Assessing the Contribution of Climate Change to the Arctic Methane Budget

Recent observations of CH₄ emissions from underwater CH₄ hydrates and permafrost regions raise two questions: 1) What is the impact of these emissions on the Arctic and global CH₄budget; and 2) Are these emissions increasing due to warming that has been observed in the Arctic? Recent aircraft data collected over Alaska from April through November show that atmospheric methane concentrations are predominantly controlled by transport from lower latitudes although the stratosphere and nearby ocean and terrestrial sources have impact on smaller temporal and spatial scales. Similarly, a 26 year record of ground observations made at Barrow, AK, also shows a broad seasonal cycle which is largely controlled by lower latitude processes and higher frequency events which originate from both natural and anthropogenic point sources in the Arctic region. Despite significant inter annual variability, there is no evidence of a significant rise in CH₄ concentrations due either to natural or anthropogenic sources in the Arctic. This presentation will review the major contributors to the methane seasonal cycle over Alaska using the NOAA/ESRL long term dataset, as well as recent aircraft observations that the NOAA Carbon Cycle Group is making in collaboration with the U.S. Coast Guard. This study illustrates the need for coordinated efforts to combine small-scale direct flux measurements with concentration measurements made from both tall towers and aircraft over multiple years.