Modeling of microscale
variations in methane fluxes
Anu Kettunen
Jan 17th, 2003
Solar energy and
cycling of elements
2
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
3
Human activities
• Use of fossil fuel etc.
human actions
increase green house
gas concentrations =
enhances green house
phenomenon 
climate change
Indicators of the Human Influence
on the Atmosphere during the Industrial Era
Robert T. Watson, IPCC chair
4
Future climate
•
•
•
•
On average warmer
Regional differences
Precipitation patterns
Likelihood for extreme events (drought,
storms) increases
5
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
6
Methane
• CH4 important green
house gas
• Concentration
increases ca 1% per
year
• Wetlands (20-30 %),
rice paddies,
ruminants, landfills,
artificial lakes
7
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
8
Process model
9
Model predictions
800
80
800
600
60
600
80
60
400
40
400
40
200
20
200
20
5-Jul
4-Aug
3-Sep
3-Oct
-400
800
-20
6-May
-200
-40
-400
80
800
60
400
40
200
20
0
0
5-Jun
5-Jul
4-Aug
3-Sep
3-Oct
-400
800
Flux, mg CH4 m-2 d-1
600
6-May
-200
4-Aug
3-Sep
3-Oct
-20
-40
80
600
60
400
40
200
20
0
-20
6-May
-200
-40
-400
0
5-Jun
5-Jul
4-Aug
3-Sep
3-Oct
-20
-40
80
800
600
60
600
80
60
400
40
400
40
200
20
200
20
0
6-May
-200
-400
0
5-Jun
5-Jul
4-Aug
3-Sep
3-Oct
Flux, mg CH4 m-2 d-1
f. Hummock B
Water table,
cm from peat surface
e. Hummock A
Flux, mg CH4 m-2 d-1
5-Jul
d. Lawn-low hummock B
Water table,
cm from peat surface
Flux, mg CH4 m-2 d-1
c. Eriophorum lawn A
0
5-Jun
Water table,
cm from peat surface
5-Jun
0
0
-20
6-May
-200
-40
-400
0
5-Jun
5-Jul
4-Aug
3-Sep
3-Oct
Water table,
cm from peat surface
6-May
-200
0
Water table,
cm from peat surface
0
Flux, mg CH4 m-2 d-1
b. Flark B
Water table,
cm from peat surface
Flux, mg CH4 m-2 d-1
a. Carex lawn A
-20
-40
10
Fresh carbon, NPP and T
a.
4500
Flux, mg CH4 m -2 d-1
4000
3500
3000
2500
2000
1500
1000
500
0
6-May
26-May 15-Jun
5-Jul
25-Jul
14-Aug
3-Sep
14-Aug
3-Sep
23-Sep 13-Oct
800
Flux, mg CH4 m -2 d-1
700
T+2
600
500
(T&GPP)+2
400
300
T-2
200
100
0
6-May
• Model sensitive to
fresh carbon
• If T ja CO2 
 NPP 
 substrate 
 CH4 
• If only T  CH4 
less
(T&GPP)-2
26-May
15-Jun
5-Jul
25-Jul
23-Sep
13-Oct
11
Transport of oxygen to peat
c.
800
700
Flux, mg CH4 m -2 d-1
• The more sedges
transport oxygen to
peat, the lower the CH4
flux
• If methane oxidation 
 CH4 
600
500
400
300
200
100
0
6-May
26-May 15-Jun
5-Jul
25-Jul
14-Aug
3-Sep
23-Sep
13-Oct
Change in transport capacity
of sedges
12
The effect of drought
800
Flux, mg CH4 m -2 d-1
700
600
500
400
2 wk
4 wk
300
6 wk
200
100
0
6-May
8 wk
26-May
15-Jun
5-Jul
25-Jul
14-Aug
3-Sep
23-Sep
13-Oct
• Long dry periods 
methanogens  
CH4 
• If > 4-6 week
drought, no recovery
even after rains come
13
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
14