Potential methane reservoirs beneath Antarctica

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Abstract

Once thought to be devoid of life, the ice-covered parts of Antarctica are now known to be a reservoir of metabolically active microbial cells and organic carbon1. The potential for methanogenic archaea to support the degradation of organic carbon to methane beneath the ice, however, has not yet been evaluated. Large sedimentary basins containing marine sequences up to 14 kilometres thick2 and an estimated 21,000 petagrams (1 Pg equals 1015 g) of organic carbon are buried beneath the Antarctic Ice Sheet. No data exist for rates of methanogenesis in sub-Antarctic marine sediments. Here we present experimental data from other subglacial environments that demonstrate the potential for overridden organic matter beneath glacial systems to produce methane. We also numerically simulate the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model3 and show that pressure/temperature conditions favour methane hydrate formation down to sediment depths of about 300 metres in West Antarctica and 700 metres in East Antarctica. Our results demonstrate the potential for methane hydrate accumulation in Antarctic sedimentary basins, where the total inventory depends on rates of organic carbon degradation and conditions at the ice-sheet bed. We calculate that the sub-Antarctic hydrate inventory could be of the same order of magnitude as that of recent estimates made for Arctic permafrost. Our findings suggest that the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage.

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Figure 1: Methane production in sub-Antarctic sediments.
Figure 2: Methane hydrate+gas accumulation potential beneath the ice sheet.
Figure 3: Vertical profiles of methane solubility, dissolved methane, methane hydrate and methane gas in zero flux simulations.
Figure 4: Modelled thermogenic methane accumulation beneath WAIS over 1 Myr of glaciation under the maximum flux scenario ( v = 0.1, TOC(0,0) = 1%).

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Acknowledgements

This research was funded by the Natural Environment Research Council (UK—NERC grant NE/E004016/1) and the National Science Foundation WISSARD project (NSF-AISS 0839142). Support to J.L.W. was also provided by the Leverhulme Trust via a Phillip Leverhulme award and to S.A. by the Netherlands Organisation for Scientific Research (NWO). We acknowledge NSERC and Antarctica New Zealand for financial and logistic support for sampling in Antarctica and the Polar Continental Shelf Project for financial and logistic support for sampling in Arctic Canada. We thank S. Fitzsimons for assistance with sampling in Antarctica. A.D. was funded by an NSERC Undergraduate Student Research Award. This research used data provided by the Ocean Drilling Program. The Ocean Drilling Program is sponsored by the US National Science Foundation and participating countries under the management of the Joint Oceanographic Institutions, Inc. We thank C. Ruppel for comments on this manuscript.

Author information

J.L.W. wrote the paper and directed the work, and led the sample collection in Greenland. S.A. did the numerical modelling and contributed to manuscript preparation. S.T. assisted with the modelling and contributed to manuscript preparation. M.S. contributed to the writing of the manuscript and did experimental work. J.T. did the initial design of incubation experiments, laboratory analysis of incubation experiments, and sample collection. G.P.L. performed laboratory analysis of the incubation experiments, and did sample collection. E.L. performed laboratory analysis of incubation experiments. A.D. performed laboratory analysis of the incubation experiments. M.T. assisted with the manuscript and modelling calculations. M.J.S. added input to the incubation experiments, and did sample collection of Antarctic subglacial material. A.M.A. assisted with writing the manuscript and advised upon incubation experiments. A.R. assisted with manuscript preparation and numerical modelling. C.B. assisted with the laboratory analysis of the incubation experiments.

Correspondence to J. L. Wadham.

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Wadham, J., Arndt, S., Tulaczyk, S. et al. Potential methane reservoirs beneath Antarctica. Nature 488, 633–637 (2012) doi:10.1038/nature11374

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