Climate Response to Changes in the Meridional Energy Transport: Role of Ocean Dynamics

The climate response to inter-hemispheric unbalances in the energy budget has been the object of many recent studies. In particular, it has been repeatedly shown that the ITCZ shifts towards the hemisphere gaining energy, as the Hadley cells have to transport energy in the opposite direction.

Most of these studies, whether in aqua-planet or more realistic settings, use a slab model for the ocean, which allows to just prescribe the ocean heat transport and see the atmospheric response. However, the energy transports in the atmosphere and ocean are strongly coupled through the forcing of the ocean circulation by the surface wind.

In this study, we try to include progressively more complex (in terms of the included dynamical mechanisms) ocean models. Starting with a simple representation of Ekman transports (by the surface and return flows) in a 2-layers slab ocean, we show in an aquaplanet setting that changes in meridional heat transport by the shallow ocean tropical cells significantly reduce the response compared to cases when the atmosphere is "doing all the work".