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UNIVERSITE DE PERPIGNAN BIOPHYSIQUE ET
DYNAMIQUE DES SYSTEMES INTEGRES
Revisited estimates of anthropogenic CO2
throughout the Atlantic Ocean a novel approach

Franck Touratier Catherine Goyet
EA 1947 BDSI, Université de Perpignan, France
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(No Transcript)
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How can we estimate anthropogenic CO2 in the
ocean?
Since anthropogenic CO2 cannot be measured at
sea, two major kinds of models have been used to
separate the anthropogenic signal from the bulk
of TCO2

• Models using back calculation techniques
• approaches of Brewer (1978), and Chen and
  Millero (1979),
• the ?C approach of Gruber et al. (1996),
• the approach of Peng et al. (1998),
• the MIX approach (Goyet et al. 1999).

• the CAO approach --------------------------------
  -----------gt

• Ocean circulation models 2.5D model of Stoecker
  et al. (1994), IPSL model (e.g. Delecluse 1994),
  MPI model (e.g. Maier-Reimer 1993), Hadley model
  (Taylor 1995), Princeton model (e.g. Sarmiento et
  al. 1995),

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A novel (back calculation) approach the CAO model
1. Definition of CAO (Carbon, Alkalinity, Oxygen
tracer)
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CARINA database
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La méthode TrOCA Tracer combining Oxygen,
iorganic Carbon, and total Alkalinity Touratier
et Goyet (a,b 2004)
? quasi-conservatif
? conservatif
? TrOCA0 is the unknown of the system
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• The form of the equation CAO0 ƒ (?) is first
  determined by using the program of e.g. Lewis and
  Wallace (1998). The best fit is obtained with an
  exponential of the form a e-?/b (r2 1).

• The coefficients a and b are then determined by
  fitting the exponential function to CAO0 values
  computed from recent TCO2, TA, and O2 data
  sampled in waters from the latitude belt
  20S-40S, and characterized by ? 2C.

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3. Precision of the CAO model
Prior 1991 During /after 1991
?TCO2 15 µmol kg-1 2 µmol kg-1
?TA 15 µmol kg-1 4 µmol kg-1
?O2 1.1 µmol kg-1 1.1 µmol kg-1
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4. Results for the 1990s
?North-south section
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?East-west sections
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5. Results for the 1980s
?North-south section
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6. Anthropogenic CO2 inventories for the 1980s
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7. Inventories for the 1980s and the 1990s
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8. Net increase of anthropogenic CO2 for the
period 1984-1995
?The annual rate 0.47 0.02 Gt C yr-1
0.66 Gt C yr-1
?
?
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Perspectives

• We are planning to use the CAO model to estimate
  the concentrations of anthropogenic CO2 in other
  oceanic regions (Indian Ocean, Pacific Ocean),

• Using exactly the same observations to estimate
  the anthropogenic CO2, it would be useful to
  compare the results of the different models. The
  paper of Coatanoan et al. (2001), that compares
  the MIX and the ?C approaches using data from
  the WOCE section I1 (northern Indian Ocean),
  shows that information can be gained from this
  kind of inter-comparison exercise.

The end