HR: 15:30h
AN: B23C-08    [Abstracts]
TI: Evidence for anoxic conditions in subglacial and proglacial environments
AU: * Wadham, J
EM: j.l.wadham@bris.ac.uk
AF: Bristol Glaciology Centre, School of Geographical Sciences, Bristol University, University road, Bristol, BS81SS United Kingdom
AU: Cooper, R
EM: r.cooper@macaulay.ac.uk
AF: The Macauley Institute, Craigiebuckler,, Aberdeen, AB15 8QH United Kingdom
AU: Tranter, M
EM: M.Tranter@bris.ac.uk
AF: Bristol Glaciology Centre, School of Geographical Sciences, Bristol University, University road, Bristol, BS81SS United Kingdom
AU: Bottrell, S
EM: simon@earth.leeds.ac.uk
AF: University of Leeds, School of Earth Sciences, University of Leeds,, Leeds, LS2 9JT United Kingdom
AU: Raiswell, R
EM: r.raiswell@earth.leeds.ac.uk
AF: University of Leeds, School of Earth Sciences, University of Leeds,, Leeds, LS2 9JT United Kingdom
AB: Glacial sediments may be host to a range of microbial communities, which drive oxic waters towards anoxia along hydrological flowpaths. Chemical and isotopic signatures in meltwaters from Finsterwalderbreen, a polythermal glacier on sedimentary bedrock in Svalbard, show clear evidence for anoxia at the glacier bed and in waterlogged proglacial sediments. Increases in „34S and „18O of sulphate in subglacial upwelling waters sampled in 1997 indicate the microbially-mediated reduction of sulphate. The „13C of the dissolved inorganic carbon is isotopically light \{„13C = -8 %\}, which is consistent with the use of bedrock kerogen and/or the necromass of sulphide oxidizing bacteria as organic substrates for the sulphate-reducing bacteria. Meltwaters sampled from the same outflow two years subsequently do not show evidence of sulphate reduction. Instead they are depleted in „34S and „18O of sulphate, suggesting that anoxic sulphide oxidation is a significant process and that subglacial flowpaths have become more oxygenated. Proglacial groundwaters are isotopically light with respect to „34S and „18O, demonstrating that anoxic sulphide oxidation is an important process here also. Variations in the isotopic composition of sulphate between years in the subglacial case and within a single summer in the proglacial case are linked to shifts in local hydrological conditions and drainage reorganisation.
DE: 1806 Chemistry of fresh water
DE: 1827 Glaciology (1863)
DE: 1040 Isotopic composition/chemistry
DE: 1045 Low-temperature geochemistry
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting