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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. - PowerPoint PPT Presentation
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Methane Emission from Natural Wetlands in Northern Mid and
High Latitudes since 1980s
Xiaofeng Xu1, Hanqin Tian1, Vivienne Payne2,
Janusz Eluszkiewicz2, Lori Bruhwiler3, Steve Wofsy4
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
What is the role of natural wetlands in northern mid and high latitudes
in the global methane cycle?
Objectives
• To characterize the spatial distribution of CH4 flux in northern mid and high latitudes and its variations over time
• To examine the underlying mechanisms of the changes in CH4 flux
– factorial contributions (Elevated CO2, Climate variability, Ozone pollution, nitrogen deposition)
• To compare with other results– Vs. inverse results & satellite results
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, CO2, etc)
7
DLEM
Tian et al., 2010
Methane module
Xu et al., 2010
Click hereto viewmovie
1980s to 1990s
1990s to 2000s
Changes in CH4 flux over the three decades
1980 1985 1990 1995 2000 2005 201044
46
48
50
52
54
Year
Met
hane
em
issi
on (
Tg
C a
-1)
Methane emission in Northern mid and high latitudes from 1980 to 2008
13
Simulation experiments
Simulations1 Control2 Climate 3 CO2
4 Ozone pollution5 Nitrogen deposition6 All combined
1980 1985 1990 1995 2000 2005 2010-0.3-0.2-0.1
0
10
20
30
40
50A
ccum
ulat
ed m
etha
ne f
lux
(Tg
C)
Year
All Interaction Climate O3 Ndep CO2
Climate variability contributed more than 95% to the accumulated CH4 flux
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 (R2 > 0.99)
1980 1985 1990 1995 2000 2005 201042
44
46
48
50
52
54
56
550
600
650
700
750
800
850CH4 Precipitation
Year
Met
han
e fl
ux
(Tg
C a
-1)
Pre
cip
itat
ion
(m
m a
-1)
1980 1985 1990 1995 2000 2005 201042
44
46
48
50
52
54
56
-2.5
-2
-1.5
-1
-0.5
0CH4 Temperature
Year
Met
han
e fl
ux
(Tg
C a
-1)
Air
tem
per
atu
re (
C°)
Multiple linear regression also indicates that temperature is stronger than precipitation upon controlling regional CH4 flux
Anomaly of CH4 flux during 2005-2007 relative to the average between 1980 and 2008
1980 1985 1990 1995 2000 2005 201044
46
48
50
52
54
Year
Met
han
e em
issi
on (
Tg
C
a-1)
Precipitation anomaly
Temperature anomaly
2003-2007 average CH4 flux simulated by DLEM
2003-2007 average CH4 flux derived by satellite data and an empirical method (Bloom et al., 2010)
Comparison with satellite data
Seasonal comparison with inverse results
0
0.02
0.04
0.06
0.08
0.1
Estimated CH4 flux in Hundson Bay Low-land wetland
Inverse model
Process-based model
Month
Met
hane
flux
(gC
m-2
day
-1)
Fraserdale, OntarioMiller et al., 2010
2004
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 21st century
• Temperature was the major factor controlling the increase of regional CH4 emission, while precipitation control spatial changes of CH4 flux.
• Spatiotemporal patterns of simulated CH4 flux were consistent with other results derived by both bottom-up and top-down approaches
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???