Dansgaard-Oeschger events in a box ocean model

A generic nine-box ocean model (GNOM) is developed to study the stability and variability of the Atlantic Meridional Overturning Circulation (AMOC). Using this model, it is shown that centennial to millennial time scale self-sustained oscillations in AMOC strength and associated climate characteristics resembling temporal dynamics of observed Dansgaard-Oeschger events appear within a certain range of the boundary conditions (temperature and freshwater flux). Adding white noise to the system makes such oscillations more robust, i.e. they occur within a larger area in the phase space of temperature-freshwater forcing. However, regardless of the model’s parameters and boundary conditions, the typical periodicity of such oscillations is about 1000 years, which is much shorter than the typical recurrence time of observed  Dansgaard-Oeschger events. Only after adding an interaction with an additional component, which has a longer internal time scale and mimics the response of the surrounding ice sheets, do much longer self-sustained oscillations of AMOC arise.