While there is one global interconnected ocean, this massive body of water surrounding all land masses on Earth can be further subdivided based on historical, geographic, and cultural factors.
Oceans cover much of the Earth’s surface. About 71% of the Earth’s surface is covered by oceans and 97% of all the water found on Earth is in the ocean. To put it in numbers, 321,003,271 cubic miles of water are found in the ocean, which according to NOAA, can fill about 352,670,000,000,000,000,000 gallon-sized milk containers.
Why are Oceans Important?
Aside from being a huge body of water, oceans are important to the health of the Earth for many reasons. Oceans produce half of the oxygen that reaches the atmosphere and are a carbon sink, absorbing massive amounts of carbon dioxide. In other words, the world’s oceans are a huge carbon reservoir, hold more than 50 times the carbon dioxide compared to the atmosphere.
Oceans also move heat around the world, helping to regulate the world’s climate. Warm ocean currents move towards the poles, cool, and then return back towards the equator. This constant mixing of temperatures affects global weather patterns. (Related: How Ocean Currents Move Pollution Around the World)
The Number of Oceans Depends on How You Count Them
The number of oceans in the world depends on the perspective. The designation of the world’s oceans has evolved over time.
One Global Ocean
There is one global ocean. All ocean waters are connected. The world ocean covers 71% of the Earth’s surface.
Are There 3, 4, or 5 Oceans in the World?
On Earth, there are three major oceans: the Pacific, Atlantic, and Indian oceans.
Historically, there are four ocean basins that include the three major oceans (Pacific, Atlantic, and Indian) and the Arctic Ocean. There are five oceans if you also include the Southern Ocean as a separate ocean.
The Southern Ocean is a fairly recently named addition (2000) that is not universally recognized by all countries and organizations and has yet to be ratified by the international community.
The video below explains the names and boundaries of the world’s oceans based on one global ocean, the three major oceans, the four historic oceans, and the five world oceans.
The Five World Oceans
Each of the five world oceans are described here including the size of each ocean as well as a map showing the location and boundaries for each ocean.
The Pacific Ocean is the world’s largest ocean. It spans from the Arctic Ocean in the north to the Southern Ocean in the south.
The Pacific Ocean is 165,250,000 square km (63,800,000 sq. mi) in area and covers 46% of Earth’s water surface.
The Pacific Ocean covers 28% of the global surface which is roughly equivalent to all of the landmasses combined.
The deepest point on Earth, the Mariana Trench, is located in the Pacific Ocean.
The Pacific Ocean includes the Bali Sea, Bering Sea, Bering Strait, Coral Sea, East China Sea, Gulf of Alaska, Gulf of Tonkin, Philippine Sea, Sea of Japan, Sea of Okhotsk, South China Sea, Tasman Sea, and other tributary water bodies.
This is the second largest ocean in the World. This body of water is located between Africa, Europe, the Arctic Ocean, the Americas, and the Southern Ocean.
The area of the Atlantic Ocean is about 106,460,000 square km (41,100,000 sq mi).
The lowest point in the Atlantic Ocean is the Milwaukee Deep in the Puerto Rico Trench with a depth of 8,376 m (27,480 ft).
The Atlantic Ocean includes the Baltic Sea, Black Sea, Caribbean Sea, Davis Strait, Denmark Strait, part of the Drake Passage, Gulf of Mexico, Labrador Sea, Mediterranean Sea, North Sea, Norwegian Sea, almost all of the Scotia Sea, and other tributary water bodies.
The Atlantic Ocean is found along the eastern coast of the United States, the eastern coast of South America, the western coast of Africa, and north and western Europe.
The Indian Ocean is the third largest ocean. This body of water stretches between Africa, the Southern Ocean, Asia, and Australia.
The area of the Indian Ocean is 70,560,000 sq km (27,240,000 sq mi) which represents 19.8% of the water on Earth’s surface.
The Indian Ocean includes includes Andaman Sea, Arabian Sea, Bay of Bengal, Flores Sea, Great Australian Bight, Gulf of Aden, Gulf of Oman, Java Sea, Mozambique Channel, Persian Gulf, Red Sea, Savu Sea, Strait of Malacca, Timor Sea, and other tributary water bodies.
The Indian Ocean is found along the eastern coast of Africa, the Middle East, the southern part of Asia, and the western coast of Australia.
The Arctic Ocean:
The Arctic Ocean is the smallest ocean. The area of the Arctic Ocean is 14,056,000 sq km (5,427,000 sq mi) which makes it the only ocean smaller than Russia.
This ocean is also the coldest of the world’s oceans.
Found mostly north of the Arctic Circle, this ocean lies between Europe, Asia, and North America.
The Arctic Ocean includes Baffin Bay, Barents Sea, Beaufort Sea, Chukchi Sea, East Siberian Sea, Greenland Sea, Hudson Bay, Hudson Strait, Kara Sea, Laptev Sea, Northwest Passage, and other tributary water bodies.
The Southern Ocean is a proposed ocean surrounding Antarctica with a northern limit of 60°S. The northern boundary abuts the Atlantic, Indian and Pacific Oceans, making it the only ocean not to have a land mass as the border.
What makes some organizations designate the Southern Ocean as an ocean is the fact that its waters differ from other oceans due to fairly rapid circulation.
It is the second smallest of the five world oceans. It has an area of 20.327 million sq km (7.849 million sq mi).
The Southern Ocean includes Amundsen Sea, Bellingshausen Sea, part of the Drake Passage, Ross Sea, a small part of the Scotia Sea, Weddell Sea, and other tributary water bodies.
How are the Ocean Borders and Names Determined?
The International Hydrographic Organization (IHO), which first convened in 1919 (and was originally referred to as the International Hydrographic Bureau (IHB)), is the inter-governmental organization that creates the international agreement of ocean borders and names.
The outcomes of each convention are published in the Limits of Oceans and Seas.
Watch: How many oceans are there?
IHO (International Hydrographic Organization), 2000. Report of the International Hydrographic Organisation. Working Paper No. 57 (WP 57). 20th Session of the United Nations Group of Experts on Geographical Names, (New York), 17–28 January 2000.