Methane seepage in the Arctic: GI's Grosse and colleagues' work in Nature Geoscience
In an article that highlights findings of geologic methane seepage in zones of Arctic permafrost thaw and receding glaciers, Geophysical Institute Research Assistant Professor Guido Grosse and colleagues share results that indicate a warmer future will release more methane, swelling the greenhouse gas budget. The article, led by Katey Walter of the Institute of Northern Engineering and co-authored by Grosse and two others appeared in Nature Geoscience in May.
Here's the abstract for the paper:
Methane, a potent greenhouse gas, accumulates in subsurface hydrocarbon reservoirs, such as coal beds and natural gas deposits. In the Arctic, permafrost and glaciers form a ‘cryosphere cap’ that traps gas leaking from these reservoirs, restricting flow to the atmosphere. With a carbon store of over 1,200 Pg, the Arctic geologic methane reservoir is large when compared with the global atmospheric methane pool of around 5 Pg. As such, the Earth’s climate is sensitive to the escape of even a small fraction of this methane. Here, we document the release of 14C-depleted methane to the atmosphere from abundant gas seeps concentrated along boundaries of permafrost thaw and receding glaciers in Alaska and Greenland, using aerial and ground surface survey data and in situ measurements of methane isotopes and flux. We mapped over 150,000 seeps, which we identified as bubble-induced open holes in lake ice. These seeps were characterized by anomalously high methane fluxes, and in Alaska by ancient radiocarbon ages and stable isotope values that matched those of coal bed and thermogenic methane accumulations. Younger seeps in Greenland were associated with zones of ice-sheet retreat since the Little Ice Age. Our findings imply that in a warming climate, disintegration of permafrost, glaciers and parts of the polar ice sheets could facilitate the transient expulsion of 14C-depleted methane trapped by the cryosphere cap.
Find out more at http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1480.html.
FIGURE CAPTION: a, Yellow dots, representing 77 subcap seep sites identified across Alaska in this study, and green dots (superficial study lakes) are scaled by the magnitude of methane flux (kg CH4 site−1 d−1) at each site. Black dashed lines show sections of the flight path omitted from analysis due to fog. b, Study regions, yedoma deposits and hydrocarbon basins. Further map source information is provided in the Supplementary Information. Few additional records of natural fossil methane seepage in the terrestrial Arctic have been documented in Canada and Russia6, 16.