Major Source of Atmospheric Methane Identified Near Arctic Lakes
Talk about your ugly positive feedbacks: according to a team of researchers based at the University of Alaska, Fairbanks, a source of methane - which likely originated during the last ice age - has surfaced in the Arctic, a likely result of global warming's thawing effect on the permafrost. Methane bubbling from this source could have accounted for up to 87% of the observed spike in atmospheric methane.
"It tells us that this isn't just something that is ongoing now. It would have been a positive feedback to climate warming then, as it is today. We estimate that as much as 10 times the amount of methane that is currently in the atmosphere will come out of these lakes as permafrost thaws in the future. The timing of this emission is uncertain, but likely we are talking about a time frame of hundreds to thousands of years, if climate warming continues as projected," said lead scientist, Katey Walter, whose study appeared in last week's issue of Science.
Scientists had previously discovered that a rapid increase in atmospheric methane levels in the early Holocene was caused by an "unidentified northern source". Past studies had suggested that gas hydrates or wetlands could have been to blame for the spike; Walter's research has now shown that methane bubbling from thermokarst lakes was a major source.
The lakes, which form when the surrounding permafrost thaws, "really flared up ... emitting huge amounts of methane," Walter concluded. "All that carbon that had been locked up in the ground for thousands of years is converted to potent greenhouse gases: methane and carbon dioxide ... This suggests that large releases from lakes may occur again in the future with global warming."