The El Nio-Southern Oscillation and wetland methane interannual variability

Abstract

Global measurements of atmospheric methane (CH<inf>4</inf>) concentrations continue to show large interannual variability whose origin is only partly understood. Here we quantify the influence of the El Nio-Southern Oscillation (ENSO) on wetland CH<inf>4</inf> emissions, which are thought to be the dominant contributor to interannual variability of the CH<inf>4</inf> sources. We use a simple wetland CH<inf>4</inf> model that captures variability in wetland extent and soil carbon to model the spatial and temporal dynamics of wetland CH <inf>4</inf> emissions from 1950-2005 and compare these results to an ENSO index. We are able to explain a large fraction of the global and tropical variability in wetland CH<inf>4</inf> emissions through correlation with the ENSO index. We find that repeated El Nio events throughout the 1980s and 1990s were a contributing factor towards reducing CH<inf>4</inf> emissions and stabilizing atmospheric CH<inf>4</inf> concentrations. An increase in emissions from the boreal region would likely strengthen the feedback between ENSO and interannual variability in global wetland CH<inf>4</inf> emissions. Our analysis emphasizes that climate variability has a significant impact on wetland CH <inf>4</inf> emissions, which should be taken into account when considering future trends in CH<inf>4</inf> sources. Copyright © 2011 by the American Geophysical Union.