Initial conditions for this problem are a quiescent free surface and velocity field, and no stratification.
Stratification can be turned off by setting beta to zero in suntans.dat. This is because the equation
of state, as given in suntans/main/state.c is linear and only requires beta to convert from
salinity to density. Note that when beta is zero, advection of salinity is also not computed, which can
save on computation time.