Scientists have known for a while that warming global temperatures are causing Arctic lakes to release methane, a potent greenhouse gas that leads to even more warming. In a new study published in the journal Nature, a team of researchers including U of M researcher Jacques Finlay, found that Siberian lakes have actually pulled more greenhouse gasses from the atmosphere than they have released into it since the last Ice Age, causing an overall slight cooling effect.
Permafrost, especially that in the Siberian Arctic, contains significant amounts of all organic carbon found on Earth locked away in frozen soils. Warming global temperatures in the 15,000 years since the last Ice Age have begun to thaw the permafrost, leading to the widespread formation of lakes.
"As the lakes form, they thaw sediments that have been frozen for thousands of years," Finlay said. "Previous work by the lead author and others shows that this process accelerates methane production, leading to a large atmospheric flux of this greenhouse gas."
With this continued warming over thousands of years, however, the sediment destabilizes and the lakes fill and subsequently drain. Scientists had never studied the role of thaw, or thermokarst, in lakes in the global carbon cycle past the initial burst of greenhouse gas release.
"[The goal of our study] was to try to have an understanding of the long-term carbon dynamics of these lakes," Finlay said. He and his colleagues' work, published online July 24, shows that deep thermokarst lakes have taken more carbon and greenhouse gasses from the atmosphere than they have released since the last Ice Age.
However, Finlay cautions that the lakes have buried this carbon over a period of thousands of years. He says that scientists currently cannot predict if the "ice box" effect that rapidly freezes plant matter in the permafrost will continue to do so as atmospheric temperatures rise in the short term.
|Contact: Stephanie Xenos|
University of Minnesota