Meridional energy transport in the atmosphere-ocean system: theory and simulation

We will present and numerically test various theoretical and scaling arguments for the magnitude of the meridional energy transport in the atmosphere-ocean system, and its partitioning between atmosphere and ocean.

The oceanic energy transport exceeds that of the atmosphere at very low latitudes, but the converse holds at mid and high latitudes. We discuss the underlying reasons for this, noting that with higher values of diapycnal diffusivity the oceanic energy transport could, in principle, dominate everywhere. The oceanic energy transport in the Southern Hemisphere is smaller than that in the Northern Hemisphere, and this is primarily because of a partial cancellation between a wind-driven deep circulation, enabled by a southern hemisphere circumpolar channel, and a diffusively-controlled deep circulation. We suggest that energy transport associated with the ocean's wind-driven ocean gyres will scale with external parameters in approximately the same way as that of the mid-latitude atmosphere so that, for example, the heat transports of both systems will increase in the same way with the pole--equator temperature gradient. On the other hand, the deep circulation of the ocean is not so tightly coupled with the atmosphere and its energy transport scales in a quite different fashion, increasing much more slowly with meridional temperature gradient, and allowing the atmosphere to potentially compensate for changes in the ocean circulation. These ideas and the associated scalings are all tested using a simply-configured coupled primitive equation atmosphere-ocean mode and the results presented.