What is it meant by world ocean?

Answer 1

World or global ocean basically means the combination of the Atlantic, Pacific, Indian, Arctic and Southern Oceans and Mediterranean Sea. From the south pole of Earth, the Atlantic, Indian, and Pacific Oceans can be viewed as lobes that extend northward from the Southern Ocean while the Atlantic extends into the Mediterranean Sea through the Strait of Gibraltar as well as extending into the Arctic Ocean around Greenland and is also connected to the Pacific Ocean by the Bering Strait between Alaska and the extreme east of Russia. The Atlantic Ocean extends into the Indian Ocean around Cape of Good Hope and Cape Agulhas in southern Africa and into the Pacific Ocean around Cape Horn in southernmost America.

So these links and extensions form a continuous expanse of water accessible to shipping, although continental drift throughout the history of Earth has continually changed the precise demarcation and structure of world ocean.

The term "world ocean" to designate this unity and continuity apparently originated in a series of lectures given by a Soviet oceanographger called Yuly Mikhailovich Shokalsky studying the link between meteorology and hydrology in 1917 first used this term to designate the interconnection of the planet's marine waters, that thereby comprise the bulk of the hydrosphere, and cover more than 70% of the Earth's surface.