Carbon dioxide along WOCE line A14: Water masses characterization and anthropogenic entry

• Published in: Journal of Geophysical Research
• Main Authors: Ríos, A. F., Álvarez-Salgado, X. A., Pérez, F. F., Bingler, L. S., Arístegui, J., Mémery, Laurent
• Other Authors: Laboratoire d'océanographie dynamique et de climatologie (LODYC), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2003
• Subjects: Oceanography: Biological and Chemical: Carbon cycling; Oceanography: General: Water masses; Oceanography: General: Descriptive and regional oceanography; Oceanography: Physical: Hydrography; CO 2; anthropogenic carbon; water masses; South Atlantic; Earth Science; [SDU]Sciences of the Universe [physics]; Antarctic; Austral; Mid-Atlantic Ridge; Scripps; Antarc*; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://hal.science/hal-04110038; https://doi.org/10.1029/2000JC000366

International audience The meridional WOCE line A14, just east of the South Atlantic Mid-Atlantic Ridge, was surveyed during the austral summer of 1995 from 4°N to 45°S. Full-depth profiles of pH, total alkalinity (TA), and total inorganic carbon (C T ) were measured, allowing a test of the internal consistency of the CO 2 system parameters. The correlation between C T measured and calculated from pH and TA was very good (r 2 = 0.998), with an insignificant average difference of 0.1 ± 3.0 μmol kg -1 (n = 964 data). CO 2 certified reference materials (CRMs) and a collection of selected samples subsequently analyzed at the Scripps Institution of Oceanography were used to assess the accuracy of our measurements at sea with satisfactory results. The three measured CO 2 system variables were then used to identify the characteristic array of zonal flows throughout the South Atlantic intersected by A14. Equatorial, subequatorial, subtropical, and subantarctic domains were identified at the depth range of the surface water, South Atlantic Central Water (SACW), Antarctic Intermediate Water (AAIW), Upper Circumpolar Water (UCPW), North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW). The nonconservative CO 2 system parameters (pH, TA, C T ) have been useful in identifying the transition from aged subequatorial to ventilated subtropical surface, central and intermediate waters. They have been identified as good tracers of the zonal circulation of NADW, with marked flows at the equator, 13°S, and 22°S (the "Namib Col Current") and the sharp transition from UNADW to UCPW at 23°S. The anthropogenic CO 2 inventory (C ANT ) was estimated and compared with CFC-derived apparent ages for different water masses along A14. The anthropogenic entry reached maximum in the relatively young and ventilated subantarctic and subtropical domains where AAIW was the most efficient CO 2 trap. The calculated annual rate of C ANT entry by AAIW was 0.82 μmol kg -1 y -1 , in agreement with the annual rate estimated from the ...