1. Methane Emission from Natural Wetlands in Northern Mid and High Latitudes since 1980s Xiaofeng Xu 1, Hanqin Tian 1, Vivienne Payne 2, Janusz Eluszkiewicz 2, Lori Bruhwiler 3, Steve Wofsy 4 1. Auburn University 2. Atmospheric and Environmental Research Inc. 3. National Oceanic and Atmospheric Administration 4. Harvard University

2. Acknowledgements Financial support: (NASA projects (ACMAP); DOE: DUKE UN-07-SC- NICCR-1016); NIFA McIntire-Stennis project) Drs. Mingliang Liu, Chaoqun Lu, Wei Ren, Guangsheng Chen 2

4. What is the role of natural wetlands in northern mid and high latitudes in the global methane cycle?

5. Objectives To characterize the spatial distribution of CH 4 flux in northern mid and high latitudes and its variations over time To examine the underlying mechanisms of the changes in CH 4 flux – factorial contributions (Elevated CO 2, Climate variability, Ozone pollution, nitrogen deposition) To compare with other results – Vs. inverse results & satellite results

6. Methodology Model – DLEM: Dynamic Land Ecosystem Model (Tian et al., 2010, Biogeosciences) Model driving forces – Climate: NCEP II (daily) – Fractional wetland distribution(Aselmann and Crutzen 1989; Lehner and Noll 2004) Seasonal herbaceous and woody wetlands Permanent herbaceous and woody wetlands – Others (soil, ozone, nitrogen deposition, CO 2, etc)

7. DLEM 7 Tian et al., 2010

8. Methane module Xu et al., 2010

10. Click here to view movie

11. 1980s to 1990s 1990s to 2000s Changes in CH 4 flux over the three decades

12. Methane emission in Northern mid and high latitudes from 1980 to 2008

13. 13 Simulation experiments Simulations 1Control 2Climate 3CO 2 4Ozone pollution 5Nitrogen deposition 6All combined

14. Climate variability contributed more than 95% to the accumulated CH 4 flux

15. All: simulations with all driving forces changed over time; Climate_only: simulation with climate factor changed while all others unchanged. Climate could explain more than 99 % of the interannual variations in methane flux (R 2 > 0.99)

16. Multiple linear regression also indicates that temperature is stronger than precipitation upon controlling regional CH 4 flux

17. Anomaly of CH 4 flux during 2005-2007 relative to the average between 1980 and 2008 Precipitation anomaly Temperature anomaly

18. 2003-2007 average CH 4 flux simulated by DLEM 2003-2007 average CH 4 flux derived by satellite data and an empirical method (Bloom et al., 2010) Comparison with satellite data

19. Seasonal comparison with inverse results Fraserdale, Ontario Miller et al., 2010 2004

20. Summary Methane emission from Northern mid and high latitudes showed substantial inter-annual variability during 1980-2008 and a significant increase in the first decade of 21 st century Temperature was the major factor controlling the increase of regional CH 4 emission, while precipitation control spatial changes of CH 4 flux. Spatiotemporal patterns of simulated CH 4 flux were consistent with other results derived by both bottom- up and top-down approaches

21. Future work Development of high-resolution time-series map of natural wetlands Intensive field observations in natural wetlands Wetland model improvements and comparisons Integrative study by combining bottom-up and top-down approaches

22. Thanks for your attentions!! Questions or comments??? 22