  The complexity of comprehensive ocean models poses an important question for
parameterisations: is there a minimum set of equations that should be
parameterised, on the one hand, to reduce the development to a minimum, and, on
the other hand, to ensure an accurate representation of large-scale flow
patterns? This work seeks to answer this to assist modern parameterisations be
more selective in their targets. For this, we considered a North Atlantic
configuration of the MIT general circulation model and studied contributions of
different model equations to the accuracy of representation of the Gulf Stream
at low resolution. Our results suggest that it is enough to parameterise only
the tracer equations for temperature and salinity and leave the other equations
in the hydrodynamic part, as well as the atmospheric model unmodified.
