The thermal structures for the upper 500 m presented in four long meridional sections across the subantarctic and antarctic regimes of the Southern Ocean display a number of similar features as well as some differences. The similarities are associated with the latitudinal variation of depth and temperature of the temperature minimum (T min) layer and the common occurrence of much vertical relief of isotherms north of the polar front, which is believed to reflect the presence of transient features, such as meanders and eddies. The differences seem to be related to the details of the thermal structure of the polar front, the continuity of the T min layer at its northern extent, and the presence of strong thermal fronts north of the polar front. Neither local sea-air flux of heat nor the wind-induced Ekman drift is consistent with the presence of the polar front. Hence the front is not locally generated. The sea-air heat flux in the vicinity of the front reverses the large-scale trend of increased heat loss of the ocean as latitude increases: the heat flux is from ocean to atmosphere to the immediate north of the polar front and from atmosphere to ocean to the immediate south. Northward Ekman drift of surface waters is near the circumpolar maximum at the polar front, which means that the front divides the convergence region to the north from the divergence region to the south. The Antarctic Polar Front is quite similar to the Subantarctic Front of the North Pacific in nearly all respects.