Harnessing of the Transients of Anthropogenic Halogenated Compounds for Understanding Ocean Processes: Critical Steps, Lessons Learned and Ways Forward

Measurement of the global distribution of a suite of stable, volatile, anthropogenic halogenated compounds in the ocean over the past 40 years has contributed to major improvements in identifying, understanding and modelling ocean circulation pathways as well as biogeochemical processes such as anthropogenic CO₂ uptake. At a time when the oceanographic community is considering the potential of several new technologies and observational approaches (e.g. sensors, autonomous systems and omics), we will review the scientific origins of these impactful tracers and the challenges and approaches associated with assembly of a high-quality data set covering the global ocean.

The presentation will highlight how global measurements of compounds such as the CFCs and SF₆ progressed via: (1) adaptation and development of analytical methods by a small number of research groups in the early 1980’s; (2) pioneering measurements where challenges of data collection were overcome and where the potential of the tracers was demonstrated; (3) development and propagation of standards and robust analytical methods; (4) intercomparisons and expansion of measurement capability worldwide to allow sampling of the global ocean while maintaining data quality; (5) research that provided key supporting information required to interpret the dataset; (6) the generation of quality-controlled, global datasets; (7) development of approaches to extract quantitative information from the measured distributions.

Key contributions will be identified and the history, and especially challenges and lessons learned will be reviewed in the context of emerging, international ocean data collection efforts of today. We will conclude with our views of opportunities and requirements for continued use of this class of tracer to address the scientific challenges of the future.