• DOI:10.1023/B:JOCE.0000009600.12070.1A
• Corpus ID: 129791859

Comparison of Time-Dependent Tracer Ages in the Western North Pacific: Oceanic Background Levels of (SF6, CFC-11, CFC-12 and CFC-113

@article{Watanabe2003ComparisonOT,
  title={Comparison of Time-Dependent Tracer Ages in the Western North Pacific: Oceanic Background Levels of (SF6, CFC-11, CFC-12 and CFC-113},
  author={Yutaka W. Watanabe and Akifumi Shimamoto and Tsuneo Ono},
  journal={Journal of Oceanography},
  year={2003},
  volume={59},
  pages={719-729}
}

• Y. Watanabe, A. Shimamoto, T. Ono
• Published 1 October 2003
• Environmental Science
• Journal of Oceanography

To verify the actual usefulness of time-dependent tracer dating techniques in the ocean, we simultaneously obtained two cross sections of sulfur hexafluoride (SF6) and chlrofluoromethanes (CFC-11, trichlorofluoromethane; CFC-12, dichloro-difluromethane; CFC-113, trichlorotrifluoroethane) in the western North Pacific in 1998. The vertical distribution patterns of SF6 and CFC-113 were similar in shape to those of CFC-11 and CFC-12. Maximum penetration depths of SF6 and CFC-113 remained around 800 m in the subpolar region and 400 m in the tropical region, while the maximum penetration depths of CFC-11 and CFC-12 were still found below 1000 m depth. We also found all maximum contents of these tracers around 26.6−26.8σθ with a gradual decrease southward. This suggested that a new subsurface water mass in the subpolar region spread out over the entire North Pacific, which agrees closely with previous studies based on the salinity minimum. Moreover, we compared the tracer ages (the elapsed period of a water mass from when the water mass left from the ocean surface) using ten time-dependent tracer dating techniques, CFC-11, CFC-12, CFC-113, SF6, CFC-11/CFC-12, CFC-113/CFC-11, CFC-113/CFC-12, SF6/CFC-11, SF6/CFC-12 and SF6/CFC-113. This quantitative evaluation of multiple tracer dating techniques in the ocean was the first confirmation of its usefulness based on the observational data on the ocean basin-wide scale. We conclude that SF6/CFC-11, SF6/CFC-12, SF6/CFC-113 and SF6 dating techniques would be the most promising tools for determining the age of water mass not only just for the past several decades but for the future, too.