This study explores the responses of a coupled ocean-atmosphere model to the discharge of freshwater into the North Atlantic Ocean. In the first numerical experiment in which freshwater is discharged into high North Atlantic latitudes over a period of 500 years, the thermohaline circulation (THC) in the Atlantic Ocean weakens, reducing surface air temperature over the northern North Atlantic Ocean and Greenland and, to a lesser degree, over the Arctic Ocean, the Scandinavian peninsula, and the Circumpolar Ocean and the Antarctic continent of the southern hemisphere. Upon the termination of the water discharge at the 500th year, the THC begins to intensify, regaining its original intensity in a few hundred years. With the exception of the Pacific sector of the Circumpolar Ocean of the southern hemisphere, where the surface air temperature recovery is delayed, the climate of the northern North Atlantic and surrounding regions rapidly resumes its original distribution. The evolution of the ocean-atmosphere system described above resembles the Younger Dryas event as inferred from the comprehensive analysis of ice cores and deep-sea and lake sediments. In the second experiment, in which the same amount of freshwater is discharged into the subtropical North Atlantic again over a period of 500 years, the THC and climate evolve in a manner qualitatively similar to the first experiment. However, the magnitude of the THC response is 4--5 times smaller. It appears that freshwater is much less effective in weakening the THC if it were discharged outside high North Atlantic latitudes.¿ 1997 American Geophysical Union