Dansgaard–Oeschger Oscillations in a Coupled Atmosphere–Ocean Climate Model

Abstract

Abstract A reduced model of the global thermohaline circulation has been asynchronously coupled to a simple energy balance climate model in order to investigate the natural variability of the overturning circulation that may have been characteristic of late glacial conditions. Previous analyses with the ocean-only component of the model have suggested that the nature of the internal variability of the thermohaline circulation was a strong function of the surface boundary conditions on temperature and salinity flux. When the boundary conditions were altered from those corresponding to modern conditions to those appropriate to full glacial conditions, then the internal variability was shown to be radically transformed. Under modern conditions the ocean-only version of the model delivered an overturning circulation that was only weakly time dependent with a characteristic period of centuries. Under full glacial boundary conditions, however, the circulation became strongly time dependent with a characteristic...