High levels of methane is escaping from the thawing subsea permafrost but the source(s) of that methane has long remained elusive. Now, a new study shows, for the first time, that the methane originates largely from a thermogenic (natural gas) deposit that breaks through the subsea permafrost and release into the shallow water column and the overlying atmosphere. The study was published recently in Proceedings of the US National Academy of Sciences.
The study’s main authors, research engineer Henry Holmstrand and former postdoctoral scientist Julia Steinbach, were members of the international team that located the source of the methane. This was made possible by applying high-precision triple-isotope fingerprinting on seawater samples collected onboard the icebreaker Oden during Arctic expedition SWERUS-C3 in 2014. This method allowed the team to determine the isotope composition of the methane in the water samples.
“The isotope composition of the evading methane reflects its formation mechanism and regime and can thus be used to deduce the source. Being able to identify the source of the extensive methane releases is a key underpinning toward predictions of how the releases of this strong greenhouse will develop in the coming period” says Professor Örjan Gustafsson, corresponding author and Chief Scientist on SWERUS-C3.