I got curious, because it had always been the Antarctic Ocean to me. Seems Southern won by a vote of 18 to 10 among member nations in 2000 at the International Hydrographic Organization. I even didn't know there was another name. But I live much closer to the Northern Ocean, so maybe I was over-influenced by the pattern.
FWIW, both Apple and Google Maps have 7: Arctic Ocean, Indian Ocean, North Atlantic Ocean, North Pacific Ocean, South Atlantic Ocean, South Pacific Ocean, and Southern Ocean.