Greenland meltwater flushes methane to the atmosphere

It has been suggested that ice sheets may influence past and future atmospheric methane concentrations, but direct evidence for the existence of subglacial methane remains scarce. This paper reports that subglacially produced methane is rapidly flushed to the ice margin by the efficient drainage system of a subglacial catchment of the Greenland Ice Sheet. Atmospheric evasion is found to be the main methane sink once runoff reaches the ice margin, with estimated diffusive methane fluxes similar to those of major world rivers. Overall, the results suggest that certain glacial environments may have to be considered a previously underappreciated component of the Earth’s methane budget.