pools of organic carbon during their growth, may have served as giant composters, and that subglacial production of CO2 and methane may have been globally significant geochemical processes.

In subsequent work with Brian Lanoil (UC Riverside), we were able to show that the composition of subglacial microbial communities appeared to vary in a way that was consistent with the dominant weathering processes indicated by melt water chemistry. This provides further evidence that these communities are active subglacially. More recently, Maya Bhatia was able to show that while subglacial communities contain elements of communities found in supraglacial snow and proglacial soils and sediments, most of the organisms in the subglacial populations are unique to that environment. This again suggests the existence of active microbial communities that are adapted to the specific environmental conditions associated with glacier beds – low light availability, low but stable temperatures, and generally low availability of nutrients and potential energy sources.

Melissa Lafreniere (now at Queen’s) initiated the study of organic matter in glacial systems with a study at Bow Glacier, where she found that most of the dissolved organic carbon (DOC) in glacial melt water was microbial in character. Joel Barker (Now at Byrd Polar Research Institute, Ohio State) extended this work to other systems in the Arctic, Antarctic and Northern British Columbia. His work (in collaboration with Ray Turner (Calgary) and Sean Fitzsimon (Otago)) confirms that much of the DOC and particulate organic carbon (POC) in glacial systems is microbial in origin. In some cases, however, humic matter is removed from the glacier in runoff, and changes in the balance between microbial and humic OC can provide insights into the function of the subglacial drainage system similar to those derived from inorganic melt water chemistry.
We have also been active in the study of the behaviour of pollutants in glacial systems. With David Schindler (UofA Biological Sciences) and Jules Blais (Ottawa) we studied the inputs of persistent organic pollutants (POPs) to Bow Lake, Alberta. We found that most of the input occurs in glacial runoff and that this was largely due to the lack of organic carbon in glacial catchments (which limited the removal of POPs from solution and retention on catchment soils and vegetation) and the way in which melt water is routed through glaciers (channelisation of flow within the glacier limits the degree of contact between water and soils and vegetation in the proglacial area). With Vince St Louis (U.Alberta Biological Sciences) and his students, we have been working on the behaviour or mercury in Arctic and Antarctic systems. Key findings of this work have been that mercury deposited to snowpacks during atmospheric mercury depletion events is rapidly returned to the atmosphere, so that net deposition of mercury to arctic ecosystems is quite low, and that a surprisingly high fraction of the mercury in the snow is in the toxic methylated form. The distribution of methyl mercury seems to be correlated with the amount of chloride in the snow, suggesting a marine source for this species.

Ongoing biogeochemical work (with Sean Fitzsimons (Otago) and Denis Samyn (Brussels) is focused largely in the McMurdo Sound region of Antarctica, where we are interested in the biogeochemistry of basal ice, the role of hydrological interactions between glaciers and permanently ice covered proglacial lakes in providing a nutrient and carbon source for subglacial microbial populations, and biogeochemical processes (including nutrient cycling) in melt ponds on the McMurdo Ice Shelf. We will also be involved in a new project (funded by NERC, UK) led by Jemma Wadham (Bristol) on microbial methane production under ice sheets and glaciers.

Ashley Dubnick (in collaboration with Joel Barker and Jemma Wadham) analyzed ice and water from seven polar glacier systems in the Canadian Arctic, Norwegian Arctic and Antarctica to determine their supraglacial, englacial, subglacial and/or proglacial DOC characteristics. A model of the fluorescent DOC revealed the presence of predominantly proteinaceous DOC. The study also found that the DOC of the seven glacier systems display broadly similar fluorescent characteristics indicating a significant degree of DOC consistency regardless of geographically distinct locations, specific glacier thermal regimes and differing organic matter sources. Differences in DOC characteristics were, however, apparent between the supraglacial, englacial, subglacial and proglacial environments of a glacier system suggesting that either the sources of organic matter or the biogeochemical processes affecting DOC characteristics are different between these environments.