1. ANTHROPOGENIC CARBON IN THE ATLANTIC OCEAN: COMPARISON OF FIVE DATA-BASED CALCULATION METHODS Marcos Vázquez-Rodríguez 1, Franck Touratier 2, Claire Lo Monaco 3, Darryn Waugh 4, X.A. Padin 1, Richard G. J. Bellerby 5, 6, Catherine Goyet 2, Nicolas Metzl 3, Aida F. Ríos 1, Fiz F. Pérez 1 1 Instituto de Investigaciones Marinas, CSIC, Eduardo Cabello 6, E-36208 Vigo, Spain 2 BDSI, Université de Perpignan, 52 avenue Paul Alduy, Perpignan 66860, France 3 LOCEAN / IPSL, Université Pierre et Marie Curie, France 4 Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, USA 5 Bjerknes Centre for Climate Research, University of Bergen, Allégaten 55, 5007 Bergen, Norway 6 Geophysical Institute, University of Bergen, Allégaten 70, 5007 Bergen, Norway CARBOOCEAN 2 nd Annual Meeting Gran Canarias, December 4 th - 8 th

2.  Apply different methodologies to a common and recent dataset, including new data from the Arctic Ocean  Extend previous comparisons adding new methods applied at a large scale  Compare the results from five data-based methods when used to quantify the regional Anthropogenic CO 2 (C ant )  Evaluate the impact of these estimates at a inventory level AIMS OF THE STUDY

3. C ant ESTIMATION METHODS APPLIED  CFC-shortcut [Thomas and Ittekot, 2001]  TTD [Waugh et al., 2004, 2006]  TrOCA [Touratier et al., 2004, 2006]  IPSL [Lo Monaco et al., 2005]  φC T º [Vázquez-Rodríguez et al., 2006 submitted]  Results in Lee et al. (2003) using the ∆C* method [Gruber et al., 1996] have also been included for comparison.

4. Data from cruises used in calculations: - WOCE A14 (1995) - WOCE I06-Sb (1996) - NSeas (2002) - CLIVAR Repeat Section A16N (Legs 1, 2) (2003) -WOCE AR01 (1998)

5. AAIW CDW AABW NADW LSW MW

7. REGIONS OF STUDY (meridional section)

8. REGIONS OF STUDY (zonal section)

10. Specific Inventories of Anthropogenic CO 2 (mol m -2 )

11. Inventories of Anthropogenic CO 2 (Pg C)

12. θ > 5 ºC Inventories of Anthropogenic CO 2 (Pg C)

13. θ < 5 ºC

14. Inventories of Anthropogenic CO 2 (Pg C) METHODTotal Inventory (Pg C)Difference (%) ∆C* [Lee et al., 2003]47-- TTD481% TrOCA494% IPSL6539% phi-C T º5516%

15.  The latitudinal variability of the inventory trends are very similar for all five methods compared, and matches that in Lee et al. (2003) EXCEPT for the Southern Ocean (-5 Pg C lower on average).  Inventories of the θ>5 ºC layer are very similar (22-25 Pg C) but for the IPSL results (30 Pg C).  Inventories of the θ<5 ºC layer vary from 25 Pg C (TrOCA) to 36 Pg C (IPSL).  At a REGIONAL level: TTD yields the lowest inventory estimates (about -5 Pg C) for the North Atlantic equatorial and subtropical regions, mainly in the DWBC influence areas. Here, it seems to overestimate the mixing vs. advection of CFCs. TrOCA yields the lowest inventory estimates (average -4 Pg C) for the South Atlantic. φC T º tends to produce low values in the Nordic Seas. CONCLUSIONS

17. TrOCA Method [Touratier et al., 2004, 2006]

18. IPSL Method [Lo Monaco et al., 2005] C ant = C T - C bio - C T o,obs -  C o REF (1) C bio = 0.73 (O 2 o - O 2 ) + 0.5 (A T - A T o ) (2) O 2 o = O 2 sat -  k O 2 sat (3) A T o (S) = 0.0685 PO + 59.787 S - 1.448  + 217.15 (± 5.5 µmol/kg, r 2 = 0.96, n = 243) (4) A T o (N) = 42.711 S + 1.265  + 804.6 (± 9.3 µmol/kg, r 2 = 0.92, n = 297) (5) C T o,obs (S) = -0.0439 PO + 42.79 S - 12.019  + 739.83 (± 6.3 µmol/kg, r 2 = 0.99, n = 428) (6) C T o,obs (N) = 10.69 S + 0.306 NO + 1631.6 (± 9.2 µmol/kg, r 2 = 0.79, n = 364) (7)  C o REF = [C T - C bio - C T o,obs ] REF = -51 µmol/kg (8) calculated  C o REF in the North Atlantic Deep Water (NADW) detected in the South Atlantic

19. φC T º Method [Vázquez-Rodríguez et al., 2006 submitted]  C*= C T - AOU/R C - 0.5 [A T -A T o +AOU (1/R N +1/R P )] - C T  eq (2)  C dis =  C dis -  C  dis = -φ C ant / |  C dis | (3) (1)