A simple way to model stratification of the ocean or atmosphere is in terms of two superposed homogeneous layers of different density. Effects of cooling of the upper layer, such as that which occurs during bottom-water formation in the ocean, can be simulated by mass transfer from the upper layer to the lower layer. A model is constructed to see What effect such a mass transfer has on the flow when the mass transfer is confined to a limited region. The main effects are (i) doming of the interface, which maintains pressure gradients in balance with the velocity field, (ii) cyclonic rotation in the upper layer due to conservation of angular momentum of particles king drawn toward the sink, yet anticyclonic vorticity for those particles outside the mass transfer region due to shrinking of vortex lines drawn up over the dome. (iii) generally anticyclonic rotation in the lower layer due to particles tending to maintain their angular momentum while being pushed outwards, but some cyclonic rotation near the centre of mass transfer, due to momentum transfer from the upper layer. Similar effects to these are seen in the Greenland Sea where bottom water formation occurs. Results of the same sort are also found in a laboratory model of the process.