The Hamburg atmosphere general circulation model ECHAM-4 is used to investigate how a meltwater event in the North Atlantic might alter the signal of stable water isotopes (H2 18O,HDO) in precipitation. Our results show that such a meltwater event will cause significant changes in the isotopic composition of the precipitation over many parts of the Northern Hemisphere, but also in the tropical Atlantic region. Model simulations suggest that for such a scenario isotope anomalies are not only related to temperature changes, but also to changes in the seasonality of precipitation or the precipitation amount. A changed isotopic composition of evaporating ocean surface waters (caused by a massive meltwater input into the North Atlantic) causes temperature-independent isotope anomalies, too. Changes of the deuterium excess are even more affected by the imposed oceanic isotope anomaly due to the nonlinearity of the evaporation process. ¿ 2000 American Geophysical Union