Climate change in an idealized coupled general circulation model

We present the results of climate change simulations with an idealized coupled ocean-atmosphere climate model. The coupled model is simplified in many respects: there are no ocean boundaries, clouds, or sea ice, but the primitive equations of motion and an active hydrological cycle are retained. We examine how atmosphere and ocean energy transports respond to changes in climate owing to changes in the optical thickness of a longwave absorber (representing greenhouse gases). In low-latitudes, existing arguments for the relationship between energy and mass transport (the 'gross stability') do not account for the simulation results. In high-latitudes, ocean heat transport is small; in spite of this, the coupled simulations can have different mean surface air temperature and amounts of polar amplification compared with corresponding atmosphere-only simulations. Atmosphere sensible and latent heat fluxes as well as ocean heat fluxes change with climate, and strongly for large climate changes, without there necessarily being approximate compensation among the individual changes.