Transient Tracer

A transient tracer is a substance with a known, time-varying input to the ocean, used to date water masses and quantify ventilation rates. The classic examples are the chlorofluorocarbons CFC-11 and CFC-12, SF6, bomb-produced tritium and its decay product helium-3, and bomb radiocarbon, all injected into the surface ocean over the twentieth century. Because the atmospheric history is known, the interior concentration fixes the time since a parcel last touched the surface. Transient tracers measured along WOCE and GO-SHIP sections map deep and intermediate water formation and the penetration depth of anthropogenic carbon.