Despite large temperature increases in Alaska in recent decades, a new analysis of NASA airborne data finds that methane is not being released from Alaskan soils into the atmosphere at unusually high rates, as recent modeling and experimental studies have suggested. The new result shows that the changes in this part of the Arctic have not yet had enough impact to affect the global methane budget.
This is important because methane is the third most common greenhouse gas in the atmosphere, after water vapor and carbon dioxide. Although there is much less of it in the air, it is 33 times more effective than carbon dioxide at trapping heat in the atmosphere and adding to greenhouse warming.
High concentrations of atmospheric methane have been measured at individual Arctic sites, especially in Siberia. This adds to the concern that massive methane releases are already occurring in the far North. NASA’s multiyear Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) is the first experiment to establish emission rates for a large region of the Arctic.
In the new study, researchers analyzed methane measurements made over Alaska from May through September 2012 during the first season of CARVE. They estimated emission rates for the winter months, during most of which no methane was released because the soil was frozen.
Alaska composes about one percent of Earth’s total land area, and its estimated annual emissions in 2012 equaled about one percent of total global methane emissions. That means the Alaskan rate was very close to the global average rate.
“That’s good news, because it means there isn’t a large amount of methane coming out of the ground yet,” said lead author Rachel Chang, formerly at Harvard University, Cambridge, Massachusetts, and now an assistant professor and Canada Research Chair in Atmospheric Science at Dalhousie University, Halifax, Nova Scotia.
image credit NASA/JPL-Caltech
