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)

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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

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50

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54

Year

Met

hane

em

issi

on (

Tg

C a

-1)

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

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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

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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

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48

50

52

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-2.5

-2

-1.5

-1

-0.5

0CH4 Temperature

Year

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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

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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

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Thanks for your attentions!!

Questions or comments???