A two-compartment model of Prince William Sound (PWS), Alaska, is developed. One compartment, corresponding to the southern PWS, represents advective phenomena, while the other is dominated by diffusion. This simple model is shown to reproduce rather well the temporal evolution of the mass of a passive tracer contained in PWS simulated by a complex, three-dimensional model under five types of surface forcing. The three parameters of the box-model have clear physical meanings, which helps to understand the hydrodynamics of PWS. In particular, the fraction of the flow entering the northern PWS is estimated, as well as the turnover time of the two regions considered
