Carbon tetrachloride and chlorofluorocarbons in the South Atlantic Ocean, 19°S

• Published in: Journal of Geophysical Research
• Main Authors: Wallace, Douglas W.R., Putzka, A., Beining, P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 1994
• Subjects: Antarctic; Antarc*; North Atlantic Deep Water; North Atlantic; South Atlantic Ocean
• Online Access: https://oceanrep.geomar.de/id/eprint/153/; https://oceanrep.geomar.de/id/eprint/153/1/Wallace%281994%29.pdf; https://doi.org/10.1029/94JC00031

Exploratory measurements of a suite of anthropogenic halocarbon compounds (CCl4, CCl2FCClF2 (CFC-113), CH3CCl3, CCl3F (CFC-11)) were made using a new analytical technique on RV Meteor cruise 15 along 19°S (World Ocean Circulation Experiment (WOCE) Line A9)) in the Atlantic Ocean during February–March 1991. A separate analytical system was used to determine CCl2F2 (CFC-12) and CCl3F (CFC-11). A limited number of CFC-113 profiles indicated that it was undetectable below 400–500 m. The CCl4 data indicate that the entire Brazil Basin contains readily measurable levels of CCl4 (>0.05 pmol kg−1), whereas the deep Angola Basin contains very low levels (≤0.02 pmol kg−1). Slightly higher levels were found close to the bottom in the deep Angola Basin: possibly an anthropogenic signature. In contrast, most of the deep Brazil Basin and all of the deep Angola Basin (>1000 m) had undetectable levels of CFC-11, CFC-12, and CFC-113. Preindustrial levels of CCl4 in the atmosphere were therefore negligible (atmospheric mixing ratio <0.1 pptv). CCl4/CFC-11 ratios are used to estimate apparent ages and dilution factors for the North Atlantic Deep Water and Antarctic Bottom Water. Whereas CCl4/CFC-11/CFC-12 levels are internally consistent in deep waters, suggesting near-conservative behavior, there is evidence for very rapid removal of CCl4 in the thermocline. Removal rates suggest that in addition to neutral hydrolysis, some other loss pathway must be involved.