1] The marine production, cycling, and air-sea gas ex-change of nitrous oxide (N 2 O) are simulated in a coupled climate-biogeochemical model of reduced complexity. The model gives a good representation of the large-scale features of the observed oceanic N 2 O distribution and emissions to the atmosphere. The transient behavior of the model is tested for the Younger Dryas (Y-D) cold period (12,700 – 11,550 BP), which is simulated by releasing a freshwater pulse into the North Atlantic, causing a temporary collapse of the model's Atlantic thermohaline circulation (THC). A temporary drop in atmospheric N 2 O of about 10 ppb results, while ice-core measurements show a total drop of 25 to 30 ppb. This suggests that terrestrial changes have also contributed to the observed variations. The main cause of the modeled reduction in atmospheric N 2 O is increased oceanic storage in the short-term and a reduction of new production in the long-term due to increased stratification.