Melting Ice Sheets Release Tons Of Methane Into The Atmosphere, Study Finds

While some methane had been detected previously in Greenland ice cores and in an Antarctic Subglacial Lake, this is the first time that meltwaters produced in spring and summer in large ice sheet catchments have been reported to continuously flush out methane from the ice sheet bed to the atmosphere.

Lead author, Guillaume Lamarche-Gagnon, from Bristol’s School of Geographical Sciences, said: “What is also striking is the fact that we’ve found unequivocal evidence of a widespread subglacial microbial system. Whilst we knew that methane-producing microbes likely were important in subglacial environments, how important and widespread they truly were was debatable. Now we clearly see that active microorganisms, living under kilometres of ice, are not only surviving, but likely impacting other parts of the Earth system. This subglacial methane is essentially a biomarker for life in these isolated habitats.”

Most studies on Arctic methane sources focus on permafrost, because these frozen soils tend to hold large reserves of organic carbon that could be converted to methane when they thaw due to climate warming. This latest study shows that ice sheet beds, which hold large reserves of carbon, liquid water, microorganisms and very little oxygen – the ideal conditions for creating methane gas – are also atmospheric methane sources.

Co-researcher Dr Elizabeth Bagshaw from Cardiff University added: “The new sensor technologies that we used give us a window into this previously unseen part of the glacial environment. Continuous measurement of meltwater enables us to improve our understanding of how these fascinating systems work and how they impact the rest of the planet.”

With Antarctica holding the largest ice mass on the planet, researchers say their findings make a case for turning the spotlight to the south. Mr Lamarche-Gagnon added: “Several orders of magnitude more methane has been hypothesized to be capped beneath the Antarctic Ice Sheet than beneath Arctic ice-masses. Like we did in Greenland, it’s time to put more robust numbers on the theory.”

This study was a collaboration between Bristol University, Charles University (Czechia), the National Oceanography Centre in Southampton, Newcastle University, the University of Toronto (Canada), the Université Libre de Bruxelles (Belgium), Cardiff University (UK), and Kongsberg Maritime Contros (Germany). It was funded by the Natural Environment Research Council (NERC), with additional funds from the Leverhulme Trust, the Czech Science Foundation, the Natural Sciences and Engineering Research Council of Canada, and the Fond de Recherche Nature et Technologies du Québec (Canada).

Contacts and sources:Aliya Mughal
Bristol University

Citation: ‘Greenland melt drives continuous export of methane from the ice sheet bed’ by Guillaume Lamarche-Gagnon, Jemma L. Wadham, et al. Nature, Doi: 10.1038/s41586-018-0800-0