• greenhouse gases;
  • methane emissions

Methane, a potent greenhouse gas that contributes to climate change, enters the atmosphere from a variety of sources—it can leak from industrial gas fields or pipelines, escape from submarine hydrates that decompose with warming temperatures, or be released from decaying organic matter. Methanes from different sources have different isotopic compositions, allowing researchers to identify the source of methane in the air, as Fisher et al. have done in a new study. The researchers analyzed the isotopic composition of methane in the air off Spitsbergen, Norway, in 2008 and 2009. They found that in the summer, wetlands were the dominant methane source. Methane is being released to the water column from gas hydrates on the seabed, but so far, the study indicates, this methane has not reached the atmosphere. Wetlands are likely to release more methane as temperatures warm, feeding further climate change. (Geophysical Research Letters, doi:10.1029/2011GL049319, 2011)