CARBON CYCLE

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CARBON CYCLE AND ANTHROPOGENIC CARBON Aida
F.Ríos Departamento de Oceanografía Instituto de
Investigaciones Marinas. CSIC. C/Eduardo
Cabello, 6. 36208-Vigo, Spain. Email
aida_at_iim.csic.es
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• Role of the Ocean
• Distributing the solar energy.
• Regulating the CO2
• concentration of the atmosphere.

• GLOBAL CARBON CYCLE
• CO2 UPTAKE FROM THE ATMOSPHERE
• ANTHROPOGENIC CARBON

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Air-Sea
Acumulation
Circulation
Pg 1015 g
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• The Carbon cycle in the ocean is governed by
  three factors
• Physical Pump (the solubility of CO2 in
  seawater)
• Air-Sea interface CO2 Exchange
• Biological Pump (biochemical cycling of ocean
  carbon)
• Uptake of CO2 by photosynthesis in the upper
  ocean and exported to the deep ocean.
• Ocean water circulation
• Distribution of the oceanic CO2

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CO2 UPTAKE FROM THE ATMOSPHERE
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(Takahashi et al., 2002)
Average Net Annual Flux 2.2 0.45 Pg/yr
FCO2 0.24kS(fCO2sea-fCO2air) k
is the transfer velocity coefficient f(wind), S
is the CO2 solubility in seawater f(S, T),
0.24 is a conversion factor between units
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Seasonal Sea-surface CO2 in AZORES area
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CO2 uptake in the North Atlantic Drift Region
Average wind 5.0 ?0.6 m s-1 SST 13.8 ?0.5
ºC Wanninkohf (1992) 0.76 mol m-2
y-1 Liss and Merlivat (1986) 0.43 mol m-2
y-1
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ANTHROPOGENIC CARBON
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WOCE/JGOFS/OACES Global CO2 Survey 1991-1997
Total number of carbon sample locations
100,000 TCO2 estimated accuracy 2-4 µmol
kg-1 Alkalinity estimated accuracy 4-5 µmol kg-1
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The back-calculation technique to estimate CANT

• Assuming that
• dissolved oxygen and CO2 are close to equilibrium
  with the atmosphere during water mass formation.
• alkalinity is not significantly affected by the
  CO2 increase

CANT CT AOU/RC ½(?TA AOU/RN ) - CT?

• CT is the current total inorganic carbon
• ?TA TA - TA0, current alkalinity - preformed
  alkalinity
• AOU is the Apparent Oxygen Utilization O2sat
  O2meas
• RC (DO2/DC) and RN (DO2/DN) are stoichiometric
  coefficients
• CT? is the inorganic carbon in equilibrium with
  the preindustrial atmosphere.

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The back-calculation technique to estimate CANT
Improvements made by Pérez et al., 2002

• Effect of water vapour pressure on the
  estimation of the pre-industrial pCO2
• Appropiate carbonic acid dissociation
  constants (Mehrbach et al., 1973)
• Accurate preformed alkalinity (TAº) as a
  function of inorganic to organic carbon
  decomposition

DC(t) CANT DCTdis
Difference is ascribed to the DCTdis
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Atlantic
Pacific
Indian
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Anthropogenic CO2 at the potential density 26.0
(a) and 27.3 (b)
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Inventory of CANT for 1994 106 17 Pg C
(1 Pg1015 g)
Atlantic
Indian
40 ?6 Pg
22 ?3 Pg
Pacific
44 ?5 Pg
(Sabine et al, 2004)
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Anthropogenic CO2 budget for the anthropocene
(1800-1994) and for the decades of the 1980s and
1990s (Sabine et al., 2004)
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GEOSECS 1972-1978
Total number of carbon sample locations
6,000 TCO2 estimated accuracy 15-30 µmol
kg-1 Alkalinity estimated Accuracy 21 µmol kg-1
Average Surface Water CT Increase in 2000 1.2
µmol kg-1
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Effects of CO2 enrichment on marine phytoplankton
Effect on biocalcification
Riebesell, Zondervan, Rost, Tortell, Zeebe, Morel
(2000) Nature 497, 364
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Impact on sea urchin larvaeFrom Y. Shiriyama
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Threshold temperature above which bleaching
manifests itself (1-2ºC above the long-term
summer maximum temperatures Besides they are
also affected by the pH variations
Hoegh-Guldberg (1999)
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Animal species intolerant to CO2 oscillations
Squid Illex illecebrosusLolliguncula
brevisLoligo pealei
H. Poertner
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• CONCLUSIONS
• Beneficial effect on the atmospheric CO2 uptake
  by the oceans because it mitigate the climate
  change.
• It seems that CO2 uptake is decreasing due to a
  decrease in the buffering effect by the ocean.
• Negative effect because of the oceans become more
  acid, affecting the shell-forming species.
• To obtain reliable CO2 uptake rates and global
  ocean inventory of anthropogenic CO2, good carbon
  measurements and related tracer are needed. This
  is the aim of this Summer School.

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CARBO-OCEAN Integrated Project at 5
years Coordinator C. Heinze Overall goal To
get an accurate assessment of the marine carbon
sources and sinks in the Atlantic and Southern
Oceans
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• 3 Modules
• Description
• Understanding
• Prediction
• 5 Core Themes
• Surface
• Water column
• Regional
• Feedback
• Future development

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Theme 1
Surface
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Theme 2
Water column
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Theme 3
Regional