How many oceans are there?
The U.S. National Oceanic and Atmospheric Administration (NOAA), identifies “one global ocean” which contains 71% of the Earth’s water. Geographically speaking, currently, five ocean basins are identified as the Pacific, Atlantic, Indian, Southern, and Arctic basins (NOAA, 2020, para.1 – 3).
Size: approx. 65.1 million sq. miles. Volume: approx. 160.7 million cu. miles. % of ocean volume: 50.1
The largest of the ocean basins, the Pacific contains more than half the world’s water and all of the continents could fit inside it. It was named by the Portuguese navigator, Ferdinand Magellan, who noted the calm (‘pacific’) waters after crossing into it in November of 1520 (NOAA, 2020, paras. 1-4).
The average depth is 4,188 meters (~14,000 ft). The Pacific’s deepest point is also the lowest known point on earth. The Mariana Trench lies 10,911 meters (~35,797 feet) below sea level (Moen, n.d., para. 4).
Size: approx. 32.9 million sq. miles. Volume: approx. 74.5 million cu. miles. % of ocean volume: 23.3
The second largest ocean basin at slightly larger than one-half the size of the Pacific. Its name derives from the Greek god, Atlas (NOAA, 2018, paras. 1-4).
Including the adjacent seas, the average depth of the Atlantic is 3,339 meters (~10,955 feet). Without the adjacent seas, the average depth is about 300 meters deeper. The deepest point in the Atlantic is the Puerto Rico Trench at 8,605 meters (~28,232 feet) (Moen, n.d., para. 4).
Size: approx. 27.2 million sq. miles. Volume: approx. 63.3 million cu. miles. % of ocean volume: 19.8
The third largest ocean basin. The present name for the Indian Ocean has been around since at least 1515 and derives from the Latin term Oceanus Orientalis Indicus, and subsequently, the country of India, which projects into it (Harper, n.d., para. 1).
The Indian Ocean averages a depth of 3,890 meters (~12,762 feet). The deepest point is the Diamantina Trench at 8,047 meters (~26,401 feet) (Moen, n.d., para. 5).
Southern (Antarctic) Ocean
Size: approx. 8.5 million sq. miles. Volume: approx. 17.2 million cu. miles. % of ocean volume: 5.4
The Southern Ocean encircles the continent of Antarctica and is shown as the area south of Latitude 60 degrees South. The average depth of the Southern Ocean is 3,270 meters (~10,700 feet) and the deepest point is 7,075 meters (~23,200 feet) (Eakins & Sharman, 2010). The deepest point lies at the southern end of the South Sandwich Trench (Moen, n.d., para. 2).
Size: approx. 6 million sq. miles. Volume: approx. 4.5 million cu. miles. % of ocean volume: 1.4
The Arctic Ocean is mostly icelocked from October to June. It’s partially covered by sea ice for most of the year and almost completely in the winter (Moen, n.d., paras. 3-4).
The average depth of the Arctic Ocean is 1,205 meters (~3,900 feet) and the greatest depth is 5,567 meters (~18,200 feet) (Eakins & Sharman, 2010).
Graphical Comparison of Size and Volume
As can be seen, either numerically or graphically, the Pacific Ocean is by far the largest body of water in terms of area covered and volume. It also holds the lowest known point on earth in the Mariana Trench. It’s worth remembering that these numbers are not static. The tectonic plates are constantly shifting and slowly changing the shape of the oceans over time as the plates (and continents) move. In millions upon millions of years, the shape and size of the oceans may be very different. Remember that NOAA only defines one global ocean. The currents and weather affect the movements of the water as it flows from one area to another. There are no definitive boundaries from one ocean basin to the next. Effectively, they are all connected.
Eakins, B.W. and Sharman, G.F. (2010). Volumes of the World’s Oceans from ETOPO1. Retrieved from https://www.ngdc.noaa.gov/mgg/global/etopo1_ocean_volumes.html.
NOAA. (2020, April 9). How many oceans are there? Retrieved from https://oceanservice.noaa.gov/facts/howmanyoceans.html.
NOAA. (2020, April 23). How did the Pacific Ocean get its name? Retrieved from https://oceanservice.noaa.gov/facts/pacific.html.
NOAA. (2018, June 25). How big is the Atlantic Ocean? Retrieved from https://oceanservice.noaa.gov/facts/atlantic.html.
Harper, D. (n.d.). Indian Ocean. In Online Etymology Dictionary. Retrieved May 6, 2020, from https://www.etymonline.com/word/Indian%20Ocean.
Moen, J. (n.d.). Arctic Ocean – Map & Details. Retrieved from https://www.worldatlas.com/aatlas/infopage/oceans/arcticocean.htm.
Moen, J. (n.d.). Atlantic Ocean – Map & Details. Retrieved from https://www.worldatlas.com/aatlas/infopage/oceans/atlanticocean.htm.
Moen, J. (n.d.). Indian Ocean – Map & Details. Retrieved from https://www.worldatlas.com/aatlas/infopage/oceans/indianocean.htm.
Moen, J. (n.d.). Pacific Ocean Map – Map of the Pacific Ocean. Retrieved from https://www.worldatlas.com/aatlas/infopage/oceans/pacificocean.htm.
Moen, J. (n.d.). Southern Ocean – Map & Details. Retrieved from https://www.worldatlas.com/aatlas/infopage/oceans/southernocean.htm.