The ocean is a massive body of saline water that covers approximately 72% of the Earth's surface. According to NOAA, there is only one Global Ocean. However, this ocean has been divided into distinct named geographic regions by countries and oceanographers. Today, most nations including the United States recognizes five ocean basins, namely Arctic, Atlantic, Indian, Pacific, and Southern. Together, they hold around 97% of the water found on Earth and significantly influence global weather patterns and food supply chains. The ocean houses a plethora of marine organisms ranging from marine microbes to the world's largest animal, the blue whale. However, although the ocean plays a major role in sustaining life on Earth, we have explored or mapped only about 20% of the ocean. The rest remains a mystery.
1. Arctic Ocean
The smallest, coldest, and shallowest of the oceans of the world, the Arctic Ocean is located in the Northern Hemisphere’s Arctic north polar region. The Arctic Ocean has a roughly circular basin that is nearly enclosed by the continental landmasses of North America, Eurasia, Greenland, and several smaller islands. The area occupied by the ocean is about 15,558,000 square km, and its coastline extends for 45,389 km. The maximum recorded depth is found to be 18,456 feet. The Bering Strait connects the Arctic Ocean to the Pacific Ocean. The Greenland Sea and the Labrador Sea forms the connection between this ocean and the Atlantic Ocean. The countries bordering the Arctic Ocean are the US, Canada, Iceland, Greenland, Norway, and Russia. Barrow and Prudhoe Bay in Alaska; Churchill, Nanisivik, and Inuvik in Canada; Nuuk in Greenland; Kirkenes, Vardø, and Longyearbyen in Norway; and several ports like Murmansk, Tiksi, and Pevek in Russia, all lie on the Arctic coast.
The Arctic Ocean is located in a polar climatic zone characterized by frigid year-round temperatures. Long hours of darkness engulf the ocean during winters and summers are characterized by continuous daylight. The marine habitat of the Arctic Ocean is a fragile ecosystem that is highly susceptible to slight disruptions in weather. Threatened species of whales and walruses inhabit the ocean. Plant life in the Arctic Ocean is scarce except for abundant volumes of phytoplanktons. The Lion’s mane jellyfish and the banded gunnel are among the few species of marine creatures inhabiting the Arctic Ocean’s waters. The ocean bed also hosts petroleum and natural gas fields, polymetallic nodules, and placer deposits.
Like other oceans of the world, climate change threatens to adversely affect the marine ecosystem of the Arctic Ocean. As per research, the Arctic might become ice-free by 2040. This transformation would load the Arctic with large volumes of meltwater and affect the ocean currents prevailing in the region. These alterations would, in turn, cause a drastic change in the global climate.
2. Atlantic Ocean
The Atlantic Ocean spans an area of 85,133,000 square km. The Atlantic Ocean is bounded by the landmasses of North and South America to the west and Asia and Africa to the east. The Arctic Ocean lies to its north, the Southern Ocean to its south, Pacific to the southwest and Indian Ocean to the southeast. The average depth of the Atlantic Ocean is 3,646 m and the Milwaukee Deep (8,380 m) in the Puerto Rico Trench, is its deepest known point.
Since the Atlantic Ocean is vast, its climate varies widely from the north to the south. Warm and cold ocean currents in the Atlantic also influence the climate of the coastal areas on the shores of the Atlantic. The Gulf Stream and the North Atlantic Drift are responsible for keeping large parts of the coast of north-western Europe and the British Isles warm when the coast of Newfoundland in Canada on the same latitude experiences extreme temperatures in winter.
The Atlantic Ocean has contributed significantly to the economy of many nations. Petroleum deposits on the Atlantic’s floor, precious stones, placer deposits, and polymetallic nodules are abundant. The Atlantic also hosts rich fishing resources with haddock, cod, mackerel, herring being the chief commercially important fish species.
Several rare and threatened species of marine life like sea turtles, whales, dolphins, manatees, seals, sea lions abound in the Atlantic. Frequent oil spills, municipal sewage pollution, industrial pollution, bycatch during irresponsible and outdated fishing activities all threaten the marine life in the Atlantic Ocean.
3. Indian Ocean
The Indian Ocean occupies 70,560,000 square km area on the Earth’s surface. The Eurasian landmass lies to the north of the Indian Ocean, Australia to the east, Africa to the west and the Southern Ocean and Antarctica to the south. 3,741 m is the average depth of the Indian Ocean, and its deepest point is Diamantina Deep. The depth in this region is 8,047 m.
The Indian Ocean region experiences a monsoon type of climate. Cyclones are common during the summer season. This ocean is also the warmest ocean in the world. The warm tropical waters of the ocean support a great diversity of life. The abundance of phytoplankton and aquatic flora supports a complex food chain. Thus, the Indian Ocean offers lucrative fishing grounds and fish, especially tuna and shrimp caught here, are sold to markets across the world. However, despite this great biodiversity, climate change is taking its toll on the Indian Ocean ecosystem. Overfishing in the waters is also disturbing the marine life in this part of the ocean.
4. Pacific Ocean
The largest region of the Global Ocean, the Pacific Ocean has the Arctic Ocean to the north, the Southern Ocean to the south, Australia, and Asia to the west and the Americas to the east. Spanning an area of 168,723,000 square km, the Pacific Ocean accounts for one-third of the total surface area of the planet. The deepest point in the Pacific Ocean is the Challenger Deep in the Mariana Trench (10,929 m) located in the western North Pacific.
Large parts of the Pacific remain unexplored due to its great depths. However, in the relatively shallow waters off the coast of Australia and New Zealand, petroleum and natural gas deposits have been discovered. Pearl extraction is also common in the Pacific's waters. A large variety of fish like tuna, salmon, swordfish, herring, snapper, etc., abound in parts of the Pacific.
Today, the Pacific Ocean and its marine life are not safe. A large number of highly polluted rivers from the countries of southeast Asia and east Asia drain into this ocean, contaminating the waters with pollutants. Fertilizer and pesticide wash-off from agricultural fields, sewage, and industrial wastes all drain into the ocean via these rivers. Excess of oxygen depleting pollutants triggers hypoxia and creates dead zones in the ocean. Overfishing in the Pacific has also depleted its marine wealth greatly. A number of rare and threatened species is getting depleted in large numbers as bycatch.
5. Southern Ocean
Encircling Antarctica, south of the 60° S latitude, is the Southern Ocean or the Antarctic Ocean. It is the southernmost of the 5 regions of the Global Ocean and the fourth largest of the five. Though the Southern Ocean does not have a landmass bordering it to the north, it is treated as a separate oceanic division due to the difference in water properties of the ocean south of the 60° S latitude. It is a deep ocean with depth ranging between 4,000 and 5,000 m across most parts.
Researchers estimate that the Southern Ocean seabed is a storehouse of massive oil and gas fields, valuable minerals like gold, placer deposits, manganese nodules, and more. The icebergs of the Southern Ocean are treated as freshwater resources, sufficient to feed every person on Earth for a period of several months. The Southern Ocean is also one of the most dangerous parts of the ocean for ships. Choppy seas, storms, and iceberg interventions are common. The remoteness also prevents rescue missions from reaching the ships in need.
The Southern Ocean is home to unique species specially adapted to survive the frigid weather conditions. Penguins, orcas, whales, seals, colossal squids are some of the most notable species of the Southern Ocean. A large number of migratory birds can be spotted in the oceanic region and Antarctica. These include terns, gulls, albatrosses, skuas, petrels, etc. Several threats are experienced by the marine inhabitants of the Southern Ocean. The Antarctic ozone hole in the ozone layer above allows harmful UV rays to reach the marine habitat, reducing phytoplankton by as much as 15%. Unregulated fishing also reduces the fish stock in the ocean which disturbs the food chain and affects the survival of the other species in the chain.