Cows are a red herring. The most dangerous potential source for methane release lies underneath thinning permafrost and glaciers in the Arctic. Ecologists have just mapped the seeps where methane is bubbling up, and they found more than 150,000 of them.
Methane is a seriously potent greenhouse gas. Compared to a single molecule of carbon dioxide, methane is 25 times stronger, according to Katey Walter Anthony, an aquatic ecosystem ecologist at the University of Alaska Fairbanks who led the new mapping research. She and her colleagues just published their findings in Nature Geoscience (abstract).
You might know Walter Anthony from YouTube videos, where she and her students illustrate methane release by stabbing pockets frozen in an Alaskan lake and setting the gas on fire. That lake thaws every summer and then winter ice covers the gas bubbles, trapping them. Far thicker caps have been trapping methane year-round in the Arctic, but little was known about how they were holding up. Until now.
The effect on lake ice formation of subcap and superficial seeps. a–c, Photographs showing examples of the largest superficial seeps (a) and small (b) and large (c) subcap macroseeps. Even the strongest superficial seeps are ice-covered in late winter. Further, bubbling up does not occur simultaneously among superficial seeps (a). In contrast, bubbles breaking the surface of all open holes indicate high, simultaneous bubbling up among subcap seeps (b). d, Clustering of subcap seeps is apparent in the aerial photograph. Photographs were taken near Fairbanks, interior Alaska (a), Cook Inlet, southcentral Alaska (b) and Atqasuk, northern Alaska (c,d) one, eight and three weeks, respectively, following freeze-up. (Walter Anthony, Nature Geoscience)
Walter Anthony and her colleagues combined Arctic aerial survey data with ground-based measurements to document widespread methane seeps along melting glaciers and permafrost for the first time. They looked at both superficial methane seepage from shallow lakes and wetland, as well as seepage from what they call "subcaps" -- the thicker ice cap.
The scientists discovered 77 subcap seep sites that had never been documented before. In those areas, they recorded more than 150,000 single bubble streams of methane. Most of the methane escape occurred where permafrost was thawing and glaciers retreating.
"In a warmer world, thawing permafrost and wastage of glaciers and ice sheets could lead to a significant transitional degassing of subcap methane," the authors wrote in Nature Geoscience. In other words, time will reveal just how much of a Michael Bay movie we'll be watching unfold in the Arctic.