Tracers
The tracers to be advected around can be specified via a list of symbols. By default the model evolves temperature and salinity
tracers = (:T, :S)but any number of arbitrary tracers can be appended to this list. For example, to evolve quantities $C_1$, CO₂, and nitrogen as passive tracers you could set them up as
tracers = (:T, :S, :C₁, :CO₂, :nitrogen)An active tracer typically denotes a tracer quantity that affects the fluid dynamics through buoyancy. In the ocean temperature and salinity are active tracers. Passive tracers, on the other hand, typically do not affect the fluid dynamics are are passively advected around by the flow field.