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Long-term Observation of CO2 concentration and its
isotope ratios over the Western Pacific
H. Mukai, Y. Nojiri, Y. Tohjima, T. Machida,
Y. Shibata and H. Kitagawa
Center for Global Environmental Research,
National Institute for Environmental Studies
And
Nagoya University
Monitoring by using commercial cargo ships
Atmospheric CO2 samples from wide range of latitude can be
colleted.
Frequent commercial cargo ship service enable us to observed
seasonal variation of CO2 in addition to long-term variation.
Japan-Oceania cruise can provide us a good chance to observe
latitudinal difference in behavior of CO2 from Northern
Hemisphere to Southern Hemisphere.
Relatively economic monitoring if it goes as planed.
Alligator Hope（MOL)
92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07
NOV
SKAUBRYN（Seaboard)
Japan -
N America
(30N-55N) SKAUGRAN （Seaboard) PYXIS(TOYOFUJI)
Japan – Southern Cross
Hakuba
Oceania
Golden Wattle(MOL) FUJITRANS WORLD
(30N-35S)
MOL Glory Trans Future
Special thanks to MOL, Toyofuji, Fuji Trans, Nihhon Usen,
Seaboard International Shipping Co.
FUJITRANS WORD and PYXIS routes
2003 Sep – 2004 Nov
PYXIS
FUJITRANS WORLD
1) Bottle Sampling :
Stainless-steel bottle 3L (+ Glass bottle 2.5L )
~10 times/y since 1995
~ 3 samples / 10 degree in latitude
2) Gas analysis in the bottle:
CO2, N2O, CH4 (NDIR, GC-ECD, GC-FID)
delta 13C, delta 18O (MAT252, dual inlet)
14C is measured by Accelerator MASS in NIES
GPS sensor Temperature sensor
Air Inlet
Sampling Controller
GPS receiver
CO2 analyzer
(3) Sampling Flask Box
(2) Cooler (-45 oC)
(1) Metal bellows pump
Isotope signature of CO2 (13C, 14C, 18O)
will provide important clues about CO2 budget
and climatic effects on CO2 uptake mechanism
14CO 12CO 13CO
2 2 2
C3 plant
18O 12C18O
H2 2
C4 plant Soil
(N40-N50) (N40-N50) (N40-N50)
385 -7.4 1.2
380 -7.6 0.8
Delta C13 (per mil)
Delta O18 (per mil)
0.4
375 -7.8
CO2 (ppm)
0
370 -8 -0.4
365 -8.2 -0.8
360 40N-50N -8.4
-1.2
-1.6
355 -8.6 -2
350 -8.8 -2.4
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
(N20-N30) (N20-N30)
(N20-N30)
385 -7.4 1.2
Delta C13 (per mil)
380 -7.6 0.8
Delta O18 (per mil)
375 -7.8 0.4
CO2 (ppm)
0
370 -8
-0.4
365
360
20N-30N -8.2
-8.4
-0.8
-1.2
355 -8.6 -1.6
350 -8.8 -2
-2.4
CO2
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
(0-N10) Delta 13C
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
(0-N10)
Delta 18O
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
385 (0-N10)
380 -7.4 1.2
-7.6 0.8
Delta C13 (per mil)
Delta O18 (per mil)
375
CO2 (ppm)
0.4
370 -7.8
0
365 -8 -0.4
360
355
0-10N -8.2
-8.4
-0.8
-1.2
-1.6
350 -8.6 -2
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 -8.8 -2.4
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
(S20-S10)
(S20-S10)
385 (S20-S10)
-7.4 1.2
380 -7.6 0.8
Delta C13 (per mil)
Delta O18 (per mil)
375 -7.8 0.4
CO2 (ppm)
370 0
-8
-0.4
365 -8.2 -0.8
360 -8.4 -1.2
355 20S-10S -8.6
-1.6
-2
350 -8.8 -2.4
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Carbon isotope ratio
6 Latitudinal distribution
CO2 deviation from 35S (ppm)
5
4
CO2 concentration
3
2
1
0
0.05
-1
Delta 13C deviation from 35S (per mil)
-40 -20 0 20 40 60
-0.05 Latitude
-0.15
-0.25
Delta 13C
-0.35
-40 -20 0 20 40 60
Delta 13C change rate (per mil/y)
delta 13C change rate (per mil/y) CO2 growth rate (ppm/y)
CO2 Growth rate (ppm/y)
0.5
1.5
2.5
3.5
0
1
2
3
-0.08
-0.06
-0.04
-0.02
-0.1
0
0.02
0.04
1995 1995
1996 1996
1997 1997
1998 1998
1999 1999
2000 2000
2001 2001
2002 2002
2003 2003
2004 2004
2005 2005
30S-10S
30S-10S
10S-10N
30N-50N
10N-30N
10S-10N
30N-50N
10N-30N
Simple Global Flux Estimation
12C flux
dCa/dt = CF + CNs + CNb Biological ------------------(1)
13C flux Discrimination
dδ13Ca/dt = CFδF+ CNs(δa +εas) + CNb(δa +εab)
+ CGs(δs –δa) + CGb(δb –δa) ------(2)
CF = anthropegenic input ( Fossil combustion and Cement production)
CNs = Net Sea flux
CNb = Net land biological flux
CGS = Gross exchange flux between Sea and atmosphere
CGb = Gross exchange flux between land biosphere and atmosphere
Isotope disequilibrium term CGs(δs –δa) + CGb(δb –δa)
= 93 Gt-C per mli / year (Francey et al )
Preliminary estimation of flux
Anthropogenic CO2 input Land
Ocean CO2 in the atmosphere
8
Anthropogenic input
6
Atmosphere
Atmosphere
Flux (Gt-C / y), SOI
4
Land
Land Biosphere
2
0
-2
Ocean
Ocean
-4
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Anthropogenic CO2 input Land
Ocean CO2 in the atmosphere
SOI Temp Anomaly
8 1
0.9
6 Atmosphere Temp 0.8
Global Temp. Anomaly
Flux (Gt-C / y), -SOI
0.7
4
0.6
2 0.5
-SOI
0.4
0
0.3
0.2
-2 Land
Ocean 0.1
-4 0
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
15S
25N
Biomass burning signal can be detected ?
A preliminary guess of net Carbon flux budget (PgC/y)
to assess isotope signature and its usability
Terrestrial Oceanic Atmospheric Anthropogenic
1996 -1.5 -2.1 2.9 6.5
1997 -0.1 -3.0 3.6 6.7
1998 0.1 -2.1 4.7 6.7
1999 -1.6 -1.5 3.4 6.5
2000 -2.5 -1.3 2.9 6.7
2001 -1.4 -1.6 3.9 6.8
2002 -0.1 -1.6 5.3 7.0
2003 -0.9 -1.3 4.8 7.0
2004 -2.7 -1.1 3.2 7.0
Avearge -1.2 -1.7 3.9 6.8
These values for terrestrial and oceanic sinks may have a
large uncertainty (over +1Pg/y)
Assessment of isotopic balance equation
Oceanic sink looked too variable.
Oceanic sink variation = +1 PgC and decrease trend ???
c.f. Reported oceanic variation on flux is about +0.4 PgC
What is possible causes ?
If we set Oceanic sink variation to be Zero
How much percent we have to change the parameters such as
Discrimination factor? It is most important for both disequilibrium
and biological uptake term.
1) Discrimination for CO2 uptake by plants
fractionation factor decreases?
C4 plant fraction to C3 plant increase?
2) Gross primary production decreases or increase?
Apparent variation of oceanic sink can be compensated
by biological discrimination adjustment by up to 0.2 per mil
-18.6 2
Discrimination expected (per mil)
0
-18.7 SOI
-2
-18.8 0.2 per mil decrease can be possible
by high T and low humidity , but -4
SOI
Gross primary production can not
-18.9 -6
decrease by corresponding amount
(over 50%) -8
-19
-10
-19.1 -12
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
Delta 18O trend showed some increase over 10 years
2 2
-25
delta 18O trend (per mil)
1.5 -1
SOI
-15
1 -4
-5
0.5 -7 5
0 -10 15
25
-0.5 -13
El Nino
35
-1 -16
Increase delta 18O of water? GPP decrease?
45
-1.5 -19 55
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
SOI
Conclusion
(1) Ten-year observation of CO2 and isotopes over Western Pacific from 30S to 50N
was conducted by using 8 commercial cargo ships.
(2) By simple carbon budget equations using isotopic data, oceanic and terrestrial
uptake amounts were estimated. Oceanic sink was relatively stable but still had
1Pg-C variation. Terrestrial sink seemed to decrease rapidly by higher and more
dry condition at El Nino event. Apparent oceanic fluctuation may be partly
caused by the change of C isotopic discrimination due to climatic condition.
(3) Oxygen isotope ratio showed increasing trends in all latitude during 10 years.
It was different tendency from that of 1990’s. It may be related to high
temperature and low humidity tendency including lower GPP in recent years.
(4) Carbon-14 measurements will give an another angle to look at carbon budget.
Further analysis is needed.
(5) Seasonal variations of CO2 and carbon isotope ratio were large in Northern
Hemisphere but small in Southern Hemisphere. Isotope fractionation factor was
about –19 per mil on average, but –14 per mil in 20S, which showed some C4
plants effect at that latitude. (not shown)
Seasonal component and biological discrimination
Keeling Geometric mean Tans
keeling classic Delta (Tans )
Delta (Keeling Classic) Delta (Geometric mean)
-10
-12 Apparent Biological discrimination
delta 13C (per mil)
-14 -19 per mil
-16
-18
-20
-22
-24 Source and sink delta 13C
-26
-28
-30
-30 -20 -10 0 10 20 30 40 50
Latitude
CF: Merland
δF: -28 per mil (estimated)
εas: 1.8 per mil
εab: 19 per mil
Gb: 125PgC/y
Go: 90PgC/y
Disequilibrium Sea-Atmosphere: 0.6 per mil
Disequilibrium Terrestrial biosphere-Atmosphere: 0.394 as
standard case
CO2 trend in each latitude
385
-25
380 -15
CO2 trend (ppm)
375 -5
5
370
15
365 25
35
360
45
355 55
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
13C isotope ratio trend in each latitude
-7.8
-25
delta 13C trend (per mil)
-7.9
-15
-8 -5
-8.1 5
-8.2 15
-8.3 25
35
-8.4
45
-8.5 55
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Oxygen isotope ratio
delta 18O
Anthropogenic CO2 input Land
Ocean CO2 in the atmosphere
8
6
Atmosphere
Flux (Gt-C / y), SOI
4
Land
2
0
-2
Ocean
-4
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Sampling inlet
