As the only major ocean basin that allows for circumpolar flow, with no continental boundaries against which zonal pressure gradients may be established, the Southern Ocean has been singled out as a region in which transient mesoscale eddies are especially important. There we’re taught that the transient eddies do what the temporal mean flow cannot, delivering heat poleward, just as atmospheric storm systems do at the mid-latitudes of the atmosphere.
Recent evidence indicates the role of transient eddies to be more subtle. Topographically fixed meanders in the flow, which may be referred to as stationary waves or standing eddies, in fact deliver much of the poleward heat transport. Together, the transient and standing eddies deliver enough poleward heat transport to more than fully compensate for the equatorward heat transport forced by prevailing westerly winds. In models, we see that the standing eddy heat transport intensifies at higher resolution, becoming dominant even as the field of transient eddies becomes more fully resolved.