The Oceans and Seas in the World

Up until recently, most countries and organizations only recognized four ocean basins. While there is really only one global ocean that covers 71% of the earth, there are now five distinct regions and the boundaries between them have changed over human history. The five named oceans are the Atlantic, Pacific, Indian, Arctic, and Southern, with Southern being the newest. In addition to these ocean areas, there are more than 50 seas around the world. Seas are a part of oceans but are partially or almost fully enclosed by land.

Because the ocean covers a significant portion of the planet, it’s an incredibly important part and life as we know it is dependent on the health of the oceans and seas. Home to millions of animals, the ocean provides a range of ecosystems and habitats like coral reefs, kelp forest, and the ocean floor.

Atlantic Ocean

As the second largest ocean, the Atlantic stretches from the Arctic Circle to the Southern Ocean. It’s bordered by the Americas to the west and Europe/Africa to the east and is 29,637,900 square miles. This ocean includes the Baltic Sea, Black Sea, Gulf of Mexico, and the North Sea and the location between the American, Europeans, and African continents has made it an important avenue of trade and travel. Unfortunately, one such triangular trade route in history was particularly cruel, as the Trans-Atlantic Slave Trade lasted for 366 years and brought 12.5 million Africans across the ocean.

The North Atlantic right whale is one animal that calls the Atlantic home but it’s currently heading toward extinction and only ~400 are left in the wild. Ship strikes and environmental stress have contributed to this species’ decline.

Arctic Ocean

As the world’s smallest and northernmost ocean, the Arctic is found around the Artic Circle and between Europe, Asia, and North America. This ocean might have the smallest square miles (6.1 million square miles) but is one of the most critical and visibly disturbed regions when it comes to climate change. The Arctic and the people and animals that call it home are dealing with rising temperatures on a drastically different level than the rest of the world.

The US, Canada, Iceland, Greenland, Norway, and Russia all have territories in or around this ocean and all have tried to lay claim to the oil found deep beneath Arctic land and water. Deep sea drilling would be a catastrophe to an already at risk ecosystem, as oil spills and habitat destruction go hand in hand with any oil drilling. And in addition to oil and gas, the Artic also provides a path for shipping lanes and a military presence.

Indian Ocean

Located between Africa, the Southern Ocean, Asia, and Australia, the Indian Ocean is the third largest ocean and known for causing the monsoonal weather patterns that dominate much of southeast Asia for part of the year. The Indian Ocean has four important waterways, including the Suez Canal that was recently blocked.

There are many animals and plants that call this ocean home, including sea turtles, manta rays, reef sharks, and humpback whales. While tortoises live on land, the largest population of endangered Aldabra giant tortoise calls the Aldabra Atoll in the Seychelles/Indian Ocean home. The Indian Ocean is also home to important migration paths for many marine animals, including one tiger shark that managed to make a 4,000 mile trek across the Indian Ocean.

Additionally, there are many gorgeous islands and atolls in the Indian Ocean that help support the biodiversity of the ocean. However, even the most remote places are seeing the effects of climate change. The Seychelles, located in the Indian Ocean about 1,000 miles east of Kenya and 700 miles northeast of Madagascar, consist of two major island groups with more than 110 islands. Back in 2010, it was reported that the Seychelles were seeing the world’s worst coral die off and some thought that rising sea levels would put most of this island nation underwater in 50-100 years.

In 1998 and 2016, a significant amount of the coral reefs around these islands faced an environmental event called bleaching. This event happens when warming waters cause coral to expel the colorful algae in their skeletons and eventually starve. Coral nurseries have been launched by conservationists to help nurture and transplant coral fragments back to the reefs around the Seychelles.

This tiny island nation isn’t the only place in the Indian Ocean facing threats from climate change. Located 1,000 miles east of the Seychelles, the Chagos Archipelago in the Indian Ocean are home to coral reefs that have been largely undisturbed by humans for the last 50 years. Back in 2010, this archipelago was designated as a Marine Protected Area and became one of the largest marine reserves in the world.

Pacific Ocean

This ocean, found in the Western Hemisphere and between Asia and the Americas, is the world’s largest and is 60,060,700 square miles. It actually covers 28% of the Earth and is even equal to almost all of Earth’s land area. The deepest point of the Pacific is also the deepest point in the world, the Challenger Deep in the Mariana Trench. In addition to the Challenger Deep, this ocean is home to many islands, coral reefs, wildlife, and more. From the islands off Alaska to Channel Island off California to the Hawaiian Islands to the Pacific Islands, there are numerous islands in the world’s biggest ocean that are home to a variety of people, cultures, wildlife, and plants.

Unfortunately, the Pacific Ocean is also home to a man made structure that is called the ‘Great Pacific Garbage Patch’. This floating pile of trash is the largest and most famous of its kind, as it’s larger than the state of Texas. Discovered in 1997, the patch now contains roughly 79,000 metric tons of plastic, with most being microplastics and abandoned fishing gear. In fact, fishing nets are an estimated 46% of the patch and the microplastics make the patch look less like an island of floating trash and more like a cloudy soup.

Southern Ocean

As the newly recognized ocean, the Southern Ocean surrounds Antarctica and stretches out to 60 degrees south latitude. It is the fourth largest ocean with 7,848,300 square miles but is home to the largest ocean current, the 13,049 mile Antarctic Circumpolar Current. This current moves 130 million cubic meters of water a second, which is more than any river in the world.

Despite its remote and cold climate, the Southern Ocean is home to a variety of animals and plants and rich phytoplankton from the Antarctic Convergence helps feed a majority of animals in the area. Penguins, like emperor, adelie, Gentoo, Homboldt, and king penguins all call the Antarctic home at various parts of the year and other marine life in the ocean includes whales, sharks, orcas, seals, squid, false killer whales, and birds like albatross and terns.

The World’s Seas

While many might use ‘sea’ and ‘ocean’ interchangeably, there is a technical difference between the two. Seas are a division of the ocean that are enclosed or partly enclosed by land and there are more than 50 on earth. The three major sea types include hypersaline lakes, nearly enclosed seas, and partly enclosed seas. There are plenty of seas in the world, like the Red Sea, the Mediterranean Sea, and the Arabian Sea, but my personal favorite is the Salish Sea.

The Salish Sea

Located along the coast of the Pacific Northwest, the Salish Sea has been an important part of life for Coast Salish peoples and animals for millennia. Home to seals, orcas, salmon, sea lions, porpoises, sea otters, coastal wolves, and so much more, the Salish Sea has ecological and cultural importance. In various parts of this sea, you can find two different ecotypes of killer whales, several seal and sea lion species, and even the endemic coastal wolves, a subspecies of grey wolves that rely heavily on the Salish Sea.


Our oceans and seas are under attack from climate change, overfishing, and more. With rising sea levels, ocean acidification, and so much more, the underwater environment is starting to look drastically different and starting to become barren. As it covers 71% of the planet, the ocean helps regulate the planet’s climate, is home to millions of flora and fauna, and is an important part of many communities’ every day life.

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