TRANSIENT-RESPONSE OF THE HADLEY-CENTER COUPLED OCEAN-ATMOSPHERE MODEL TO INCREASING CARBON-DIOXIDE .1. CONTROL CLIMATE AND FLUX ADJUSTMENT

This paper describes the initialization of an experiment to study the time-dependent response of a high-resolution global coupled ocean-atmo sphere general circulation model to a gradual increase in carbon dioxi de. The stability of the control integration with respect to climate d rift is assessed, and aspects of the model climatology relevant to the simulation of climate change are discussed. The observed variation of oceanic temperature with latitude and depth is basically well simulat ed, although, in common with other ocean models, the main thermocline is too diffuse. Nevertheless, it is found that large heat and water fl ux adjustments must be added to the surface layer of the ocean in orde r to prevent the occurrence of unacceptable climate drift. The ocean m odel appears to achieve insufficient meridional heat transport, and th is is supported by the pattern of the heat flux adjustment term, altho ugh errors in the simulated atmosphere-ocean heat flux also contribute to the latter. The application of the flux adjustments restricts clim ate drift during the 75-year control experiment. However, a gradual wa rming still occurs in the surface layers of the Southern Ocean because the flux adjustments are inserted as additive terms in this integrati on and cannot therefore be guaranteed to prevent climate drift complet ely.