The tracer equations as given in Section 4.2.4 require the specification of tracer fluxes through the model boundaries. Tracer fluxes through the lateral boundaries and the sea-floor are generally set to zero. The fluxes through the sea surface as heat flux, fresh water flux or radiation are maintained by turbulent processes in the atmosphere-ocean boundary layer which is not resolved by MOM. Parameterizations require input from both, such as the sea surface temperature, surface salinity, surface air temperature, humidity, and/or wind speed. MOM provides a coupling module which collects the required variables and permits the calculation of the tracer surface fluxes. This includes information which is not calculated by MOM but must be provided from a database or an atmosphere model. The relation of the surface tracer fluxes to the scheme for the calculation of the ocean model variables is given in Section 8. Simple parameterizations for the heat flux and the fresh water flux are discussed in Section 8.4.