Sensitivity of a coarse resolution ocean general circulation model under climate change forcing

Tunable parameters in an ocean general circulation model are assessed as modifiers to the model response to several climate change scenarios. For the current climate scenario it is found that vertical diffusivity plays a dominant roˆ le as expected. An analysis of the horizontal diffusivity variation suggests that use of the peak value of the overturning streamfunction is a misleading indicator of model flow strength. For the warming and cooling scenarios vertical and horizontal diffusivity variations dominated the equilibria response. However, these tunable parameters are of minor significance in the transient response in the cooling scenarios. The diffusively dominant warming scenarios, in contrast, very much depend on the magnitude of the vertical diffusivity. This has important implications for the use of coarse resolution models in coupled atmosphereocean model climate change simulations.