Possible changes of delta O-18 in precipitation caused by a meltwater event in the North Atlantic

The Hamburg atmosphere general circulation model ECHAM-4 is used to investi gate how a meltwater event in the North Atlantic might alter the signal of stable water isotopes (H-2 O-18, HDO) in precipitation. Our results show th at such a meltwater event will cause significant changes in the isotopic co mposition of the precipitation over many parts of the Northern Hemisphere, but also in the tropical Atlantic region. Model simulations suggest that fo r such a scenario isotope anomalies are not only related to temperature cha nges, but also to changes in the seasonality of precipitation or the precip itation amount. A changed isotopic composition of evaporating ocean surface waters (caused by a massive meltwater input into the North Atlantic) cause s 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.