Long-term Observation of CO2 concentration and its isotope ratios over the Western Pacific

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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
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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.
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Alligator Hope(MOL)
92 93 94 95 96 97 98 99 00
01 02 03 04 05 06 07
SKAUBRYN(Seaboard)
NOV
Japan - N America (30N-55N)
SKAUGRAN (Seaboard)
PYXIS(TOYOFUJI)
Japan Oceania (30N-35S)
Southern Cross
Hakuba
FUJITRANS WORLD
Golden Wattle(MOL)
Trans Future
Special thanks to MOL, Toyofuji, Fuji Trans,
Nihhon Usen, Seaboard International Shipping Co.
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FUJITRANS WORD and PYXIS routes 2003 Sep 2004
Nov
PYXIS
FUJITRANS WORLD
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• 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

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GPS sensor
Temperature sensor
Air Inlet
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Sampling Controller
GPS receiver
CO2 analyzer
(3) Sampling Flask Box
(2) Cooler (-45 oC)
(1) Metal bellows pump
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Isotope signature of CO2 (13C, 14C, 18O) will
provide important clues about CO2 budget and
climatic effects on CO2 uptake mechanism
12CO2
13CO2
14CO2
C3 plant
12C18O2
H218O
C4 plant
Soil
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40N-50N
20N-30N
CO2
Delta 13C
Delta 18O
0-10N
20S-10S
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Carbon isotope ratio
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Latitudinal distribution
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CO2 growth rate (ppm/y)
Delta 13C change rate (per mil/y)
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Simple Global Flux Estimation
12C flux dCa/dt CF CNs CNb
------------------(1) 13
C flux dd13Ca/dt CFdF CNs(da eas)
CNb(da eab)
CGs(ds da) CGb(db da) ------(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(ds
da) CGb(db da) 93 Gt-C per mli / year
(Francey et al )
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Preliminary estimation of flux
Anthropogenic input
Atmosphere
Land Biosphere
Ocean
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15S
25N
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Biomass burning signal can be detected ?
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A preliminary guess of net Carbon flux budget
(PgC/y) to assess isotope signature and its
usability
These values for terrestrial and oceanic sinks
may have a large uncertainty (over 1Pg/y)
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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?
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Apparent variation of oceanic sink can be
compensated by biological discrimination
adjustment by up to 0.2 per mil
SOI
0.2 per mil decrease can be possible by high T
and low humidity , but Gross primary production
can not decrease by corresponding amount (over
50)
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Delta 18O trend showed some increase over 10 years
SOI
Increase delta 18O of water? GPP decrease?
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• Conclusion
• 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
  1990s. 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)

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Seasonal component and biological discrimination
Apparent Biological discrimination -19 per mil
Source and sink delta 13C
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CF Merland dF -28 per mil (estimated) eas 1.8
per mil eab 19 per mil Gb 125PgC/y Go
90PgC/y Disequilibrium Sea-Atmosphere 0.6 per
mil Disequilibrium Terrestrial biosphere-Atmospher
e 0.394 as standard case
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CO2 trend in each latitude
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13C isotope ratio trend in each latitude
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Oxygen isotope ratio
delta 18O
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Sampling inlet