Climate model simulations are used to demonstrate that there is not a simple link between the mechanical energy supply and heat transport in the Atlantic. Setting the flux of momentum into the ocean to zero between 35--60¿S reduces the net mechanical energy input by more than a factor of two without much effect on the heat transport in the Atlantic. The strong westerly winds in the Southern Ocean are found to be more important for the circulation of bottom water and for localizing the upwelling of deep water around Antarctica. Furthermore, it is illustrated that the hydrological cycle plays a significant role in maintaining the global ocean circulation and the associated heat transport in the Atlantic, given sufficient mechanical energy to support the diapycnal mixing. A reduction of the meridional moisture transport to the Southern Ocean by a factor of two reduces heat transport in the Atlantic by about the same factor.