Background: A spring 2000 decision by the International Hydrographic Organization delimited a fifth world ocean from the southern portions of the Atlantic Ocean, Indian Ocean, and Pacific Ocean. The new ocean extends from the coast of Antarctica north to 60 degrees south latitude which coincides with the Antarctic Treaty Limit. The Atlantic Ocean remains the second-largest of the world's five oceans (after the Pacific Ocean, but larger than the Indian Ocean, Southern Ocean, and Arctic Ocean).