With a simplified two-dimensional Atlantic Ocean model, we investigate the response of the deep ocean circulation to reconstructed sea surface salinity and temperature used as surface boundary conditions at two time slices: just before and during Heinrich event 4. In contrast to previous studies, we do not make any assumption about freshwater input. Our model results suggest that the recorded estimations of surface hydrological changes during an Heinrich event are able to induce a drastic slowdown, or even a collapse, of the overall Atlantic thermohaline circulation. This is, to some extent, consistent with records of the deep sea ventilation at these times. ¿ 1999 American Geophysical Union