Methane-eating bacteria in lake deep beneath Antarctic ice sheet may reduce greenhouse gas emissions

An interdisciplinary team of researchers has concluded that bacteria in a lake 800 meters (2,600 feet) beneath the West Antarctic Ice Sheet may digest methane, a powerful greenhouse gas, preventing its release into the atmosphere.

Frank Rack, of the University of Nebraska-Lincoln, at the WISSARD test-driliing site in December 2012. Image credit: Peter West, NSF

As part of the NSF-funded Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project, the researchers successfully drilled through the ice sheet in 2013 to reach Lake Whillans. They retrieved water and sediment samples from a body of water that had been isolated from direct contact with the atmosphere for many thousands of years.

The prevalence of methane-consuming bacteria in the upper lake sediment suggests a "methane biofilter" prevents the gas from entering the subglacial water, where it can eventually drain into the ocean and be released into the atmosphere. The bacteria obtain energy from digesting the methane.

The team, which includes researchers from Montana State University, Louisiana State University and Aberystwyth University in Wales, used a combination of measurements of methane concentrations and genomic analyses to describe how lake bacteria chemically convert methane in a way that reduces the warming potential of subglacial gases during ice sheet retreats.

The scientists say that if their analysis is correct, it could mean that a large reservoir of methane thought to lie under the vast West Antarctic Ice Sheet -- which encompasses 25.4 million cubic kilometers (6.1 million cubic miles) of ice -- is less likely to be released into the atmosphere.

They also note that because methane is such a potent greenhouse gas, "understanding its global sources, sinks and feedbacks within the climate system is of considerable importance" to the scientific understanding of the larger global climate picture.

Their findings describe how biological processes in the sediments at the lake bottom transform the methane into carbon dioxide. This area, where the water meets the lake bottom, may be vital to the success of ecosystems of subglacial lakes, which are permanently cut off from atmospheric heat and sunlight.

Studies of subglacial lakes may contain clues as to how microbial life might persist in the outer solar system, where ice-covered moons orbit the larger planets. (National Science Foundation)

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