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Introducing the Pacific Ocean

We focus on learning about the largest ocean basin on the pl…

Coral reef in Sombrero Island, Philippines Jett Britnell - Ocean Image Bank

Written by

IOC-UNESCO

Publishing Date

27 April 2022

Reading time

10 min

Due to cultural, geographical and historical factors, we have “divided” the ocean into five ocean basins known as the Pacific, Atlantic, Indian, Arctic and Southern Oceans. In this article, we will focus on the largest ocean basin on the planet, the Pacific Ocean, and discover all its details and characteristics.

The Earth has one large ocean that connects the entire world and contains more than 97% of the total amount of water on the planet. The ocean is also the largest ecosystem on Earth, representing 99% of the entire biosphere, thus hosting a large number of species. This huge body of water is also known as the Global Ocean.

What is the largest ocean basin?

The largest ocean basin is the Pacific Ocean. Occupying nearly 32% of the Earth’s surface, the Pacific covers 165,250,000 square kilometers (63,800,000 sq. mi), and about 46% of the Earth’s water surface.

It extends from the western coasts of North, Central, and South America to Oceania, Asia, and Russia in the north, and contains about 30,000 islands divided between the regions of Polynesia, Melanesia, and Micronesia.
The Pacific also connects to the Indian Ocean basin near the Strait of Malacca, Sumatra, and to the Atlantic through the Strait of Magellan and the Drake Passage. Its maximum latitudinal extent reaches 19,000 km (12,000 mi) between the coast of Colombia and the Malay Peninsula.

The Pacific Ocean basin has twice the surface area and more than twice the volume of water as the second largest Atlantic. Interestingly, the area covered by the Pacific exceeds that of all the continents combined.

Oceano Pacifico_Decennio del Mare — Pacific Ocean Basin, Esteban Gottfried for IOC-UNESCO

Where does the name “Pacific Ocean” come from?

Its name comes from the fact that the Portuguese explorer Ferdinand Magellan, during his voyage to the Philippines, found the ocean quite calm, therefore “peaceful”.

How deep is the Pacific Ocean?

Il punto più profondo del bacino dell’Oceano Pacifico è conosciuto come Challenger Deep e si trova nella Fossa delle Marianne, ad una profondità di 11.034 m (36.201 piedi). È il punto più profondo registrato nel mondo, situato a est delle Filippine. È così profondo che il monte Everest entrerebbe nel Challenger Deep con oltre un miglio di margine!

The deepest point in the Pacific Ocean basin is known as the Challenger Deep and is located in the Mariana Trench, at a depth of 11,034 m (36,201 ft). It is the deepest recorded point in the world, located east of the Philippines. It is so deep that Mount Everest would fit into the Challenger Deep by over a mile!

How many “Pacific Oceans” are there?

The answer is one, but ocean circulation (caused by the Coriolis effect) divides it into two independent volumes of water that meet at the equator: the North Pacific Ocean and the South Pacific Ocean. The Galápagos and Gilbert Islands, despite straddling the equator, are considered entirely within the South Pacific.

The North Pacific is the part of the Pacific Ocean basin that lies north of the equator. It extends from the eastern coasts of Asia to the western coasts of North and South America (to the Equator) and extends north to the Arctic region.

The South Pacific lies south of the Equator, covers a significant portion of the Southern Hemisphere (SH) and plays an important role in the global climate system. In fact, the tropical Pacific Ocean functions as a self-regulating system of accumulation and release of heat, redistributing it towards the poles. Because it is a relatively stationary process, when the Pacific is overloaded with heat, it causes sudden warming episodes that increase the risk of extreme weather events.

Temperature

The ocean is stratified, and one of the main factors in this stratification is temperature: the deep waters, which make up about 80% of the ocean’s volume, are very cold, with temperatures remaining just above freezing, usually around 3.5 °C (38.3 °F). In the shallow zone, however, temperatures vary greatly down to a depth of about 300 metres (1,000 ft).

Typically, water temperatures in the North Pacific are slightly warmer than in the South Pacific. This is due to the lower land-to-sea ratio in the Northern Hemisphere than in the Southern Hemisphere, and the influence of Antarctica and the Southern Ocean.

Salinity

Given the vastness of the Pacific Ocean, its physical characteristics such as salinity are highly variable in both the western and eastern Pacific, due to seasonal changes in surface currents.
In general, the Pacific Ocean has a slightly lower salinity than the Atlantic Ocean, due to the presence of atmospheric precipitation. In the tropical and subtropical areas of the Pacific, in fact, precipitation is more intense and is associated with the monsoons of the region. Due to this phenomenon, salinity is generally lower in the equatorial area.
Salinity, together with temperature, is also a fundamental component in ensuring the exchange of oxygen and nutrients between surface waters and deeper waters.

The combination of salinity and temperature generate deep thermohaline currents which, together with the surface currents generated by the wind, give rise to the Great Global Conveyor Belt, a constant movement in the ocean around the globe. Cold, salty water forms at the poles and, due to its high density, sinks, while warm water that forms in the tropics, near the equator, is less dense and stays on the surface.

This movement is important for the entire planet, as it regulates the climate around the world and is also essential for the transport of oxygen and nutrients for marine and coastal ecosystems.

Climate

The weather patterns of the Northern and Southern Hemispheres generally mirror each other, but in the Pacific Ocean this is not the case.

In the North Pacific in particular, there are notable differences between the eastern and western regions at the same latitude: the extreme temperatures that characterize winters off the eastern coast of Russia, for example, contrast with the milder winters of British Columbia.

The tropical and subtropical areas of the Pacific Ocean are periodically affected by weather oscillations, lasting about three months, known as the El Niño and La Niña Southern Oscillations. Both El Niño and La Niña are periodic weather patterns that cause, respectively, the surface ocean waters of the southeast Hawaiian region to warm and cool: if it is more than 0.5 °C (0.9 °F) above or below normal for that period, then El Niño or La Niña is considered to be in progress.

The Pacific Ocean includes other weather phenomena, known as tropical cyclones. Among these, we recognize the Pacific hurricanes that normally originate in southern Mexico, sometimes, hitting the Mexican coast and sometimes the United States mainly between June and October. Typhoons that form in the Pacific Northwest affect Southeast Asia from May to December. While the Pacific Islands are occasionally subject to tropical cyclones that form in the southern basin.

Biodiversità

Of all the ocean basins, the Pacific boasts the greatest marine biodiversity. Currents that connect the southern and northern polar waters of the Pacific allow life from different ocean regions to come into contact with each other.

One of the main features of this diversity is the kelp forests, which are found on the cold-water rocky coasts of North and South America. These forest-like environments have almost as diverse an animal biodiversity as rainforests: they are home to a wide variety of marine life, from invertebrates to fish, mammals and seabirds.

In the tropical areas of the western Pacific, the richness of marine biodiversity increases exponentially. Here we can find the richest and most extensive coral reefs on the planet. The coral reefs of the South Pacific are low-lying structures that have developed on basaltic volcanic structures located beneath the surface of the ocean.

One of the most impressive coral reefs is the Great Barrier Reef off north-eastern Australia, which is made up of several chains of coral reefs.

Whales, sea turtles, dolphins, killer whales, otters and sea lions are an important and spectacular part of Pacific life.

Geology

Research has shown that all major features of the Pacific Ocean floor and the lands surrounding it have their origins in plate tectonics.

The “Ring of Fire”, a well-known feature of the Pacific, is the area where most of the world’s active volcanoes are located, most of which are underwater. The Ring of Fire is an arc of volcanic islands and deep trenches located in the western Pacific, in the area where two tectonic plates collide (convergent zone), sliding under each other. Due to this phenomenon, the Pacific Ocean basin is currently shrinking by about 2.5 cm (1 in) per year on three sides, averaging about 0.52 square kilometers (0.20 sq mi) per year. In contrast, the Atlantic Ocean is increasing in size.

On the opposite side, the East Pacific Rise is an active zone where new crust is being generated. In the southeast Pacific, the Nazca Plate and the South American Plate collide to form the Andes, and just offshore is the Peru-Chile Trench.

Because tectonic plates move so rapidly, earthquakes occur all along the Ring of Fire. It is no surprise that the strongest earthquakes ever recorded have occurred here.

The 1960 earthquake near Valdivia, Chile, was the most powerful in recorded history, registering a magnitude of 9.5 on the Richter scale.

Mineral resources

The Pacific Ocean contains interesting mineral resources, of which only a few have been exploited, such as salt, bromine and magnesium. There are also known natural gas deposits on the continental shelf of both the northern and southern hemispheres, while oil reserves have already been explored near Vietnam, the Philippines, Indonesia, California, Russia and China.
Minerals can be extracted directly from seawater, from alluvial deposits or from the continental shelf.

What challenges is the Pacific Ocean facing today?

One of the main problems, as is now clear, is marine pollution, mainly from solid waste such as plastic and other debris. In the Pacific, we find the largest garbage vortex, or plastic soup, also known as the “Great Pacific Garbage Patch“: it is a huge accumulation area of waste, including plastic, which is located in the center of the two circular currents (gyres) of the North and South Pacific.

Pollution is mainly caused by poor waste management (littering), shipping, mining and drilling, oil spills and ocean dumping – the direct discharge of pollutants into the ocean from industries, ships or sewage treatment plants.

Other serious threats to the balance of the Pacific Ocean are overfishing and illegal fishing practices, which destroy marine ecosystems and leave behind an incredible amount of harmful debris.