Hydrochemistry of ice stream beds—evaporitic or microbial effects?

Skidmore, M. L.; Tranter, Martyn; Tulaczyk, S. M.; Lanoil, Brian

doi:10.1002/hyp.7580

Cited by 76 publications

(40 citation statements)

References 57 publications

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“…The depletion of till pore water at MIS and WIS indicates that a substantial fraction of water flowing in the basal water system there has been previously stored in till. This finding may have important implications for the search for life in subglacial lakes because till pore water in the Siple Coast region has a much higher solute concentration than subglacial meltwater derived by direct melting of basal ice [ Skidmore et al , ]. The rates of groundwater recharge in our model yield residence times of till pore water on the order of 1000–10,000 years, providing a long period of time for biogeochemical weathering to result in solute enrichment [ Skidmore et al , ; Wadham et al , ].…”

Section: Discussionmentioning

confidence: 92%

Significant groundwater contribution to Antarctic ice streams hydrologic budget

Christoffersen

Bougamont

Carter

et al. 2014

Geophys. Res. Lett.

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Satellite observations have revealed active hydrologic systems beneath Antarctic ice streams, but sources and sinks of water within these systems are uncertain. Here we use numerical simulations of ice streams to estimate the generation, flux, and budget of water beneath five ice streams on the Siple Coast. We estimate that 47% of the total hydrologic input (0.98 km 3 yr À1 ) to Whillans (WIS), Mercer (MIS), and Kamb (KIS) ice streams comes from the ice sheet interior and that only 8% forms by local basal melting. The remaining 45% comes from a groundwater reservoir, an overlooked source in which depletion significantly exceeds recharge. Of the total input to Bindschadler (BIS) and MacAyeal (MacIS) ice streams (0.56 km 3 yr À1), 72% comes from the interior, 19% from groundwater, and 9% from local melting. This contrasting hydrologic setting modulates the ice streams flow and has important implications for the search for life in subglacial lakes.

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Section: Discussionmentioning

confidence: 92%

Significant groundwater contribution to Antarctic ice streams hydrologic budget

Christoffersen

Bougamont

Carter

et al. 2014

Geophys. Res. Lett.

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“…Because silicate minerals contain trace amounts of nitrogen (e.g., in micas and feldspars) and potassium (in feldspars and biotite) [ Holloway and Dahlgren , 2002], their enhanced dissolution can supply subglacial environments with the nutrients required to sustain microbial life. The high concentrations (30 meq L −1 ) of *Na + and *K + in the KIS and BIS pore waters are consistent with enhanced silicate dissolution [ Skidmore et al , 2010] and suggest that chemical weathering beneath Antarctic Ice Streams is highly aggressive, driven by sulfide oxidation and microbially produced CO 2 . Consistent with these assertions is the morphology of sand grains sampled from the base of the Whillans Ice Stream (B), which are dominated by chemical weathering microfeatures similar to those visible on particles that have been crushed and treated with HF acid [ Tulaczyk et al , 1998].…”

Section: Wider Impacts Of Sub‐ice Sheet Chemical Weatheringmentioning

confidence: 93%

Biogeochemical weathering under ice: Size matters

Wadham

Tranter

Skidmore

et al. 2010

Global Biogeochemical Cycles

194

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[1] The basal regions of continental ice sheets are gaps in our current understanding of the Earth's biosphere and biogeochemical cycles. We draw on existing and new chemical data sets for subglacial meltwaters to provide the first comprehensive assessment of sub-ice sheet biogeochemical weathering. We show that size of the ice mass is a critical control on the balance of chemical weathering processes and that microbial activity is ubiquitous in driving dissolution. Carbonate dissolution fueled by sulfide oxidation and microbial CO 2 dominate beneath small valley glaciers. Prolonged meltwater residence times and greater isolation characteristic of ice sheets lead to the development of anoxia and enhanced silicate dissolution due to calcite saturation. We show that sub-ice sheet environments are highly geochemically reactive and should be considered in regional and global solute budgets. For example, calculated solute fluxes from Antarctica (72-130 t yr −1 ) are the same order of magnitude as those from some of the world's largest rivers and rates of chemical weathering (10-17 t km −2 yr −1 ) are high for the annual specific discharge (2.3-4.1 × 10 −3 m). Our model of chemical weathering dynamics provides important information on subglacial biodiversity and global biogeochemical cycles and may be used to design strategies for the first sampling of Antarctic Subglacial Lakes and other sub-ice sheet environments for the next decade.

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“…I and others now believe that the iron in subglacial runoff from Antarctic glaciers and icesheets is largely derived from sulphide oxidation, which appears to be the dominant biogeochemical reaction in the shallow sediments beneath the Antarctic Ice sheet (Raiswell et al, 2009;Skidmore et al, 2010;Wadham et al, 2010b). In Antarctica, as in other glacial environments, pyrite oxidation consumes oxygen and ultimately drives oxygen down to low, or zero, concentration levels producing anoxic conditions at the ice-rock interface (Brown et al, 1994;Raiswell et al, 2009;Wadham et al, 2012).…”

Section: Export Of Fe To the Southern Ocean By Subglacial Runoff And mentioning

confidence: 99%