Modeling of microscale variations in methane fluxes

Anu Kettunen

Jan 17th, 2003

2

Solar energy and cycling of elements

3

Natural green house phenomenon• Atmosphere surface

temperature of Earth ca 30oC higher than without atmosphere

• Green house gases prevent Solar energy from escaping from Earth

• H2O, CO2, CH4, N2O, CFC compounds

4

Human activities

• Use of fossil fuel etc. human actions increase green house gas concentrations = enhances green house phenomenon climate change

Indicators of the Human Influenceon the Atmosphere during the Industrial Era

Robert T. Watson, IPCC chair

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Future climate

• On average warmer

• Regional differences

• Precipitation patterns

• Likelihood for extreme events (drought, storms) increases

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Mires• Northern mires carbon

sinks during last millenia, huge amount of carbon in peat

• Sources of green house gases (CO2 ja CH4)

• Important to understand role of mires in carbon cycle

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Methane

• CH4 important green house gas

• Concentration increases ca 1% per year

• Wetlands (20-30 %), rice paddies, ruminants, landfills, artificial lakes

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Research problem

• Previously no satisfactory description of spatial and seasonal variations in methane fluxes

• Growing season measurument: CH4, T, WT etc. from different mire surfaces

• Methane production and oxidaton potentials• Process model connects methane flux to

vegetation cover, photosynthetic cycle and peat thermal and moisture conditions

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Process model

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Model predictions

a. Carex lawn A

-400

-200

0

200

400

600

800

6-May 5-Jun 5-Jul 4-Aug 3-Sep 3-OctFlu

x, m

g C

H4

m-2

d-1

-40

-20

0

20

40

60

80

Wat

er t

able

,cm

fro

m p

eat

surf

ace

b. Flark B

-400

-200

0

200

400

600

800

6-May 5-Jun 5-Jul 4-Aug 3-Sep 3-OctFlu

x, m

g C

H4

m-2

d-1

-40

-20

0

20

40

60

80

Wat

er t

able

,cm

fro

m p

eat

surf

ace

c. Eriophorum lawn A

-400

-200

0

200

400

600

800

6-May 5-Jun 5-Jul 4-Aug 3-Sep 3-OctFlu

x, m

g C

H4

m-2

d-1

-40

-20

0

20

40

60

80

Wat

er t

able

,cm

fro

m p

eat

surf

ace

d. Lawn-low hummock B

-400

-200

0

200

400

600

800

6-May 5-Jun 5-Jul 4-Aug 3-Sep 3-OctFlu

x, m

g C

H4

m-2

d-1

-40

-20

0

20

40

60

80

Wat

er t

able

, cm

fro

m p

eat

surf

ace

e. Hummock A

-400

-200

0

200

400

600

800

6-May 5-Jun 5-Jul 4-Aug 3-Sep 3-OctFlu

x, m

g C

H4

m-2

d-1

-40

-20

0

20

40

60

80

Wat

er t

able

, cm

fro

m p

eat

surf

ace

f. Hummock B

-400

-200

0

200

400

600

800

6-May 5-Jun 5-Jul 4-Aug 3-Sep 3-OctFlu

x, m

g C

H4

m-2

d-1

-40

-20

0

20

40

60

80

Wat

er t

able

,cm

fro

m p

eat

surf

ace

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Fresh carbon, NPP and T

0

500

1000

1500

2000

2500

3000

3500

4000

4500

6-May 26-May 15-Jun 5-Jul 25-Jul 14-Aug 3-Sep 23-Sep 13-Oct

Flu

x,

mg

CH

4 m

-2 d

-1

a.

• Model sensitive to fresh carbon

• If T ja CO2 NPP substrate CH4

• If only T CH4 less

0

100

200

300

400

500

600

700

800

6-May 26-May 15-Jun 5-Jul 25-Jul 14-Aug 3-Sep 23-Sep 13-Oct

Flu

x,

mg

CH

4 m

-2 d

-1

(T&GPP)-2

(T&GPP)+2

T+2

T-2

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Transport of oxygen to peat

• The more sedges transport oxygen to peat, the lower the CH4 flux

• If methane oxidation CH4

0

100

200

300

400

500

600

700

800

6-May 26-May 15-Jun 5-Jul 25-Jul 14-Aug 3-Sep 23-Sep 13-Oct

Flu

x,

mg

CH

4 m

-2 d

-1

c.

Change in transport capacity of sedges

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The effect of drought

• Long dry periods methanogens CH4

• If > 4-6 week drought, no recovery even after rains come

0

100

200

300

400

500

600

700

800

6-May 26-May 15-Jun 5-Jul 25-Jul 14-Aug 3-Sep 23-Sep 13-Oct

Flu

x,

mg

CH

4 m

-2 d

-1

8 wk

6 wk4 wk

2 wk

14

Main contribution of the thesis• Simulation model for CH4 fluxes from

different mire surfaces CH4 fluxes from boreal mires can be predicted under current and future climate

• Increased understanding

• Connection to general circulation models