Volcanoes and glaciers combine to become powerful producers of methane

Scientists have discovered that large quantities of methane, a powerful greenhouse gas, are being released by an Icelandic glacier.

A study of the Sólheimajökull glacier, which comes from the active Katla volcano and covered with ice, shows that up to 41 tons of methane are released by the meltwaters every day during the summer months. This is roughly equivalent to the methane produced by more than 136,000 belching cows.

The research conducted by Lancaster University, which appears in Scientific reports, is the first published field study showing methane releases from glaciers at this scale.

"There is a tremendous amount of methane lost in the flux of glacial melt in the atmosphere," said Dr. Peter Wynn, Glacial Biogeochemist at the Center. Lancaster environment and corresponding author of the study. "It largely exceeds the average losses of methane in the atmosphere by non-glacial rivers reported in the scientific literature, and competes with some of the world's most methane-producing wetlands, accounting for more than 20 methane known to all the other volcanoes in Europe put together. "

Dr. Wynn added, "Methane has a global warming potential 28 times higher than carbon dioxide (CO2), so it is important to know the different sources of methane released to the atmosphere and to determine how they might be affected. change in the future.

"There has been a lot of speculation that glaciers may or may not release methane.The glacier beds contain the perfect cocktail of conditions conducive to the production of methane – microbes, lack of oxygen, organic matter and water – as well as a waterproof ice cap on the surface of the water surface trapping the methane below.

"However, no one has done extensive research on this in the field and this is the greatest proof to date that glaciers release methane."

The PhD study Dr. Rebecca Burns, a graduate researcher at Lancaster University, conducted research at the Center for Global Eco-innovation, funded in part by the European Regional Development Fund.

Mr. Burns collected water samples from the meltwater lake in front of the Sólheimajökull glacier and measured methane concentrations, comparing them to the methane levels in the sediments and other surrounding rivers, in order to ensure that methane would not be released by the surrounding landscape.

"The highest concentrations have been found at the point where the river flows under the glacier and into the lake, which shows that the methane must come from the subglacier," says Dr. Wynn.

With the aid of a mass spectrometer, which identifies the unique "fingerprint" of methane, researchers discovered that methane came from a microbiological activity at the glacier bed. But there is always a connection with the volcano.

"We believe that even if the volcano does not produce methane, it provides the conditions that allow microbes to grow and release methane into the surrounding meltwater," said Dr. Wynn.

Normally, when methane comes in contact with oxygen, it combines to form CO2, so that methane actually disappears. On a glacier, melts rich in dissolved oxygen reach the bed of the ice mass and convert the methane present into carbon dioxide.

"Understanding the seasonal evolution of the subglacial drainage system of Sólheimajökull and its interaction with the Katla geothermal area was part of this work," said Professor Fiona Tweed, an expert in glacial hydrology at Staffordshire University and co-ordinator. – author of the study.

In Sólheimajökull, when the meltwater reaches the glacier bed, it comes into contact with the gases produced by the Katla volcano. These gases reduce the oxygen content of the water, which means that some of the methane produced by microbes can be dissolved in water and transported out of the glacier without being converted to CO2.

Dr. Hugh Tuffen, a volcanologist at Lancaster University and co-author of the study, said, "The heat of the Katla volcano could dramatically accelerate the generation of microbial methane, so you might consider Katla a giant microbial incubator.

"Scientists have recently discovered that Katla emits large amounts of CO2 – it is among the world's top 5 in terms of CO2 emissions from volcanoes, so Katla is certainly a very interesting and very gassy volcano."

"Iceland and Antarctica have many active volcanoes covered with ice and geothermal systems," said Dr. Burns. The recent report of the International Panel of Experts on Climate Change (IPCC) highlights that current trajectories indicate that global warming is expected to reach 1.5 ° C between 2030 and 2052, with the greatest sensitivity at higher latitudes, if the methane produced under these icecaps escaping as the ice is diluted, we may experience a short-term increase in methane release from ice masses in the future . "

Andri Stefansson, professor of hydrothermal geochemistry at the University of Iceland, who did not participate in the study, said: "These results provide important and new information on the subject. origin and fluxes of methane on the Earth's surface and on the importance of this greenhouse gas to the environment, atmosphere of these systems.

However, the researchers warned that it was not yet clear how these effects would manifest themselves. They think that even if a peak of methane could be released in the short term as the glacier melts and thins, the process could self-limit in the long run as, for other reasons without ice, the methane production conditions are removed.

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More information:
R. Burns et al, Direct isotopic evidence of the production of biogenic methane and its efflux under a temperate glacier, Scientific reports (2018). DOI: 10.1038 / s41598-018-35253-2