AN INVESTIGATION OF CLIMATE DRIFT IN A COUPLED ATMOSPHERE-OCEAN-SEA-ICE MODEL

Climate drift is a common and serious problem in most state-of-the-art coupled atmosphere-ocean-sea ice models. We consider the nature of cl imate drift in such a model, and in particular address the question of whether or not climate drift is inherent to the model, or whether the drift can be averted by a suitable choice of initial conditions or co upling procedure. The ''synchronous'' approach to coupling was adopted in which the ocean, atmosphere and sea ice models were spun-up indepe ndently to equilibrium using climatological forcing fields. The models were then coupled and integrated forward in time. Several experiments were performed which were designed to assess the impact of different coupling methodologies and changes in the initial conditions of the co mponent models on the climate drift of the system. The results of our experiments indicate that climate drift is a problem inherent to the c oupled model in that systematic errors in the components lead to incom patibilities in the surface fluxes required by the component models to maintain realistic climatologies. We conclude that climate drift can be averted only if the parameterizations of certain important physical processes are improved which should have the effect of reducing or el iminating these incompatibilities.