Potential Changes in Methane Emissions From Arctic Wetlands: How Small a Change can we Observe With the Current Observing Network?

Increasing temperature and melting permafrost in Siberia could result in substantially increased CH4 emissions from northern wetlands. This raises two important questions. First, have northern wetland emission rates already increased, and, second, how much of an increase in emissions is necessary before it can be observed with current atmospheric air sampling networks? Measurements of atmospheric CH4 from a globally-distributed network of air sampling sites indicate that any permanent increase in emissions since 1999 from high northern latitudes is small and has been balanced by decreased emissions from other emission sectors. Using a chemical transport model, we show that increases in emissions on order of 10 Tg CH4 yr-1 (or about 30% of northern wetland emissions) can be observed as a change in the difference in CH4 abundance between northern and southern polar regions. Observed changes in the seasonal cycle phase and amplitude may also be useful, but this method may be limited by significant interannual variability in the CH4 seasonal cycle at high northern latitudes. Measurements of CH4 total column abundance by satellite (SCIAMACHY) over the continents, with much greater spatial coverage than surface measurements, may also be useful in identifying changes in emissions from northern wetlands. We will present current information available from SCIAMACHY on northern wetland emissions and assess the magnitude of signal that would be detectable with changing emissions.