>>10874229Chlorofluorocarbons (CFCs) are anthropogenic compounds that have been released into the atmosphere since the 1930s in various applications such as in air-conditioning, refrigeration, blowing agents in foams, insulations and packing materials, propellants in aerosol cans, and as solvents.[36] The entry of CFCs into the ocean makes them extremely useful as transient tracers to estimate rates and pathways of ocean circulation and mixing processes.[37] However, due to production restrictions of CFCs in the 1980s, atmospheric concentrations of CFC-11 and CFC-12 has stopped increasing, and the CFC-11 to CFC-12 ratio in the atmosphere have been steadily decreasing, making water dating of water masses more problematic.[37] Incidentally, production and release of sulfur hexafluoride (SF6) have rapidly increased in the atmosphere since the 1970s.[37] Similar to CFCs, SF6 is also an inert gas and is not affected by oceanic chemical or biological activities.[38] Thus, using CFCs in concert with SF6 as a tracer resolves the water dating issues due to decreased CFC concentrations.
