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Revisited estimates of anthropogenic CO 2 throughout the Atlantic Ocean: a novel approach

UNIVERSITE DE PERPIGNAN BIOPHYSIQUE ET DYNAMIQUE DES SYSTEMES INTEGRES. EA: 1947. BDSI. Revisited estimates of anthropogenic CO 2 throughout the Atlantic Ocean: a novel approach. Franck Touratier & Catherine Goyet. EA 1947 BDSI, Université de Perpignan, France.

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Revisited estimates of anthropogenic CO 2 throughout the Atlantic Ocean: a novel approach

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  1. UNIVERSITE DE PERPIGNAN BIOPHYSIQUE ET DYNAMIQUE DES SYSTEMES INTEGRES EA: 1947 BDSI Revisited estimates of anthropogenic CO2 throughout the Atlantic Ocean: a novel approach Franck Touratier & Catherine Goyet EA 1947 BDSI, Université de Perpignan, France

  2. 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 -------------------------------------------> • 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), …

  3. A novel (back calculation) approach: the CAO model 1. Definition of CAO (Carbon, Alkalinity, Oxygen tracer):

  4. CARINA database

  5. La méthode TrOCA Tracer combining Oxygen, iorganic Carbon, and total Alkalinity Touratier et Goyet (a,b; 2004)  ‘quasi-conservatif’  ‘conservatif’  TrOCA0is the unknown of the system

  6. 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 20°S-40°S, and characterized by  ≤ 2°C.

  7. 3. Precision of the CAO model

  8. 4. Results for the 1990s North-south section

  9. East-west sections

  10. 5. Results for the 1980s North-south section

  11. 6. Anthropogenic CO2 inventories for the 1980s

  12. 7. Inventories for the 1980s and the 1990s

  13. 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 ? ?

  14. 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

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