Decadal to centennial climate variability in a model of the coupled ocean-atmosphere system

We investigate the mechanisms and predictability of climate variability on the decadal to centennial timescales using an idealized coupled ocean-atmosphere model. The ocean component is a coarse resolution (i.e., non eddy resolving) hydrostatic, primitive-equations model with greatly simplified geometry (specifically, a version of MOM), while the atmospheric component is a moist primitive-equations model with simplified parameterizations of atmospheric processes such as radiation and boundary layer transfer.

Multi-century climate simulations have been carried out both with the interactive, dynamical ocean and with a slab mixed-layer ocean model. The long-term variability of the two systems is analyzed in an attempt to identify the mechanisms and dynamics that might lead to natural climate variability at interannual to interdecadal timescales. Specifically, we investigate the timescales on which can the system be considered as truly coupled; what, if any, the role of ocean dynamics is on redenning the atmospheric response; and whether 'weather' variability in the atmosphere plays an essential role in longer term variability. The sensitivity to the poorly known parameterizations - such as the oceanic horizontal and isopycnal diffusivity - and to the effect of the ocean geometry will also be considered.