In an analytical study the stability of the thermohaline circulation with respect to freshwater perturbations in high latitudes is investigated. The study is based on a coupled ocean and atmosphere box model in an idealized North Atlantic geometry. The box model provides a qualitative understanding of how the thermohaline circulation is affected by feedback mechanisms associated with changes in atmospheric transports of heat and moisture. Within a linear analysis we examine the stability of the thermohaline circulation for a range of different atmospheric boundary conditions. The stability of the coupled system depends on the imposed transport parameterizations and the basic state. For the underlying non-linear system we examine the sensitivity with respect to the strength of salinity perturbation.