The Greenland Ice Sheet emits tons of methane over the summer according to a new study, showing that biological activity beneath the ice impacts the atmosphere far more than previously thought.
We camped for 3 months next to the Greenland Ice Sheet, sampling the meltwater that runs off a large catchment (> 600 km2) of the ice sheet during the summer months. Using novel sensors to measure methane in meltwater runoff in real time, we observed that methane was continuously exported from beneath the ice during summer. We calculated that at least six tons of methane was transported to their measuring site from this portion of the ice sheet alone. But the amount of methane released to the atmosphere could be much larger, and accurately measuring how much of the gas diffuses to the atmosphere requires further study.
These results confirm previous assertions that ice sheet beds are methanogenic wetlands, and that where there is an active hydrological system, methane produced can escape the ice sheet via fast flowing rivers and enter the atmosphere. The fact that the melting of the ice sheet will accelerate in the coming decades will likely be reflected in the increasing amounts of methane released from under the ice. The microbes living kilometres beneath the ice may therefore represent another factor in the ongoing climate change, one that has so far been ignored.
(Yet another paper from the great 2015 Camp Doom field season!)
Lamarche-Gagnon G, Wadham JL, Sherwood Lollar B, Arndt S, Fietzek P, Beaton AD, Tedstone AJ, Telling J, Bagshaw EA, Hawkings JR, Kohler TJ, Zarsky JD, Mowlem MC, Anesio AM, Stibal M (2019) Greenland melt drives continuous export of methane from the ice-sheet bed. Nature 565:73–77 doi: 10.1038/s41586-018-0800-0