Evaluation of wetland methane emissions across North America using atmospheric data and inverse modeling
Scot M. Miller1,a,Roisin Commane2,Joe R. Melton3,Arlyn E. Andrews4,Joshua Benmergui2,Edward J. Dlugokencky4,Greet Janssens-Maenhout5,Anna M. Michalak6,Colm Sweeney7,and Doug E. J. Worthy8Scot M. Miller et al. Scot M. Miller1,a,Roisin Commane2,Joe R. Melton3,Arlyn E. Andrews4,Joshua Benmergui2,Edward J. Dlugokencky4,Greet Janssens-Maenhout5,Anna M. Michalak6,Colm Sweeney7,and Doug E. J. Worthy8
1Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
2School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
Received: 14 May 2015 – Discussion started: 23 Jun 2015 – Revised: 12 Feb 2016 – Accepted: 17 Feb 2016 – Published: 02 Mar 2016
Abstract. Existing estimates of methane (CH4) fluxes from North American wetlands vary widely in both magnitude and distribution. In light of these differences, this study uses atmospheric CH4 observations from the US and Canada to analyze seven different bottom-up, wetland CH4 estimates reported in a recent model comparison project. We first use synthetic data to explore whether wetland CH4 fluxes are detectable at atmospheric observation sites. We find that the observation network can detect aggregate wetland fluxes from both eastern and western Canada but generally not from the US. Based upon these results, we then use real data and inverse modeling results to analyze the magnitude, seasonality, and spatial distribution of each model estimate. The magnitude of Canadian fluxes in many models is larger than indicated by atmospheric observations. Many models predict a seasonality that is narrower than implied by inverse modeling results, possibly indicating an oversensitivity to air or soil temperatures. The LPJ-Bern and SDGVM models have a geographic distribution that is most consistent with atmospheric observations, depending upon the region and season. These models utilize land cover maps or dynamic modeling to estimate wetland coverage while most other models rely primarily on remote sensing inundation data.
We use atmospheric data from the US and Canada to examine seven wetland methane flux estimates. Relative to existing estimates, we find a methane source that is smaller in magnitude with a broader seasonal cycle. Furthermore, we estimate the largest fluxes over the Hudson Bay Lowlands, a spatial distribution that differs from commonly used remote sensing estimates of wetland location.
We use atmospheric data from the US and Canada to examine seven wetland methane flux estimates....
